92
CONTENTS GASOLINE ENGINE GASOLINE ENGINE TROUBLESHOOTING ........................................................... 1 BASIC INSPECTION OF GASOLINE ENGINES .................................................... 2 1. INSPECTION OF INTAKE MANIFOLD VACUUM PRESSURE USING VACUUM GAUGE .................................................................................. 2 2. CYLINDER BALANCE TEST .............................................................................. 4 ENGINE BASIC COMPONENTS AND VALVE MECHANISM ................................ 5 1. COMPRESSION ................................................................................................. 5 2. COMPRESSION PRESSURE CHECK .............................................................. 7 3. CHECK VALVE CLEARANCE (EXCEPT VEHICLES WITH AUTO-LASH ADJUSTER) ....................................................................................................... 9 4. INSPECTION OF LASH ADJUSTERS ............................................................... 11 IGNITION SYSTEM ................................................................................................. 15 1. INSPECTION OF IGNITION SYSTEM ............................................................... 15 2. INSPECTION OF SPARK PLUGS ...................................................................... 18 3. IGNITION TIMING ADJUSTMENT ..................................................................... 20 FUEL SYSTEM ........................................................................................................ 21 1. FUEL SYSTEM INSPECTION ............................................................................ 21 2. MAJOR CAUSES OF MPI ENGINE PROBLEMS .............................................. 24 3. FUEL PUMP OPERATION CHECK .................................................................... 29 4. FUEL PRESSURE CHECK ................................................................................ 30 5. INJECTION SPRAY CHECK .............................................................................. 33 6. FUEL PRESSURE CHECK OF GDI ENGINE .................................................... 34 INTAKE SYSTEM .................................................................................................... 37 1. INTAKE SYSTEM SERVICE ............................................................................... 37 2. CLEANING VALVE AND SURROUNDING AREA IN THROTTLE BODY ........... 44 3. INSPECTION OF ISC SERVO ........................................................................... 44 4. ADJUSTMENT OF BASIC IDLE SPEED ........................................................... 45 5. EMISSION CONTROL SYSTEMS ..................................................................... 46

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Page 1: Troubleshooting Engines

CONTENTS

GASOLINE ENGINE

GASOLINE ENGINE TROUBLESHOOTING........................................................... 1

BASIC INSPECTION OF GASOLINE ENGINES .................................................... 21. INSPECTION OF INTAKE MANIFOLD VACUUM PRESSURE

USING VACUUM GAUGE .................................................................................. 22. CYLINDER BALANCE TEST.............................................................................. 4

ENGINE BASIC COMPONENTS AND VALVE MECHANISM ................................ 51. COMPRESSION................................................................................................. 52. COMPRESSION PRESSURE CHECK .............................................................. 73. CHECK VALVE CLEARANCE (EXCEPT VEHICLES WITH AUTO-LASH

ADJUSTER) ....................................................................................................... 94. INSPECTION OF LASH ADJUSTERS ............................................................... 11

IGNITION SYSTEM ................................................................................................. 151. INSPECTION OF IGNITION SYSTEM ............................................................... 152. INSPECTION OF SPARK PLUGS...................................................................... 183. IGNITION TIMING ADJUSTMENT ..................................................................... 20

FUEL SYSTEM ........................................................................................................ 211. FUEL SYSTEM INSPECTION............................................................................ 212. MAJOR CAUSES OF MPI ENGINE PROBLEMS .............................................. 243. FUEL PUMP OPERATION CHECK.................................................................... 294. FUEL PRESSURE CHECK ................................................................................ 305. INJECTION SPRAY CHECK .............................................................................. 336. FUEL PRESSURE CHECK OF GDI ENGINE .................................................... 34

INTAKE SYSTEM .................................................................................................... 371. INTAKE SYSTEM SERVICE............................................................................... 372. CLEANING VALVE AND SURROUNDING AREA IN THROTTLE BODY........... 443. INSPECTION OF ISC SERVO ........................................................................... 444. ADJUSTMENT OF BASIC IDLE SPEED ........................................................... 455. EMISSION CONTROL SYSTEMS ..................................................................... 46

Page 2: Troubleshooting Engines

DIESEL ENGINE

DIESEL ENGINE TROUBLESHOOTING ................................................................ 47

ENGINE BASIC MECHANISMS.............................................................................. 481. COMPRESSION PRESSURE INSPECTION (4D56) ......................................... 482. VALVE CLEARANCE ADJUSTMENT ................................................................ 49

FUEL SYSTEM ........................................................................................................ 531. FUEL SYSTEM PROBLEMS .............................................................................. 532. DRAINING WATER FROM FUEL FILTER .......................................................... 543. INSPECTION AND ADJUSTMENT OF INJECTOR NOZZLES ......................... 554. SELF-REGULATING GLOW SYSTEM ............................................................... 595. ELECTRONICALLY CONTROLLED EGR SYSTEM .......................................... 626. TURBOCHARGER ............................................................................................. 647. ELECTRONICALLY CONTROLLED FUEL INJECTION SYSTEM ..................... 65

Page 3: Troubleshooting Engines

TROUBLESHOOTING

TROUBLESHOOTING PROCEDURES .................................................................. 71

INTERVIEW ............................................................................................................. 73

TROUBLE REPRODUCING METHODS ................................................................. 75

POINTS TO RESPECT IN TROUBLE REPRODUCTION........................................ 75

SELF-DIAGNOSIS ................................................................................................... 77

BASIC FUNCTIONAL INSPECTION....................................................................... 78

ACTUATOR TEST .................................................................................................... 79

TROUBLESHOOTING TREE - GASOLINE ENGINE .............................................. 80

INSPECTIONS TO NARROW DOWN SUSPECT SYSTEMS.................................. 81

Page 4: Troubleshooting Engines

FOREWORD

This booklet is compiled for introducing the key points and service points of Engine trouble-shooting on Mitsubishi vehicles. The purpose of this book is to provide information fortraining and other service activities.All information in this book is current as of time of publication. We, however, reserve theright to make changes at any time without prior notice or obligation. For more detailedservice information, refer to the applicable Technical Information Manuals, WorkshopManuals, Service Bulletins and other service publications.

November 2001

INTERNATIONAL AFTER-SALES DEPARTMENT

MITSUBISHI MOTORS CORPORATION

© MITSUBISHI MOTORS CORPORATIONAll rights reserved. This book may not be reprodeced or copied, in whole or in part,without the written permission of Mitsubishi Motors Corporation.

Page 5: Troubleshooting Engines

Gasoline Engine

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Pub. No. PTEE0113

GASOLINE ENGINE TROUBLESHOOTINGThere are three important factors that are indispensable for the gasoline engine to be able to operate smoothly,run at idle properly, respond to accelerator control quickly, offers strong drive power, and operate on a mini-mum amount of fuel; these factors (called “three essentials”) are “sufficient compression pressure”, “strongsparks at proper timing”, and “appropriate air-fuel ratios”. Also essential in addition to the above-mentionedfactors is “proper operation of the emission control systems”.

1. Sufficient Compression Pressure

The compression pressure of the engine has direct effect on combustion pressures generated in cylinders. Ifit is poor, the engine will have difficulty in starting, run idle irregularly, produce only small power, and consumefuel excessively.

2. Strong Sparks at Proper Timing

Even when the compression pressure is sufficient and air-fuel ratio is appropriate, good engine operation isnot assured if the spark plugs generate only weak sparks. Strength of sparks is not all that is required of sparkplugs; spark generating timing is also very important. Difficulty in starting cold engines and misfire when idlingand during mid-range and high speed operation are often caused by some defect in the ignition system.Improperly operating ignition system also causes increased fuel consumption.

3. Appropriate Air-fuel Ratios

Different engine operating conditions require mixtures of different air-fuel ratios. If the mixture is too rich in acertain condition, the engine uses fuel wastefully. If the mixture is too lean, the engine can not produceenough power to accelerate the vehicle.

4. Proper Operation of Emission Control Systems

A malfunctioning emission control system may give adverse effects, especially to idle speed characteristicsand operation in the driving speed range.An engine will offer its full performance if it is assembled perfectly. As the engine is used over time, however,it will suffer faults mainly because of material fatigue, wear, vibration during driving, dust, ambient tempera-ture changes, humidity, engine temperature changes, use of poor quality fuel and oil, and overload conditionsthat may occur transiently. A fault may result from a multiple causes as well as a single cause. Also, a fault ina system may be caused by malfunction of another system that is directly linked to the system or has no directinteraction with it but can give some effect on it. In either case, the causes always relate to defects in one ormore of the factors “sufficient compression pressure”, “strong sparks at proper timing”, “appropriate air-fuelratio”, and “proper operation of the emission control systems”. It is, therefore, important for you to investigatefault conditions minutely with this in mind to be able to identify the system really responsible for a fault condi-tion and isolate the faulty components.

Three essentials for proper combustion

Sufficient compression

pressure

Appropriateair-fuel ratioStrong spark

GASOLINE ENGINE - Gasoline Engine Troubleshooting

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Pub. No. PTEE0113

GASOLINE ENGINE - Basic Inspection of Gasoline Engines

BASIC INSPECTION OF GASOLINE ENGINES

1. Inspection of Intake Manifold Vacuum Pressure Using Vacuum Gauge1) Normal vacuum pressure

During idling, the intake manifold vacuum pressure stays at around 65 kPa 50 cmHg. If the throttle valve isopened momentarily to the wide open position, the vacuum gauge needle will indicate the atmospheric pres-sure but, as soon as the throttle valve is moved back to the idling position, the gauge will indicate a vacuumpressure higher than 80 kPa 60 cmHg and then its indication will settle into the above-mentioned normalvacuum pressure.

Normal vacuum pressure

2) Abnormal vacuum pressure due to poor valve seating

During idling, the gauge indication fluctuates intermittently within a range of approximately 5 kPa 4 cmHg. Ifthe indication varies slowly between 50 and 60 kPa 38 and 46 cmHg, the problem is attributable to animproper air-fuel ratio.

Abnormal vacuum pressure due to poor valve seating

3) Abnormal vacuum pressure due to leakage of air through manifold connections

During idling, the vacuum pressure does not become higher than approximately 30 kPa 23 cmHg. As theamount of air leakage increases, the vacuum pressure level becomes closer to the atmospheric pressure andthe idle speed becomes unstable.If a lubricant or other liquid is sprayed over the area where a vacuum leakage is suspected, the engine idlespeed will increase.

Abnormal vacuum pressure due to leakage of air

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Pub. No. PTEE0113

GASOLINE ENGINE - Basic Inspection of Gasoline Engines

4) Abnormal vacuum pressure due to weak valve springs

The gauge needle swings quickly when the engine is revved up to a speed close to the maximum speed.

Abnormal vacuum pressure due to weak springs

5) Manifold vacuum check

(1) Before inspection, set the vehicle to the pre-inspectioncondition.

(2) Connect the MUT-II to the diagnosis connector.(3) Disconnect the ventilation hose from the positive crank-

case ventilation (PCV) valve, and then connect a vacuumgauge to the ventilation hose.

(4) Check that the idle speed is within the standard value.(5) Check the intake manifold negative pressure while the

engine is idling.

Limit:

ledoM tnuomamuucaV

RECNAL10' 1G4 IPM aPk06niM

TNALAG79' 6G4 aPk06niM

RECNAL69'AMSIRAC

9G4 aPk06niM

OREJAP10' 7G6

NOGAWECAPS89'TNALAG

6G4 IDG *)gHmm24(aPk65niM

AMSIRAC89' 9G4 aPk73niMedomnaeL

RATSECAPS99' aPk43niM

OREJAP10' 7G6 *aPk06niM

* Stoichiometric modeAfter 4 minutes or more have passed in the idle running condition

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Pub. No. PTEE0113

GASOLINE ENGINE - Basic Inspection of Gasoline Engines

Atmospheric pressure101 kPa = 760 mmHg = 1.03 kg/cm2

Note: Meaning of the Min. 60 kPa

Atmospheric pressure

Absolute pressure

Poor vacuum causing by worn out cylinder or piston rings.

Engine condition is good

Min. 60 kPa (451 mmHg)

Measured from atmospheric pressure

(101 kPa)

760 mmHg

2. Cylinder Balance Test1) Tracking faulty cylinder by causing misfire

With the engine running at idle, disconnect the high-tension cable from each spark plug one at a time to causemisfire. If disconnection of a cable causes nothing to change or only small change to operation of the engine,there is some problem in the corresponding cylinder.

2) Deduction of faulty cylinder by deactivating injectors using actuator test mode of MUT-II

.oNmetI metI erudecorptseT noitidnocnoitcepsnI airetircytluaf/lamroN

10 rotcejni1.oN 6rofrotcejnienoetavitcaeD.tietavitcaernehtdnasdnoces

ehtllaroferudecorpsihttaepeR(fI.rehtonaretfaeno,srotcejnirehto

gnildinisruccoegnahconsirotcejninanehwnoitarepo

ehtkcehc,detavitcaedynarofrednilycgnidnopserroc

).melborp

gnildi:enignE eht,lamronsienigneehtfIdluohsdeepsgnildi

deepsenigne(egnahcroelbatsnuemocebdluohs

ta)llatsdluohsenignefonoitavitcaedyreve

.rotcejni

20 rotcejni2.oN

30 rotcejni3.oN

40 rotcejni4.oN

50 *rotcejni5.oN

60 *rotcejni6.oN

* 6-cylinder engine

Flare nut

Ignition test

<Reference>

Ignition test for diesel engine to specify the faulty cylin-der

Ignition test used to identify faulty cylinder in diesel engines.When idling operation is out of order in a diesel engine, per-forming this test allows the cylinder with a problem to be iden-tified.Loosen the flare nut of an injection pipe to stop injection offuel into the combustion chamber. If no change occurs to ro-tation of the engine, the cylinder is responsible for the faultyidling operation.

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Pub. No. PTEE0113

GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

ENGINE BASIC COMPONENTS AND VALVE MECHANISM

1. CompressionCompression is one of the essential functions the engine must involve to generate power. Cylinder compres-sion should be checked with respect to the following points: Adequate compression pressure is achieved in every cylinder. There is no cylinder with a compression pressure significantly lower than the others.

1) Compression pressures are too low in all cylinders

Too low compression pressures in all cylinders indicate likelihood of excessive wear of pistons, piston rings,and cylinders. The valve mechanism rarely causes this problem although it can become the cause.However, the basic components of today’s engines are durable enough to maintain their initial performancefor more than 100,000 km, so it is proper for technicians to seek to find causes of a compression pressureproblem in other components before trying to repair a basic engine component.

2) Compression pressure is too low for a particular cylinder

When compression pressure is too low only in a particular cylinder, the components that are appropriate forinspection are the piston, piston rings, and the cylinder. The items that are also considered appropriate forinspection are poor seating of valves and damage to gaskets (which causes leakage of compression pres-sure).Poor seating of valve may result either from forcing up of a valve by a cam due to insufficient valve clearanceor from inadequate contact between the valve and its seat. It is important to discriminate these two causes.Most of engine malfunctions resulting from damage and/or wear of its basic components and faults in thevalve mechanism are accompanied by a deteriorated intake efficiency and compression pressure. They rarelycause engine stalls but always cause extreme difficulty in standing starts, irregular operation, and poor out-puts.Poor idling performance and irregular idling operation of engine result from inability of creating “even” and“sufficient” compression pressures in all cylinders due to a fault in the basic engine components and valvemechanism of the engine. It is necessary to measure the compression pressure, if fails to restore proper idlingperformance when performing idling adjustment. Overall decrease in the compression pressure often wors-ens startability and output performance of the engine, while uneven compression pressures between cylin-ders often adversely affects idling performance of the engine.Uneven compression pressures are attributable to both piston-/piston-ring-related problems and valve-mecha-nism-related problems. It is generally accepted practice to perform inspection of the valve mechanism prior toinspecting pistons and piston rings when uneven compression pressures are detected.

3) Possible causes of compression pressure problems

(1) If the compression pressure increases when a small amount of engine oil is poured into the combustionchamber Piston rings (breakage, wear) Cylinders (damage, wear)

(2) If the compression pressure is low only in a particular cylinder Cylinder head gasket (damage) Valve mechanism (bend, seizure, improper valve clearance) Rocker arms, camshafts (wear) Piston rings (breakage)

(3) If the compression pressure is too low almost evenly in all cylinders Valve timing (deviation from correct timing) Intake and exhaust systems (clogging)

(4) If the compression pressure is too high Carbon deposits in combustion chamber

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

4) Important inspection items for valve mechanism

Inspect the valve mechanism for the following items: Valve clearance Valve stems for seizure Deviation from correct valve timing Poor valve seating Wear of camshafts and cam lobes

It is necessary for achieving a sufficient compression pres-sure to assure gas-tightness between the cylinder and pis-ton and between the valve and its seat as well as to adjustthe valve timing properly.

Valve clearanceToo large or too small valve clearance results in impropervalve timing, which leads to poor engine output (due todeteriorated intake and exhaust efficiencies) and conse-quently increases in fuel consumption.

Fuel

con

sum

ptio

n g

/kw

h (g

/psh

) Valve clearance is normalValve clearance is too smallValve clearance is too large

Engine speed (r/min) x102

0 10 20 30 40 50

147(200)

340(250)

408(300)

5) Poorly synchronized valve timing

Valve timing problem does not occur so frequently. However, checking the timing belt for missing teeth is animportant inspection when a valve timing problem occurs.

6) Valve surging

Valve surging refers to uncontrolled opening and closing motion of the valve that occurs when the valve cannot follow the movement of the camshaft lobe during high-speed operation. If this phenomenon occurs, theoutput of the engine decreases due to lowered intake efficiency. Determining whether the valve surging istaking place in the engine is very difficult. One of the common method is to check the engine operatingcondition (acceleration) by driving the vehicle in the 2nd gear.Inspecting the valve springs for weakness and breakage should be performed when the engine is disas-sembled to find the cause of a valve surging problem.

<Reference>

Improper idling operation due to defective camshaft:If the base circle of the cam lobe is not round enough, thevalve timing may fail to be synchronized.Although you can not determine the cam profile, you can mea-sure the base circle diameter of the cam lobe.

Inspection method:Check the base circle portion of the cam lobe using a dialgauge for out-of-roundness. The needle of the dial gaugeshould not move.(The shape of the cam lobe differs with the engine model.)

Base circle

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Pub. No. PTEE0113

GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

1) Before inspection, check the engine oil, starter and bat-tery are normal. In addition, set the vehicle to the pre-inspection condition.

2) Remove all of the ignition coils and spark plugs.3) Disconnect the crank angle sensor connector.

NOTEDoing this will prevent the engine-ECU from carrying outignition and fuel injection while cranking the engine.

4) Cover the spark plug hole with a shop towel etc. and afterthe engine has been cranked, check that no foreign mate-rial is adhering to the shop towel.

Caution Keep away from the spark plug hole while crank-

ing. When cranking engine, if water, oil, fuel, etc., that

had entered into the cylinder, these materials willbecome heated and will gush out from the sparkplug holes, which is dangerous.

5) Set compression gauge to one of the spark plug holes.6) Crank the engine with the throttle valve fully open and

measure the compression pressure.

GDI engine

enignEledom

aPkeulavdradnatS aPktimiL ledoM

39G4 mpr003–0271 7331 NINIPOREJAP

mpr003–0271 2641 RATSECAPSAMSIRACYM0002

mpr003–9651 4331 AMSIRACYM89’

46G4 mpr003–0751 0121 RENNURECAPSNOGAWECAPS

TNALAG

47G6 mpr052–5721 089 OREJAP

MPI engine

enignEledom

aPkeulavdradnatS aPktimiL ledoM

1G4 mpr052–8261 5811 RECNAL

6G4 mpr004ot052–0531 0201 TNALAG

9G4 mpr004ot052–0731 0401 TNALAG

21A6 mpr004ot052–0731 0401 TNALAG

7G6 mpr004ot052–7711 578 OREJAP

7) Measure the compression pressures for all the cylinders,and check that the pressure differences of the cylindersare below the limit.

Limit: Max. 100 kPa

2. Compression Pressure Check

Crank anglesensorconnector

Compression gauge

9EN0872

9EN0759

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Pub. No. PTEE0113

GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

8) If there is a cylinder with compression or a compressiondifference that is outside the limit, pour a small amount ofengine oil through the spark plug hole, and repeat theoperations in steps (6) and (7).i. If the compression increases after oil is added, the

causes of the malfunction is a worn or damaged pis-ton ring and/or cylinder wall.

ii. If the compression does not rise after oil is added, thecause is a seize or defective valve seat, or pressure isleaking from the gasket.

9) Connect the crank angle sensor connector.10)Install the spark plugs.11)Install the ignition coil and connect the ignition coil con-

nection.12)Use the MUT-II to erase the diagnosis codes.

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

(1) Start the engine and allow it to warm up until the enginecoolant temperature reaches 80 to 90°C.

(2) Remove all spark plugs from the cylinder head for easyinspection.

(3) Remove the rocker cover.(4) Turn the crankshaft clockwise until the notch on the pulley

is lined up with the “T” mark on the timing indicator.

3. Check Valve Clearance (Except Vehicles with Auto-Lash Adjuster)

(5) Move the rocker arms on the No. 1 and No. 4 cylinders upand down by hand to determine which cylinder has its pis-ton at the top dead center on the compression stroke. Ifboth intake and exhaust valve rocker arms have a valvelash, the piston in the cylinder corresponding to theserocker arms is at the top dead center on the compressionstroke.

(6) Valve clearance inspection and adjustment can be per-formed on rocker arms indicated by white arrows whenthe No. 1 cylinder piston is at the top dead center on thecompression stroke, and on rocker arms indicated by solidarrows when the No. 4 cylinder piston is at the top deadcenter on the compression stroke.

(7) Measure the valve clearance.If the valve clearance is not within the standard value,loosen the rocker arm lock nut and adjust the clearanceusing a thickness gauge while turning the adjusting screw.

Standard value (hot engine):4G1 engine models (Including KUDA)

Intake valve 0.20 mmExhaust valve 0.25 mm

PAJERO io 4G18 engine modelsIntake valve 0.20 mmExhaust valve 0.30 mm

4G9 engine modelsIntake valve 0.20 mmExhaust valve 0.30 mm

01U0100

4G1 (12 valve SOHC)

PAJERO io 4G18 (16 valve SOHC)

W6015AL

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

(8) While holding the adjusting screw with a screwdriver toprevent it from turning, tighten the lock nut to the specifiedtorque.

Tightening torque: 9 ± 1 Nm

(9) Turn the crankshaft through 360° to line up the notch onthe crankshaft pulley with the “T” mark on the timing indi-cator.

(10)Repeat steps (7) and (8) on other valves for the clear-ance adjustment.

(11)Install the rocker cover.(12)Install the spark plugs and tighten to the specified torque.

Tightening torque: 25 ± 4 Nm

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

4. Inspection of Lash AdjustersPerform the inspection of the items shown below if the engine makes chattering noise that is seeminglycaused by malfunction of a lash adjuster immediately after start of the engine and the noise lasts thereafter.

NOTE(1) When the vehicle is parked on a slope for long time, the oil in each lash adjuster decreases, possibly

allowing air to enter the high-pressure chamber at the time of restarting.(2) After long-time parking, the oil in the lash adjuster piping may be partially lost. Since it takes some time for

lash adjusters to be supplied with oil at restart of the engine after this condition has occurred, air may enterthe lash adjusters.

(3) If noise results from the conditions of (1) and (2) above, the problem can be resolved by bleeding air out ofthe lash adjusters.

(4) Noise originating from malfunctioning lash adjusters begins immediately after start of the engine and itssound varies with increase and decrease of the engine speed but does not vary with change in the amountof load on the engine.

(5) Noise will barely stop during warm up operation at idle speed if its cause is a malfunctioning lash adjuster.However, it may stop only if the noise is caused by seizure of lash adjusters due to oil sludge accumulatedas a result of poor lubrication maintenance.

1) Functional inspection

(1) Start the engine.(2) See whether the engine generates noise immediately after a start and, if it is the case, whether the sound

of the noise varies with the speed of the engine.If the engine does not generate noise immediately after starting or the sound of noise does not changewith engine speed, the cause of the noise is not present in lash adjusters, so perform further inspection fornoise sources. When the sound of the noise does not vary as the engine speed changes, a problem in acomponent other than the engine components may be the cause. (The lash adjusters can be considerednormal in this case.)

(3) With the engine running at idle, see whether the sound level of the noise changes when the load on theengine is changed (by shifting the selector lever from N to D, for example). If the sound level changes withthe amount of load, possible causes may be metal-against-metal hitting sound resulting from worn crank-shaft bearings and/or connecting rod bearings. (The lash adjusters can be considered normal in thiscase.)

(4) Idle the engine after warm up and listen to abnormal noise. If the sound level of the noise does not change,proceed to step (5). If the sound weakens or disappears, the cause of the noise may be sticky lash adjust-ers due to oil sludge or other contaminants present in them. Perform a leak-down test in this case. (See therelevant Engine Workshop Manual.)i. Replace a defective lash adjuster.ii. If all the lash adjusters are normal, search for other causes of the noise.

Caution:Air bleed completely every new lash adjuster in isolation before installing it on the engine. (See therelevant Engine Workshop Manual.)

(5) Operate the engine to bleed air out of the lash adjusters.(6) If the engine is till generating noise, perform a leak-down test. (See the relevant Engine Workshop Manual.)

i. If only one lash adjuster is malfunctioning, replace it with a new one.ii. If two or more lash adjusters are malfunctioning, the possible cause may be a clogged oil passage.

Check the oil passages in the cylinder head and clean any clogged passage. If there is no cloggedpassage, replace the malfunctioning lash adjusters.

iii. If all the lash adjusters are normal, perform inspection in search for other sources of noise.

Caution:Air bleed completely every new lash adjuster in isolation before installing it on the engine. (See therelevant Engine Workshop Manual.)

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

(7) Start the engine and make sure the engine generates noiseany more. If necessary, continue operating the engine untilair is bled out of the lash adjusters.

NOTEThe lash adjusters on a DOHC engine can be replacedeasily by following the procedure shown below.

i. Hold down the valve using the special tool (Valve lifter),then remove the roller rocker arm.

Caution:Before performing the above operation, be sure tobring the piston in the relevant cylinder to a downposition by turning the crankshaft in order to pre-vent the held down valve from interfering with thepiston.

Any rocker arm can not be removed if it is lifted by acam. Before removing a rocker arm, rotate the cam-shaft to a position where the corresponding cam doesnot lift the rocker arm.

ii. Pull the lash adjuster out of the cylinder head.iii. Install in the cylinder head a new lash adjuster that

have been air-bled.iv. Hold down the valve using the special tool (Valve lifter),

then install the roller rocker arm.

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

2) Lash adjuster simple check (SOHC-16 valves)

(1) Stop the engine.(2) Remove the rocker cover.(3) Set the No. 1 cylinder to the compression top dead center

position.(4) Check the rocker arms to indicated by while arrows in the

illustration by the procedures given below.

<Checking an intake-side rocker arm>

Check whether the rocker arm moves downwards whenthe part of the rocker arm which touches the top of thelash adjuster is pushed.i. If the rocker arm moves down easily when it is pushed,

make a note of which is the corresponding lash ad-juster.

ii. If the rocker arm feels extremely stiff when it is pushedand does not move down, the lash adjuster is normal,so check for other cause of the problem.

<Checking an exhaust-side rocker arm>

NOTEIt will not be possible to depress the Y-shaped rocker armat the exhaust valve side if one lash adjuster is defectivebut the other one is normal. In such cases, carry out thefollowing procedure using a thickness gauge.

i. Check that a thickness gauge with a thickness of 0.1 –0.2 mm can be inserted easily between the valve andthe lash adjuster.

ii. If the thickness gauge can be inserted easily, make anote of which is the corresponding lash adjuster.

iii. If the thickness gauge can not be inserted easily, thelash adjuster is normal, so check for some other causeof the problem.

(5) Slowly turn the crankshaft 360° in the clockwise direction.(6) Check the rocker arms indicated by black arrows in the

illustration in the same way as explained in step 4.

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GASOLINE ENGINE - Engine Basic Components and Valve Mechanism

3) Simple lash adjuster inspection (DOHC)

(1) Stop the engine.(2) Remove the rocker cover.(3) Bring the No. 1 cylinder piston to TDC on its compression

stroke.(4) Check the rocker arms indicated by the white arrows in

the illustration as follows:Push by hand the portion just above the lash adjuster ofeach rocker arm to see whether the rocker arm can belowered.i. If any of the rocker arms can be lowered easily, take a

note of the corresponding lash adjuster.ii. If a rocker arm can not be lowered (feels very stiff when

pressed), the corresponding lash adjuster is normal.Perform further inspection in search for other causesof the noise.

(5) Rotate clockwise the crankshaft slowly a complete turn(360°).

(6) Perform the same procedure as in step (4) for the rockerarms indicated by the black arrows.

Front

4) Operating engine for bleeding air out of lashadjusters

(1) Check the engine oil. If necessary, add or change the oil.(2) Idle the engine for 1 to 3 minutes to warm it up.(3) With the engine under no load, repeat the operation cycle

shown in the diagram while listening to noise. (The noiseshould generally disappear when the operation cycle isrepeated 10 to 30 times. If the noise does not disappeareven after more than 30 cycles of operation, it is attribut-able to a cause other than air in lash adjusters.

(4) After the noise has disappeared, repeat further 5 cyclesof air bleeding operation.

(5) Run the engine at idle for 1 to 3 minutes to make sure thenoise problem has been completely resolved.

Air bleeding operation cycle

Open throttle valve slowly.

Approx. 3000 r/min

Close throttle valve.

Idle speed

15 sec. 15 sec.

One cycle 7FU0259

Page 20: Troubleshooting Engines

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Pub. No. PTEE0113

GASOLINE ENGINE - Ignition System

IGNITION SYSTEM

1. Inspection of Ignition System1) Key points for inspection

Until now, ignition system faults have taken forms of misfires and incomplete combustion which are attribut-able to insufficiently strong sparks. With recent high-performance ignition systems, however, it is almost usualthat normal systems always generate adequately strong sparks and abnormal systems do not generate sparksat all. The ignition timing is also an important factor fault of which has direct consequence of improper com-bustion.When the engine stalls, the cause can be often determined by performing the inspections (1) to (4) shownbelow. It is important here to note that if a fault occurs in an electrical system like the ignition system, thesymptom appears not only as an invariable fault state but also as a transient fault state. Some problems do notappear when the system is operating under stable conditions but appear when the system is subjected toexternal vibration or temperature changes. If the engine stalls frequently, these inspections should be per-formed while giving necessary vibration. Power transistors and ignition coils should be inspected with changesin the temperature taken into consideration.It is also useful to remember that with MPI and GDI engines, the crank angle sensor (or TDC sensor) signal isused both as engine speed signal and ignition timing signal. Problem involved in this signal, therefore, maylead to engine stalls.

(1) Inspection of power transistor and ignition coilA simple method of this inspection is to see whether a spark jumps to the secondary circuit.

(2) Inspection of terminal connections for poor contact and/or looseness(3) Inspection of blown fuse in ignition switch IG circuit

When this fuse has blown, the engine can be cranked by the starter motor but it stalls when the ignitionswitch is turned to the ON position.

(4) Inspection of high-tension cables and spark plugs

<Reference>

Spark tests using resistive (high tension) cablei. Disconnect the resistive cable (center cable) from the distributor and keep its end a certain distance

(approx. 8 to 10 mm) away from the grounding earth. Then crank the engine to make sure a strong sparkjumps.

ii. Disconnect the resistive cable from a spark plug and keep its end away from the grounding earth in thesame manner as i. above. Then crank the engine to make sure a strong spark jumps.

iii. Remove a spark plug from the engine, connect it to the resistive cable and connect the ground electrodeto the ground. Then crank the engine to make sure a strong spark jumps.Any of the above tests must be completed in a short time.

<Reference>

Points to note when installing spark plugsIn engines with a spark plug located in the top of each combustion chamber (DOHC engines, for example),take special care to avoid letting any of the spark plugs hit the cylinder head or other engine parts and, as aresult, narrowing or reducing to zero the spark plug gap. If the spark plug gap is insufficient, the ignitionvoltage becomes too low to generate adequately strong spark. Especially, this causes misfire when the mix-ture is lean.

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GASOLINE ENGINE - Ignition System

2) Cylinder balance test

Inspection using a timing lightConnect a timing light to the high-tension cable for a cylinder.If the timing light does not flash or flashes irregularly, the igni-tion circuit for the cylinder is faulty. Perform the same test forall the remaining high-tension cables.

3) Inspection of ignition system

If a fault disables the ignition system from generating “strong sparks at proper timing”, the engine operatesirregularly when idling. Most typical of the faults that cause failure of generating strong sparks are decrease inthe amount of the primary current and leakage of current from the ignition coil secondary circuit, both resultingfrom defects in the ignition coil itself, high-tension cables, and spark plugs. Deposits on a spark plug andappearance of its electrode surfaces often give good criteria for determination of the condition of the sparkplug.

(1) Weak sparks

Today’s engines are equipped with high-performance and highly reliable ignition system thanks to intro-duction of fully transistorized and electronically controlled circuits. The spark plugs, however, have to besupplied with high secondary voltage only through resistive (high tension) cables, which means a misfiremay occur during high-speed driving if any of the resistive (high tension) cables is faulty.

i. Strong sparks can not be obtaineda. Amount of primary current insufficient

Insufficient amount of the primary current and consequent poor rise in the secondary voltage oftenresults from abnormal increase in the resistance of the primary circuit mainly due to poor contact.Other typical causes are as follows: Improper wiring of primary circuit Defective power transistor Defective ignition coil

b. Too low power supply voltageIf the amount of charge of the battery drops in cold temperatures, ignition system voltage highenough to make the engine start is not available. Since the amount of the primary current is smallin this condition, the secondary voltage also becomes low.

c. Too large resistance or leakage of current in secondary circuit The resistance increases and/or current leakage occurs in the secondary circuit if the rotor and/

or cap of the distributor are cracked, scratched, dirty, burnt, or corroded. They prevents suffi-ciently high secondary voltage from being supplied to spark plugs.

Resistive cables are defective. If the resistance of any resistive (high tension) cable increasesbeyond the limit, the secondary voltage drops. Defective insulation of the cables causes currentleakage.

d. Defective spark plugsWeak sparks result from improper spark plug gap and foulding. Carbon foulding

Carbon foulding may result from the following causes:Long-time idling or low-load, low-speed operationIncorrect heat range resulting in failure in reaching to a self-cleaning temperature (450 – 950°).Too rich mixtureIncomplete combustion

Oil fouldingOil working its way up or down into combustion chamber is the typical cause of oil foulding.

Timing light

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GASOLINE ENGINE - Ignition System

ii. Reach (length of threaded portion) of spark plug is too shortIf its reach is too short, the position of the center electrode in the combustion chamber is too away fromthe chamber wall. This causes poor combustion and thus low output power. It is very important to makesure that the spark plugs installed in an engine is those specified for the use with the engine.

<Reference>i. Main causes of misfire:

Large primary circuit resistance result in insufficient amount of primary circuit current. This lowers thevoltage induced in the secondary circuit and makes misfire tend to occur.

When the engine is operating under large load, it draws increased amount of air and must compressthe mixture to a higher pressure. To ignite such a mixture properly, the ignition system must generatehigher secondary voltage. If the secondary voltage is insufficient during high-load engine operationdue to a fault in the ignition system, misfire is likely to occur.

ii. Engine load and ignition timing:During high-load operation, the engine draws larger amount of mixture into the cylinders and compressesthe mixture to a high pressure. As increase in the compression pressure causes the ignition time lag to beslightly shortened, a control is made to retard the advance angle. Increased compression pressure alsocauses the flame propagation speed (burning velocity) to increase, which requires ignition timing adjust-ments to ensure proper operation of the engine.

(2) Affection of improper ignition timing

i. Ignition timing and fuel consumptionAny retard from proper ignition timing causes decreasein the engine output power and increase in the fuelconsumption. It also causes incomplete combustionand misfire during quick acceleration, detracting fromsmooth pick up of speed.

Normal5° advance5° retard

Ignition timing and constant-speed fuel consumption

Vehicle speed (km/h)Con

stan

t-sp

eed

fuel

co

nsum

ptio

n km

/dm

3 (km

/L)

20

23

20

15

10

40 60 80 100

ii. Operational defects resulting from improper ignition timingImproper ignition timing causes abnormal combustion with resultant misfire and disorderly operationof the engine.The ignition timing sometimes may get out of adjustment when the distributor is removed and thenreinstalled. If the ignition timing is too advanced, the engine tends to knock; if it is insufficiently ad-vanced, after-fire and overheating have tendency to occur. In either case, the output of the enginedecreases. Remember that if the ignition timing of the engine on an automatic transmission vehicle isretarded excessively, the engine speed decreases during a stall test; be careful not to take it as a faultof the torque converter.

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GASOLINE ENGINE - Ignition System

2. Inspection of Spark Plugs1) Spark Plugs for GDI Engines

Mitsubishi GDI engines use special spark plugs which are necessary for them to achieve ultra-lean combus-tion.

(1) The GDI engine spark plugs features

i. Larger projection of the center electrode (project type)ii. Platinum plated iridium center electrode that is highly resistant to heat (or wear)iii. Two-stage thermal design with a space provided between the center electrode and insulator for im-

proved anti-foulding performanceiv. Surface-gap design with two side electrodes that improves anti-foulding (carbon burning away) perfor-

mance.There are two types of spark plug for GDI engine: one featuring i, ii, and iii and the other featuring i andiv.

(Amount of projection changed)

5 3

(2) What does result from use of inappropriate spark plugs?

Many people may think that a cold-type plug with high heat range is appropriate for all engines since itsperformance is higher than a hot-type plug. However, if the heat range of the plugs is too high for theengine in which they are used, the temperature of the plugs rises insufficiently so that carbon or oil fouldingoccurs when the engine is idling or in low-speed operation. If the heat range is too low, the plugs areheated too high a temperature and may cause abnormal combustion, such as preignition and in the worstcase the electrodes could melt down, which could directly result in engine breakdown.The other important thing to note about spark plugs is that newer vehicles use resistor spark plugs thatincorporate resistors for the purpose of preventing electromagnetic interference. If any of these plugs arereplaced with a one that is of the same heat range and plug gap but has no internal resistance, the noiseit generates may cause erroneous operation of the engine-ECU or even destroy an electronic odometer.(Spark plugs with resistors are identified by letter R in the model number.)

(3) How should appearance of spark plug be interpreted?

i. What does a light brown color indicate?... It indicates that the engine is in good condition and the plug’s heat range is correct.

ii. What does a white color indicate?... It indicates too low heat range of the plug, likelihood of overheated engine, or too lean mixture.

iii. What do white deposits indicate?... White deposits will result from burning of oil. The cause is excessive oil entering combustion cham-ber.

iv. What do black dry deposits indicate?... They will result from too high heat range of plug or too rich mixture.

v. What do black wet deposits indicate?... They indicate that the plug is not firing or excessive oil is entering combustion chamber.

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GASOLINE ENGINE - Ignition System

2) Inspection, cleaning, and replacement of spark plugs

(1) Standard plugs (including two-electrode, surface-gap types)

i. Visually check the electrodes for burning damage, the insulator for cracks, and the plug tip for abnor-mal appearance.

ii. If the plugs is foulded, clean it using a spark plug cleaner or wire brush.iii. Check the spark plug gap using a plug gap gauge. If the gap is not up to specification, correct the

electrode spacing.

(2) Platinum-tipped plugs (including spark plug for GDI engine)

i. Visually check the electrodes for burning damage, the insulator for cracks, and the plug tip for abnor-mal appearance.

ii. If the plug is badly foulded, clean it with a plug cleaner. Complete it in a short time (less than 20seconds) to avoid damaging the platinum-plated tip. NEVER use a wire brush.Unlike other types, normal spark plug for GDI engine may be carbon foulded showing black appear-ance. Being of a special platinum-tipped type, however, any spark plug for GDI engine in such a condi-tion requires no cleaning or replacement as long as its insulation resistance is sufficient.

Insulation resistance: 10 MΩ or more

iii. Check the spark plug gap using a plug gap gauge. If the gap exceeds the limit, replace the plug.

Plug gap gauge

Move gauge in these directions.

Checking insulation resistance

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GASOLINE ENGINE - Ignition System

1) Before inspection, set the vehicle to the pre-inspectioncondition.

2) Connect the MUT-II to the diagnosis connector.3) Set up a timing light.4) Start the engine and run at idle.

–10 20 50Transmission oil temperature °C

600

700

800

900

Idle speed r/min

2010064

3. Ignition Timing Adjustment

5) Check that engine idle speed is within the standard value.

Standard value <GDI>:

smetI )mpr(deepseldI gnimitnoitingI ledomelciheV

39G4 )T/M(noissimsnartlaunaM 006 ± 008–05 ± *05 61.xorppA ° CDTB AMSIRAC

)T/A(noissimsnartcitamotuA 056 ± **mpr05

46G4 noissimsnartlaunaM 006 ± **mpr001 02.xorppA ° CDTB NOGAWECAPS

noissimsnartcitamotuA 056 ± **mpr001

47G6 noissimsnartlaunaM 006 ± ***mpr001 31.xorppA ° CDTB OREJAP

noissimsnartcitamotuA 02.xorppA ° CDTB

NOTE*: The idle speed in vehicles with manual transmission varies as shown in the table above in accordance with

the transmission oil temperature. (4G93)**: After 4 minutes or more have passed in the idle running condition, the idle speed will become 750 rpm.

(4G93), 700 rpm (4G64)***: After 4 minutes or more have passed in the idle running condition, the idle speed will become 700 ± 100 rpm

(6G74)

6) Select No. 17 of the MUT-II actuator test.

NOTEAt this time, the engine speed will become approximately 750 rpm (4G64, 4G93), 700 rpm (6G74).

7) Check that ignition timing is within the standard value.

Standard value: 5° BTDC ± 3°

8) If the basic ignition timing is outside the standard value, inspect the GDI, MPI system.9) Press the MUT-II clear key (Terminate the forced activation) to release the actuator test.

CautionIf the test is not canceled, a forced activation will continue for 27 minutes. Driving under thiscondition may damage the engine.

10)Check that ignition timing is at the standard value.

Standard value <MPI>:

enignE )mpr(deepseldI gnimitnoitingI ledomelciheV

1G4 057 ± 05 01.xorppA ° CDTB RECNAL

6G4)T/M(9G4)T/A(9G4

057 ± 001057 ± 05008 ± 05

TNARAG

1A6 056 ± 001 7.xorppA ° CDTB

7G6 007 ± 001 51.xorppA ° )27G6(CDTB01.xorppA ° )47G6(CDTB

OREJAP

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Pub. No. PTEE0113

GASOLINE ENGINE - Fuel System

FUEL SYSTEM

1. Fuel System Inspection1) General

The engine will become difficult to start if correct air-fuel mixture is not achieved due to faults in the fuelsystem.If a failure exists in the fuel system, the engine often exhibits apparent symptoms and their causes are ofteneasy to identify. Such causes include “no or insufficient fuel supply,” “mixture not rich enough for the engine tostart,” and “mixture too rich for the engine to start.” Therefore, it is important to correctly identify the types offault symptom.

(1) No or insufficient fuel supply

Fuel pump malfunction Clogged fuel filter or fuel line

(2) Mixture not rich enough for the engine to start

i. If the engine will not start in the morning, especially when the ambient temperature is low, this is oftencaused by incorrect quantity fuel being injected.Specifically, when the engine is cold and is difficult to start, some of the typical causes include thefollowing: Only a small amount of gasoline can evaporate due to low engine temperature. At a low engine temperature, increased viscosity of oil causes the engine to have higher internal

resistance. The engine then operates at a slower speed accompanied by slower flow of air, whichmakes gasoline be atomized insufficiently.

On the other hand, excessively rich mixture causes wet plugs, resulting in poor engine starting.ii. Percolationiii. Icing

(3) Poor gasoline quality

Poor engine starting can also be caused by use of low quality gasoline or gasoline containing impurities.This is especially true with the MPI/GDI engines. If this is the case, replacing the gasoline will solve theproblem. Before replacing the fuel, explain to the customer the reason and get his/her agreement.

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GASOLINE ENGINE - Fuel System

2) Insufficient fuel supply

Everyone knows that “the engine stops if the supply of fuel is cut.” The bottom line is that you should identifywhy fuel supply is interrupted. The engine will stall when a fuel supply system component is faulty, but alsowhen the fuel tank is empty.If supply of fuel is interrupted, the engine loses power and “shakes” for a few seconds before stalling. On theother hand, if a fault occurs in the ignition system described earlier, the engine stops instantly.Thus, probable cause of a fault can be determined by checking how the engine stalls. Also, checking how theengine behaves when it is restarted after a stall tells you if the stall has been due to excessively rich mixtureor interruption of fuel supply.

(1) Fuel tank and fuel cap

i. Impurities in fuel tankWater and other foreign matter present in the fuel tank can cause the engine to stall.Engine stalls caused by impurities in fuel occur more often when the fuel level is low than when the fueltank is full. This is because light foreign matter remains suspended in the upper portion of the fuelwhen the tank is full, but it goes down as the fuel level drops and then is pumped together with fuel intothe fuel main pipe, eventually clogging the pipe. What the customer experiences at that time is simplya “sudden engine stall.” As such is all the answer expectable from the customer when you interviewhim/her about the stall, you should do the following in an attempt to locate the cause.Check the fuel level, and prepare a polyethylene bucket or similar container large enough to hold theamount of fuel remaining in the tank. Drain out all fuel through the drain plug, and inspect both the fuelin the container and the fuel tank for contamination. If the fuel tank is found contaminated, remove thetank from the vehicle and clean it.Water and other impurities (fine dust particles, sticky substance, etc.) can pass through the in-tankfilter together with fuel, so they may have flown through the piping and fuel filter, and have reached theinjectors. Therefore, the entire fuel system needs to be checked.

ii. Faulty fuel tank capIf a vacuum is created in the fuel tank, fuel will not be sent out of the tank even when the fuel pumpfunctions normally; this then leads to an engine stall. To prevent vacuum forming in the fuel tank, thefuel tank cap is provided with a vacuum valve.If the vacuum valve fails to prevent a vacuum in the tank properly, the engine will stall. When youattempt to reproduce an engine stall condition caused by a vacuum in the tank, keep in mind that itoccurs most often when the engine is running under large load.

(2) Fuel lines

Inspect the fuel lines for air sucking into them through connections (engines with a carburetor) and heat-induced vapor lock.

<Reference>

Fuel supply rateIf a fault occurs in the fuel supply system while driving in either the first or second gear with the acceleratorfully depressed, the engine fails to rev up to its maximum speed or stalls like when it runs out of fuel.

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GASOLINE ENGINE - Fuel System

<Reference>

(1) Fuel tank cleaningThe fuel tank can be cleaned as follows:Remove the fuel tank from the vehicle. Refill the tank with1 – 2 dm3 (1 – 2 liters) of fuel, and shake the tank severaltimes before draining the fuel into a separate container.Repeat this over and over again. While doing this, be sureto keep flames away.

(2) Fuel line cleaningFuel line can be cleaned as follows:Remove the fuel hose between the fuel tank and fuel pipe.Remove also the fuel hose inside the engine compart-ment. Attach clean cloth to the end of the fuel pipe. Usingan air gun, blow compressed air from the tank end of thefuel pipe.Repeat this process while replacing the cloth until newcloth does not collect dust and other foreign matter anymore.

Cloth Air gun

<Reference>

As explained earlier, the first step in troubleshooting an MPI engine is to determine whether the mixture at thetime a problem occurs is “too lean” or “too rich.” The following two methods can be used to determine thecondition of mixture.(1) Determining based on visual check result and tester indication

i. CO and HC metersThese meters can be used to determine whether the problem is caused by a misfire or excessively richmixture.

ii. MUT-IIIndication of O2 sensor output voltage on the MUT-II provides means of determining whether themixture is lean or rich.

iii. OscilloscopeThe injection time indicated on an oscilloscope provides means of determining whether the mixture islean or rich.

iv. Exhaust colorIf the engine emits black smoke, the mixture is too rich.

v. Spark plug appearanceBurning or foulding condition of spark plugs gives a hint to determination of the mixture condition.

(2) Determining based on change in idling operation when fuel injection quantity is increased and decreasedi. Letting air into an air intake system portion downstream of the air flow sensor

If the idling condition improves, the mixture is too rich.ii. Using water temperature sensor

Disconnect the water temperature sensor from its connector and connect in place another water tem-perature sensor. Changing the sensor output by submerging the sensor in water of different tempera-tures enables the injection quantity to vary.

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GASOLINE ENGINE - Fuel System

2. Major Causes of MPI Engine ProblemsStartability related problems that can occur in MPI engines are classified into two types.If an MPI engine does not crank normally, inspect the starting system and engine basic components in thesame manners as those for other types of engine. If the engine cranks normally but hesitates to start, carryout checks appropriate for the accompanying symptoms, most of which are typical of the MPI engine. Appro-priate checks include determining whether the electric pump sends out fuel properly, the engine-ECU controlsfuel injection quantity correctly, and fuel does not dribble from an injector after injection.

1) Fuel supply system

The MPI engines use an electric fuel pump. Therefore, simply cracking the engine can not start it unless thepump supplies the engine with fuel. If the engine makes the first combustion or keeps rotating for a whilebefore stalling, for example, these symptoms may indicate particular problems in the fuel supply system.

Does not start (starting difficulty)

Difficult to start in low temperatures

Difficult to restart after warmed-up

OR OR

(1) Does not start (starting difficulty)

i. This problem occurs when fuel is not distributed to the injectors, or the fuel supply pressure is too low.If the engine does not start, perform the following inspection.

Check the fuel pressure to make sure fuel is distributed to the injectors.

Check the injectors for operation by listening to their operation sound.

Check the spark plugs whether they are wet.

Is fuel distributed to injectors?

Is fuel injected?

Is the injection quantity too much, or too little?

a. Fuel pump malfunctionIf the supply hose has a pressurized feel during cranking, the fuel system (between the fuel pumpand injectors) is normal.If it is difficult to determine whether the hose is pressurized or not, feel both the supply and returnhoses and compare the results.

b. Clogged fuel filter and fuel linec. Faulty pressure regulator

Start the engine while pinching the fuel return hose hard with fingers. If the startability of engineimproves, the pressure regulator may be faulty, rendering the fuel supply pressure too low.

d. Fault in components related to fuel pump control Faulty engine control relay Faulty wiring harness, connectors, etc. Faulty engine-ECU Faulty ignition switch

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GASOLINE ENGINE - Fuel System

ii. Injector malfunction

The engine can not start at all if none of the injectors operates. The engine will start with difficulty if oneor more injectors fail to operate. If an injector drive circuit is shorted to ground before the engine-ECU,the injector stays open and keeps injecting fuel, making it difficult for the engine to start. Faulty resistor Faulty injector Faulty injector power supply circuit wiring Faulty wiring between the injector and engine-ECU terminals Faulty ground connection of the injector power transistor (incorporated in the engine-ECU) Faulty engine-ECU

(2) Difficult to start in low temperatures

If a cold start difficulty problem occurs in a carburetor engine, everyone will almost naturally attribute it tothe choke mechanism and immediately begin checking it.In MPI engines, what is done by the choke mechanism is performed by the following two functions.

+

+

Choke system

Injector operations

Fast idle system Fuel injection boosting during warmup

Fuel injection boosting during start

i. A mixture of appropriate air-fuel ratio is not achieved during a cold start.If the fuel injection boosting function does not operate properly, a mixture rich enough for a cold start isnot achieved. The result is a difficult start.

ii. Fast idle speed, required for warm up of a cold-started engine, is not achieved.If the fast idle valve, FLICS, or the throttle valve does not open after a cold start, the engine can not runat idle stably or may stall.

(3) Difficult to restart after warmed-up

i. Vapor lock in fuel lineAfter the engine is stopped following high-speed, high-load operations, heat from the engine and theexhaust system can cause “vapor lock” in the fuel line, which makes a restart of the engine difficult.

ii. Poor residual pressure retentionA check valve is provided to retain residual pressure in the fuel line after the fuel pump has stopped forthe following reason.The ambient temperature, which is affected by the heat from the engine and other components, risestemporarily after the engine has stopped (and drops afterwards). This high ambient temperature islikely to cause vapor lock in the fuel line.As vapor lock tends to happen when residual pressure is not retained in the fuel line and the linepressure drops. To ensure easy restarting of the engine, the check valve maintains the fuel line at highpressure and prevents vapor lock at high engine temperature. Poor seating of check valve resulting in defective retention of residual pressure in fuel pump Faulty pressure regulator

iii. Fuel leakage from injectorsIf fuel is leaking from the injectors when cranking an engine that is at an operating temperature, toorich mixture renders the engine difficult to restart.

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GASOLINE ENGINE - Fuel System

2) MPI (fuel injection) control system

When the engine does not start at all or is difficult to start, most probable cases include no or inadequatesupply of electric power to the engine-ECU and/or injectors and wet spark plugs resulting from too muchinjection of fuel. Whichever the cause may be, you should first check whether the fuel pressure (fuel systempressure) is normal before inspecting the MPI control system.Faults having occurred in the control system are always stored in the diagnostic system memory and can bedisplayed in the form of codes. If any fault code is stored, be sure to perform inspection according to the code.

MPI control system

Power supply voltage (+B)

Engine speed signal Water temperature signal

(1) No or inadequate supply of electric power

The engine-ECU and injectors are supplied with electric power via the engine control relay.

If they are not supplied with adequate voltage of electric power, the engine fails to start. Faulty engine control relay Faulty engine control circuit, blown or improperly melting fuse, etc. Faulty ground circuit of the engine-ECU Faulty ignition switch circuit

(2) Faulty engine speed signal

The engine-ECU controls injection and ignition timing based on the signals it receives from the camshaftposition and crank angle sensors.If the engine-ECU is not supplied with crank angle sensor or camshaft position sensor signals, it can notcreate the injection signal.

<Reference>

With an MPI engine, the engine-ECU needs power supply voltage and engine speed signal (from the crankangle sensor or camshaft position sensor) to create the injection signal.The engine-ECU can produce the injection signal even if the intake air flow signal is faulty.If the engine-ECU does not issue the injection signal during cranking, check the following items on the unit.i. Power terminal and ground terminalii. IG terminal (V6 DOHC)iii. Injector drive terminal and power transistor drive terminal

(3) Faulty coolant temperature signal

When the output voltage of the engine coolant temperature sensor is approximately 5 V (which corre-sponds to – 45° or below) or 0 V (which corresponds to 140° or above), the engine-ECU does not usesignals from the sensor but starts processing using the preprogrammed data (which represents 80°) inorder to prevent engine from stalling or getting out of order. However, as the engine-ECU use the data nomatter how low the actual coolant temperature is, the mixture may not be rich enough for an cold engine tostart, which causes poor or difficult engine starting. This problem does not occur when restarting anengine which is at an operating temperature.

Power supply to the engine-ECU Power supply to the injectors

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GASOLINE ENGINE - Fuel System

(4) Loss of starter signal

If the ignition switch fails to send the starter signal to the engine-ECU, the injection boosting (start enrich-ment) function does not operate during engine starting. This causes poor cold engine starting perfor-mance.

(5) Checking the fuel system

i. Fuel pumpTypical causes of inoperative fuel pump Faulty fuel pump Faulty engine control relay Fault in wiring of fuel pump control circuit (open circuit, poor contact, etc.)

Battery

Dedicated fuse

Engine control relay

Engine-ECU

Ignition switch

Fuel pump test terminal

Fuel pump

<Reference>

Whether or not the fuel pump is receiving power supply volt-age can be checked easily by using the fuel pump test termi-nal. If the voltage between the fuel pump terminal and body isapproximately 8 V or above when the engine is cranking andafter the engine has started, the engine control relay contactsare closed and the pump is supplied with power of a correctvoltage.In addition to the above, the wiring between the engine con-trol relay and fuel pump and the fuel pump connectors shouldbe checked for open circuit, poor contact, and other failures.

ii. Drop in fuel supply performanceIf the fuel supply performance is deteriorated when the vehicle is climbing a slope or driving under ahigh load, the combustion pressure drops and the engine stalls.The causes of decrease in the fuel supply performance include the following:a. Insufficient fuel pump outputb. Clogged fuel filter or linec. Deformed fuel tank (that blocks the main pipe) or deformed fuel line

iii. Leaky injector (fuel drips after injection)This fault results in irregular idling operation followed by an engine stall rather than directly causing theengine to stall. While the vehicle is driving, this fault causes too rich mixture and resulting irregularoperation of the engine but does not cause a stall of the engine.When checking injectors for leakage, you must remove each injector and force fuel under pressure intoit.

iv. Faulty wiring in pump control circuitThe wiring between the engine control relay and engine-ECU (fuel pump test) terminal should bechecked for open circuit, poor contact, and other types of fault.

v. Faulty engine-ECUEnsure that all of the following conditions are satisfactory before proceeding to inspection of the en-gine-ECU.a. The pump rotates while the engine is being cranked.b. The engine-ECU is receiving signals from the crank angle (or camshaft position) sensor.c. With the ignition switch in the ON position, the pump rotates when the engine control relay’s fuel

pump relay coil is directly shorted to the ground.

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GASOLINE ENGINE - Fuel System

(6) Checking the fuel system

i. Injector problemsIf the fuel injection quantity (and thus the air-fuel ratio) is different between cylinders, the engine speedcan become unstable. Uneven fuel injection may results from both electrical causes and mechanicalcauses (such as a sticky nozzle needle and leaky injector or after-injection fuel drips).a. Idling operation of the engine will be unstable and irregular if any injector does not operate at all or

operates improperly due to an open injector or resistor circuit or other electrical problems. If such aproblems is present, the engine does not run normally even when the engine speed is increased.

b. Defective idling operation can also result from a significant difference in injection quantity betweencylinders due to a mechanical fault in an injector. If such a problem is present, the engine does notrun normally even when the engine speed is increased.To check for uneven injection between cylinders, the injectors need to be removed from the intakemanifold. Therefore, this check should be undertaken after the other checks have been carried out.Check also the direction and pattern of fuel splays.

c. If the needle valve does not seat properly and fuel leaks from the nozzle, the engine speed canbecome unstable and also after-fire can occur during deceleration when supply of fuel is limited.

ii. Fuel pressure problemsIf the pressure of the fuel fed to the injectors is not high enough for correct injection, the quantity of thefuel injected will be insufficient even if the injection time is correctly regulated by the engine-ECU. As aresult, the mixture becomes too lean, causing the idle speed to be too low or unstable. A simplemethod of checking the fuel pressure is to disconnect the vacuum hose from the pressure regulator orpinch the return hose with fingers and check any change in the idle speed. For precise inspection, usea fuel pressure gauge for the check.Possible causes of fuel pressure problems include the following:a. Faulty fuel pumpb. Faulty pressure regulator

With a fuel pressure gauge connected, pinch the return hose with fingers. If the needle of the gaugeindicates a higher pressure, the pressure regulator is faulty.

c. Clogged fuel filter or piping

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GASOLINE ENGINE - Fuel System

3. Fuel Pump Operation Check1) Cause the fuel pump to operate using the MUT-II and make

sure it certainly operates.2) If the fuel pump does not operate, perform the following

test. If the result is satisfactory, then inspect the fuel pumpdrive circuit.(1) Turn off the ignition switch.(2) Apply battery voltage directly to the No. 2 terminal of

the fuel pump test connector (black) and check whetherthe pump operates by listening to the sound it will gen-erate.

NOTERemove the fuel filler cap and listen to the pump operat-ing sound through the filler port since the pump is of an in-tank type and the sound would otherwise be difficult tolisten.

(3) Pinch the fuel hose lightly between fingers to checkpresence of fuel pressure.

3) Perform the following inspection to check the delivery rateof the fuel pump.(1) Procedure

i. Remove the return hose from the pressure regula-tor.

ii. Connect one end of a hose to the pressure regula-tor and put the other end in a container.

iii. Measure the quantity of fuel delivered by the pumpin a given period of time.

yreviledleuF epyT enignE

08 , h/ IPM 37G6,21A6,9G4,6G4,1G4

IDG 29G4

001 , h/ IPM 4D47G6,)ESPILCE(36G4

IDG 7G6,39G4,46G4

(2) Possible causes of insufficient delivery ratei. Fault in the fuel pumpii. Clogged fuel filteriii. Clogged fuel pipeiv. Fault in pressure regulator

Fuel pump testconnector

Pressureregulator

Checking fuel pump delivery rate

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GASOLINE ENGINE - Fuel System

4. Fuel Pressure Check1) Relieving residual pressure before start of check

The high-pressure (fuel feed) line of the fuel system always remains under pressure even after the enginestopped. If the pressure is not relieved before removing a hose or other system components, a dangerouscondition may result from high pressure fuel forced out of the line. Relieve the fuel pressure according to thefollowing procedure and also cover the area around the hose or component to be removed in order to mini-mize spillage.

(1) Disconnect the fuel pump connector.(2) Start the engine. Run the engine until it stalls, then turn off the ignition switch.(3) Remove a hose or other necessary components taking care not to allow fuel (that may come out of the

system even after pressure has been relieved) to come into contact with sparks or high temperaturecomponents.

2) Measuring fuel pressure

(1) Relieve the residual pressure in the fuel pipe lines to pre-vent fuel from gushing out.

(2) Disconnect the high-pressure fuel hose from the deliverypipe.

CautionPrevent splashing of fuel which may be forced out byremaining pressure in the fuel pipe line by coveringconnection of the pipe and hose with a shop towel orother cloth.

(3) Change the adapter of the fuel pressure measurementspecial tool.

(4) Set up the fuel pressure measurement special tool.

<When MUT-II is used>

i. Install the fuel pressure measurement special tool be-tween the delivery pipe and high-pressure fuel hose.

ii. Install the fuel pressure gauge set (special tool) on thefuel pressure measurement special tool with a gasketin between.

iii. Connect the leads of the fuel pressure gauge set tothe power supply (cigarette lighter socket) and the MUT-II.

<When MUT-II is not used>

i. Install a fuel pressure gauge on the fuel pressure mea-surement tool with an appropriate O-ring or gasket inbetween.

ii. Install the gauge and special tool assembled in step i.above between the delivery pipe and high-pressurefuel hose.

High-pressure fuel hose

MB991637

Gasket

MD998709

MD998742

Delivery pipe 1FU1197

High-pressure fuel hose

Delivery pipe

Fuel pressure gauge

O-ring or gasket

MD998709

MD998742

1FU1198

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GASOLINE ENGINE - Fuel System

(5) Connect with a jumper wire the battery positive (+) termi-nal to the No. 2 terminal (fuel pump drive terminal) of thethree-pin fuel pump test connector shown to the left tooperate the fuel pump. With the fuel system under pres-sure, make sure there is no leakage anywhere in the sys-tem.

(6) Disconnect the jumper wire from the fuel pump test con-nector to stop the fuel pump.

(7) Start the engine and let it run at idle.(8) With the engine idling, measure the fuel pressure.

Standard value:Non-turbocharged engine

Approx. 265 kPa 2.7 kgf/cm2

Turbocharged engine (Lancer Evolution)Approx. 230 kPa 2.35 kgf/cm2

(9) Disconnect the vacuum hose from the fuel pressure regu-lator, then measure the fuel pressure while closing thedisconnected end of the hose with a finger.

Standard value:Non-turbocharged engine

324 – 343 kPa 3.3 – 3.5 kgf/cm2

Turbocharged engine289 – 309 kPa 2.95 – 3.15 kgf/cm2

(10)Race the engine a few times, then make sure a fuel pres-sure of the idling operation level is still maintained.

(11)While repeating engine racing, lightly pinch the fuel re-turn hose between fingers to make sure the fuel flowing inthe hose is under pressure.

NOTEIf the fuel flow rate is insufficient, there is no pressure be-ing felt in the return hose.

6AF0324

(12)If the measurement value is not as specified, determine the cause according to the following table andtake appropriate remedial actions.

motpmyS esuacelbaborP ydemeR

.wolootsierusserpleuF enigneretfasporderusserpleuF

.gnicar nigniwolfleufnierusserpoN

.esohnruter

retlifleufdeggolC .retlifleufecalpeR

leufnievlavfognitaesrooPleuffoegakaelrorotalugererusserp

gnirpskaewoteudenilnruterotni

.rotalugererusserpleufecalpeR

yreviledpmupleufwolooT.erusserp

.pmupleufecalpeR

.hgihootsierusserpleuF erusserpleufnievlavykcitSrotaluger

.rotalugererusserpleufecalpeR

ro/dnaesohnruterleufdeggolCepip

.epipro/dnaesohecalperronaelC

tnereffidtonsierusserpleuFsiesohmuucavnehwneewteb

sitinehwdnadetcennoc.detcennocsid

deggolcroesohmuucavnekorBgnittif

naelcroesohmuucavecalpeR.gnittif

rotalugererusserpleufnitluaF rotalugererusserpleufecalpeR

6AF0289

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GASOLINE ENGINE - Fuel System

(13)Stop the engine and check the change in the fuel pressure gauge reading. All the system components arenormal if the reading does not drop within two minutes. If it does, observe the gauge to see how fast thepressure drops, then find the cause according to the following table and take appropriate remedial actions.

motpmyS esuacelbissoP ydemeR

retfaylwolssporderusserpleuF.nwodtuhsenigne

)s(rotcejnimorfegakaeL .naelcro)s(rotcejniecalpeR

leuffotaesevlavhguorhtegakaeLrotalugererusserp

.rotalugererusserpleufecalpeR

ylkciuqsporderusserpleuF.nwodtuhsenigneretfayletaidemmi

otgniliafpmupleufnievlavkcehCesolc

.pmupleufecalpeR

(14)Relieve the residual pressure in the fuel pipe line.(15)Remove the special tool from the delivery pipe.

CautionPrevent splashing of fuel which may be forced out by remaining pressure in the fuel pipe line bycovering connection of the pipe and special tool with a shop towel or other cloth.

(16)Replace the O-ring at the end of the high-pressure fuel hose. Apply thin coat of engine oil to the new O-ring before installation.

(17)Install the high-pressure fuel hose into the delivery pipe, then tighten the mounting bolts to the specifiedtorque.

Tightening torque: 12 ± 1 Nm

(18)Check the fuel line for leakage as follows:i. Apply battery voltage the fuel pump drive terminal of the fuel pump test connector to operate the fuel

pump.ii. With the fuel line under pressure, check it for leakage.

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GASOLINE ENGINE - Fuel System

5. Injection Spray Check(1) Relieve the fuel pipe line residual pressure to prevent fuel from being forced out.(2) Remove the injector.(3) Set up the special tools (injector test set, adapter, fuel pressure regulator, and clip) as shown.

Main hose MD998741

MD998706

7FU0145

Fuel pressure regulator:MD116395

Return hose

ClipMB991608 or (MB991692: Only for 6G7 SOHC)

InjectorBattery

MB991607

(4) Apply battery voltage to the No. 2 terminal (fuel pump driveterminal) of the fuel pump test connector to operate thefuel pump.

(5) Energize the injector to check the fuel spray condition. Thespray condition may be judged good unless the spray pat-tern appears extremely improper.

(6) Stop energizing the injector and check it for leakage fromthe end of the nozzle.

Standard value: 1 drop or less per minute

(7) Without operating the fuel pump, energize the injector tokeep it open until fuel spray stops, then disconnect thespecial tools to restore the original state.

01R0546

Main hose Return hose

Injector

Battery

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GASOLINE ENGINE - Fuel System

6. Fuel Pressure Check of GDI Engine1) Measurement of fuel high pressure between fuel

pump (high pressure) and injectors

NOTEMeasurement of the fuel pressure between the fuel pump (highpressure) and the injectors should be carried out after check-ing that the fuel pressure between the fuel pump (low pres-sure) and the fuel pump (high pressure) is normal.

(1) Connect the MUT-II to the diagnosis connector.(2) Disconnect the injector intermediate harness connector

in order to stop the injector operation.

(3) Turn the ignition switch to ON.(4) Select “Item No. 74 ” (fuel pressure sensor) from the MUT-II Data list.(5) Crank the engine continuously for 2 seconds or more, and visually check that there are no fuel leaks from

any parts.

CautionIf any fuel leaks appear, stop cranking immediately and repair the source of the leak.

(6) Check if the fuel pressure is more than 1 MPa immediately after 20 seconds have passed since crankingwas finished.

(7) If the fuel pressure is lower than 1 MPa, it means that there is likely to be a leak in the high-pressure fuelsystem, so this system should be checked.

(8) Turn the ignition switch to OFF.(9) Connect the injector intermediate harness connector.(10)Start the engine and run at idle.(11)Measure fuel pressure while the engine is running at idle.

Standard value: 4 – 7.5 MPa

(12)Check that fuel pressure at idle does not drop even after the engine has been raced several times.(13)If fuel pressure is out of the standard value, troubleshoot and repair according to the table below.

motpmyS esuacelbaborP ydemeR

wolooterusserpleuF gnicarretfasporderusserpleuF

oteudedisnruterotgnikaelleuFhgih(rotalugererusserpleufroopdelttesfognitaesevlav)erusserp

gnirps

rotalugererusserpleufecalpeR)erusserphgih(

)erusserphgih(pmupleufwoLerusserpyreviled

pmupleufehtecalpeR)erusserphgih(

hgihooterusserpleuF erusserpleufnievlavgnidniB)erusserphgih(rotaluger

rotalugererusserpleufecalpeR)erusserphgih(

epiproesohnruterleufdeggolC epiproesohecalperronaelC

(14)Stop the engine and turn the ignition switch to OFF.(15)Disconnect the MUT-II.

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GASOLINE ENGINE - Fuel System

2) Fuel leak check

(1) Connect the MUT-II to the diagnosis connector.(2) Disconnect the injector intermediate harness connector.(3) Turn the ignition switch to ON.(4) Select “Item No. 74 ” from the MUT-II Data list.(5) Crank the engine continuously for 2 seconds or more, and

visually check that there are no fuel leaks from any parts.

CautionIf any fuel leaks appear, stop cranking immediatelyand repair the source of the leak.

(6) Crank the engine, and then measure fuel pressure imme-diately after 20 seconds.

Limit: Minimum 1 MPa

CautionIf the fuel pressure is less than 1 MPa, there may be apartial fuel leak in the high-pressure fuel system.

(7) Turn off the ignition switch.(8) Reconnect the injector intermediate connector.(9) Remove the MUT-II.

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3) Fuel pump connector disconnection (how to reducefuel pressure)

When removing the fuel pipe, hose, etc., since fuel pressurein the fuel pipe line is high, do the following operation so as torelease fuel pressure in the line and prevent fuel from runningout.(1) Remove the fuel filler cap to release pressure in the fuel

tank.(2) Remove the fuel pump relay.(3) Connect the MUT-II to the diagnosis connector.

CautionTurn off the ignition switch before disconnecting orconnecting the MUT-II.

(4) Turn off the ignition switch.(5) Select “Item No. 74” from the MUT-II Data list.(6) Crank the engine for at least two seconds.(7) If the engine is not be started, use the MUT-II to make

sure that the fuel-pressure is 0.5 MPa or less. Then turnoff the ignition switch.

(8) If the engine is started, release fuel pressure by the fol-lowing procedure:i. Turn off the ignition switch, and then stop the engine.ii. Disconnect one of the ignition coil connectors.iii. Crank the engine for at least two seconds.iv. Use the MUT-II to make sure that the fuel pressure is

0.5 MPa or less. Then turn off the ignition switch.v. Reconnect the ignition coil connector.

CautionClean the spark plug which corresponds to the dis-connected ignition coil connector.

(9) Remove the MUT-II.(10)Install the fuel pump relay.

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GASOLINE ENGINE - Intake System

INTAKE SYSTEM

1. Intake System Service1) Major intake system problems

The intake system consists of main air passage components (air cleaner, air flow sensor, throttle valve, surgetank, intake manifold, etc.), bypass air passage components (idle adjusting screw, idle speed control valve(ISC), etc.), and emission control devices (exhaust gas recirculation (EGR) valve etc.).The problems that may occur with the intake system are the following three problems.

(1) Poor output characteristics of the air flow sensor

If this problem occurs, the engine-ECU issues injector drive signals based on erroneous air flow signalsthat do not represent actual intake air flow conditions.

(2) Outside air into the system at a point downstream of the air flow sensor

Since air of an amount more than that detected by the air flow sensor enters the engine, the actual mixturebecomes leaner than the air-fuel ratio determined by the engine-ECU.

(3) Improper opening of the bypass air passage

If the opening of the bypass air passage is improper, such problems will occur as poor cold start perfor-mance and poor fast idling and unstable idling performance. Effects of this fault will decrease as thethrottle valve opens wider since the bypass air passage is much narrower than the main air passage.

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2) Inspection of air-fuel ratio

When the engine is malfunctioning and the symptom suggests an improper air-fuel ratio, the following meth-ods can be used to determine whether the mixture is too rich or too lean.

(1) Secondary air method

With the engine running, disconnect one of the hoses connected to the surge tank to let air be drawn. Ifengine operation becomes regular, the malfunction is caused by too rich mixture. With vehicles equippedwith 4G1 series engines, however, this method can not be used to judge the air-fuel ratio as the vacuumsensor used in them makes disconnection of the hose cause only an increase in the engine speed.

(2) Oxygen sensor output method (MPI/GDI engine with oxygen sensor)

Let the engine warm up until the operating temperature of oxygen sensor, then measure the output volt-age of the sensor. If the voltage is closer to 1 V, the mixture is judged to be too rich and if it is closer to 0 V,the mixture is judged to be too lean.

(3) Carbon monoxide (CO) concentration method

Measure the CO concentration in exhaust gases using CO meter. If almost no CO is detected, the mixtureis leaner than the stoichiometry.

(4) Choke valve method (engine with carburettor)

If idling operation of the engine is irregular, improper choke valve opening is suspectable as a cause. Moveby hand the choke valve slowly from the open to close positions and vice versa. If a regular engine opera-tion is restored when the valve is moved a little beyond the half-open position, the mixture can be judgedto be too rich.

3) Inspection of intake air flow restricting factors

(1) Clogging of air filter

Visually check the air filter for clogging.

(2) Flattened hoses

With the engine running, quickly open the throttle valve to make sure the intake air hose or other intakesystem hoses are not flattened.

4) Inspection of exhaust gas flow restricting factors

If the muffler and/or catalytic converter is blocked by deposits, increased exhaust resistance prevents thecombustion chambers from being sucked sufficient amount of mixture. This results in poor engine output.

<Reference>

Inspection of exhaust system for clogging(1) If the exhaust system is clogged anywhere, the maximum engine speed drops when the accelerator pedal

is depressed fully with the vehicle running in the first or second gear.Remember the same result may be caused also by inadequate fuel supply.

(2) The exhaust system is seens to be clogged if an engine operating at a speed of approximately 2000 r/min,and the vacuum gauge indicates a pressure higher than when it is running at idle.

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GASOLINE ENGINE - Intake System

Intake system・ Outside air into system・ Air valve

Fuel system

MPI control system・ System with air flow sensor・ System with vacuum sensor

Idle speed control system

5) Inspection of intake system

(1) Outside air into the system

i. System with an air flow sensor (AFS)If outside air into the intake system at a point downstream of the AFS, the frequency of the AFS outputsignal sent to the engine-ECU is lower than that corresponding to the amount of the air the engine isactually drawing, so the quantity of injected fuel becomes smaller than the really required quantity. Asa result, too lean mixture slows down the idling speed and makes engine operation irregular.However, if the air leakage is small in amount, the idle speed control (ISC) servo system operates tocompensate for loss of idling speed, which makes it difficult to determine whether it is causing idlingproblem or not.Outside air leakage into the intake system typically occurs from the following causes: Fault in positive crankcase ventilation (PCV) valve Loosely connected or disconnected intake system hoses and other components Broken injector insulator(s) Broken gaskets and other seal parts

ii. System with a vacuum sensorIf outside air into the intake system at a point downstream of the throttle valve, the idle speed in-creases. If the amount of leakage is large, supply of fuel may be limited, possibly resulting in hunting.

Surge tank Vacuum sensor

Engine-ECU

(Quantity of fuel increased)

Idling speed increases

(Excess air increases)

Output voltage rises momentarily (then lowers)

(Outside air into intake system)

(2) Problems in throttle body related parts

i. Blocked bypass air passageDuring idling operation of the engine, the throttle valve is in the fully closed position, disabling theengine from being supplied with adequate amount of air if the bypass air passage is blocked, so theengine is very likely to stall. If the idling speed does not increase even if the speed adjusting screw(SAS) is fully turned out during adjustment of the basic idling speed adjustment, the cause may be ablocked bypass air passage.

ii. Carbon or other deposits on throttle valveIf there are carbon or other deposits on the throttle valve, the idling speed becomes lower than normal.Also, the idling speed varies as the amount of deposits changes. On the other hand, deposits mayinterfere with free movement of the valve. If they prevent the valve from returning to the fully closedposition, excessively introduced air will cause an abnormally high idle speed.

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(3) Faulty operation of fast idle air valve

If the opening and closing operation of the fast idle air valve is improper, the fast idle speed during warm upmay be too high or the engine speed may fail to return to the standard idle speed even after the engine hasbeen warmed up to the operating temperature.i. Improper closing operation

If the closing movement of the valve is interfered by jamming of foreign matters or other causes, largeamount of air continues being supplied even after engine warm up, resulting in excessively high idlespeed.The fast idle air valve is installed directly on the throttle body. Make sure the fast idle speed decreasesas the engine coolant temperature rises. If the engine speed fails to decrease, it is necessary to checkwhether the engine slows down when the air inlet port of the throttle body is closed by a finger.

ii. Improper opening operationIf the fast idle air valve does not open smoothly, the fast idle speed does not rise sufficiently andfluctuates during warm up after cold-starting the engine. The engine may stall before its temperaturebecomes high enough for normal operation.

(4) Improperly adjusted speed adjusting screw (SAS)

If the SAS is largely out of adjustment, an inappropriate amount of air supplied during idling causesunstable idle speed of the engine.

<Reference>

(1) Function of ISC servo systemWhen the engine is operating at low speeds, larger part of the intake air flows through the bypass airpassage than the remaining part which flows through the main air passage. Under this condition, the ISCservo system can change the engine speed by changing the amount of air flowing through the bypass airpassage.When the engine is increasing its speed and thus requires a larger amount of air, almost all the intake airflows through the main air passage and only small part of the air flows through the bypass air passage.The ISC servo system then can not have control over the engine speed any more.

(2) Idling speed control after stop of feedback control due to fault of oxygen sensor or other sensorsi. If a sensor becomes faulty, the mixture is always maintained at around the stoichiometric air-fuel ratio,

so that the idling speed does not change.ii. If the feedback control is stopped due to outside air leakage into the system at a point downstream of

the air flow sensor, the idling speed is likely to drop or fluctuate since the mixture may become too leanor too rich.

6) Errors in intake air flow and manifold vacuum signals

(1) Erroneous signals from air flow sensor

If the air flow sensor issues a signal of a frequency lower than the frequency that correctly reflects theactual amount of the intake air (that is, if the sensor sends a signal erroneously indicating “too small airamount” to the engine-ECU), the injected fuel is not enough for the actual amount of air, resulting in pooroutput of the engine. This error does not cause a diagnosis trouble code to be generated.

(2) Erroneous signals from vacuum sensor

If the vacuum sensor sends to the engine-ECU a signal not reflecting the actual flow of air, excessivelylarge or small amount of fuel is injected, causing deviation from the appropriate air-fuel ratio for the engineoperating condition at that time. In this case, the engine speed become unstable or the engine fails to revup.i. When the cause is an internal fault of the sensor

An erroneous signal indicating an air amount smaller than the actual amount is sent to the engine-ECU.

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ii. When the cause is clogging in the sensorIf the vacuum sensor or the vacuum hose connected to the sensor is clogged with something like dust,the output voltage of the sensor always represents the intake manifold vacuum pressure at the pointimmediately before the clogged section. The vacuum pressure may, therefore, cause the mixture to beeither too lean or too rich with resulting unstable engine speed. A variety of symptoms may result froma vacuum sensor/pipe clogging problem, such as failure to rev up, irregular idling operation in spite ofnormal operation in high-speed range, etc.

<Reference>

Erroneous vacuum sensor output signals(1) If the sensor always outputs a signal of idling level

The engine operates normally when it runs at idle. If the throttle valve is opened quickly, the engine willstall. If it is opened slowly, the engine speed increases accordingly.

(2) If the sensor always outputs a signal of atmospheric pressure levelAfter start, the engine will soon stall without being able to maintain the idle speed. If the engine is startedwith the throttle wide open, it operates irregularly and emits black smoke.

<Reference>

(1) Backup functionIf a fault occurs in the engine-ECU or the vacuum sensor issues erroneous manifold absolute pressuresignals, the amount of injected fuel would become too much or too little for the amount of intake air,causing the engine to stall. The backup function refers to a capability which, when the engine-ECU or thesensor fails, enables a backup mode program to be used to keep the vehicle operational safely. The driveris notified of activation of the function by illumination of the engine warning lamp.

(2) Vacuum sensorThe vacuum sensor detects the amount of intake air flowin terms of the intake manifold absolute pressure. A sili-con chip in the sensor generates voltage signal propor-tional to the difference in pressure between the vacuum inthe chamber formed in the sensor and the negative pres-sure caused in the manifold by the flow of air. The outputsignal is sent to the engine-ECU.Vacuum sensor output voltage can be compared to read-ings on a circuit tester which is used to measure the amountof intake air flow.i. The engine-ECU makes the injection time shorter when

the vacuum sensor output voltage becomes lower.ii. The engine-ECU makes the injection time longer when

the vacuum sensor output voltage becomes higher.iii. The injection time becomes longer if the vacuum hose

of the vacuum sensor is disconnected as the back-upfunction.

Pressure (kPa mmHg)

Out

put

vol

tag

e (V

)

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GASOLINE ENGINE - Intake System

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7) Inspection of idle speed control (ISC) system

(1) Fault conditions resulting from malfunction of ISC servoISC servo using stepper motor or DC motorThe engine-ECU causes the stepper motor or DC motor to move by the amount it has determined basedon signals from the relevant sensors to control the idle speed in accordance with loads on the engine.The opening of the ISC servo of this type depends only on the signal from the water temperature sensorwhen the engine has been stopped and then restarted. If a fault occurs when the ISC servo is in a wideopen position, the servo remains in this position, causing the engine to idle at too high a speed when it isrestarted. If a fault occurs when the servo is opened to an idle position and the engine is still cold, theservo remains in that position when the engine is then restarted. As the engine can not operate at a fastidle speed, it will operate only at an abnormally low idle speed irregularly and may sometimes stall. De-pending on opening of the servo when a fault occurs, therefore, subsequent engine operation will differ.Malfunction of an ISC servo of this type may typically result from the following causes: Failure in ISC servo Open circuit, poor connector contact, or other defect in the wiring between control relay and ISC servo

power supply terminal Open circuit, poor connector contact or other defect in the wiring from ISC servo to engine-ECU

(2) Fault conditions resulting from improperly adjusted speed adjusting screw

With an engine whose ISC servo uses a stepper motor, it is essential to check the speed adjusting screwon the throttle body for proper adjustment by measuring the basic idle speed. If the speed adjusting screwis loosened excessively, the ISC servo can not have control over the idle speed.

<Reference>

(1) Operation test of stepper motorWarm up the engine, then install a tachometer on it.After making sure the engine speed is within the standardidle speed range, screw the speed adjusting screw on thethrottle body outward until the engine speed becomes 800r/min. Check whether the engine speed returns to the origi-nal speed a short time later. If the original speed is re-sumed normally, then screw the speed adjusting screwinward until the engine slows down to a speed between550 and 600 r/min and make sure the engine returns to astandard idle speed within a short time.

(2) Fault in stator coils in stepper motorThe engine-ECU drives the stepper motor by groundinginside itself one of the four stator coil leads appropriately.If open circuit occurs in one or two of these four circuits, itis theoretically possible for the ISC servo to control theidle speed, but satisfactory control is actually impossiblefor an ISC servo in such a condition.

Battery

Fusible link

Engine control relay

ISC servo

ECU

Page 49: Troubleshooting Engines

44

Pub. No. PTEE0113

GASOLINE ENGINE - Intake System

2. Cleaning Valve and Surrounding Area in Throttle Body(1) Start the engine and let it warm up. When the coolant tem-

perature has risen above 80°C, stop the engine.(2) Disconnect the air intake hose from the throttle body.(3) Plug the bypass passage inlet port in the throttle body.

CautionMake sure the plug seals the port completely to pre-vent any entry of wash solution into the bypass pas-sage.

(4) Spray cleaning solvent over the valve through the throttlebody inlet port and leave it for 5 minutes.

Cleaning solventMZ100138 (Japan Bars Quick Engine Tuner)MZ100139 (Threebond 6601)

(5) Start the engine, race it a few times, then run it at idle forabout 5 minutes.

NOTEThe engine may idle unstably or, in the worst case, it maystall since the bypass passage is closed by the plug. If thisoccurs, open the throttle valve slightly.

(6) Repeat steps (4) and (5) if necessary to remove depositson and around the throttle valve completely.

(7) Remove the plug from the bypass passage inlet port.(8) Connect the air intake hose.(9) Use the MUT-II to erase the diagnosis code.(10)Adjust the basic idle speed.

NOTEIf the engine hunts during idling after the basic idle speedadjustment, disconnect the battery negative cable and waitmore than 10 seconds before reconnecting it, then oper-ate the engine at idle for about 10 minutes.

Operating Sound Check

(1) Make sure the engine coolant temperature is lower than20°C.

NOTEIf the coolant temperature is higher than 20°C, you maydisconnect the water temperature sensor connector andconnect a water temperature sensor whose temperatureis lower than 20°C to the harness side connector.

(2) Turn the ignition switch to the ON position (without start-ing the engine), then listen to the sound that indicates op-eration of the stepper motor in the ISC servo.

(3) If there is no sound generated, check the stepper motordrive circuit. If the circuit is found normal, the stepper mo-tor itself or the engine engine-ECU is probably faulty.

3. Inspection of ISC Servo

6AF0339

ISC servo(stepper motor)

Bypass passage

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45

Pub. No. PTEE0113

GASOLINE ENGINE - Intake System

4. Adjustment of Basic Idle SpeedNOTE This adjustment is usually unnecessary as the speed adjusting screw (SAS) has been set for the

correct basic idle speed at the factory. Perform the basic idle speed adjustment in accordance with the following instructions if the SAS set-

ting is inadvertently disturbed, the idle speed is far higher than the standard speed, or the idle speeddrops when the air conditioner or other loads are applied.

Perform the adjustment after making sure the spark plugs, injectors, ISC servo, and compressionpressure are all normal.

(1) Set the vehicle into the pre-inspection conditions.(2) Connect the MUT-II to the diagnosis connector.(3) Start the engine and let it run at idle.(4) Select Item No. 30 of the actuator test menu on the MUT-II.

NOTEThis locks the ISC servo in the basic step which is provided for adjustment of the basic idle speed.

(5) Check the basic idle speed.

Basic idle speed

Standard value <GDI>:

smetI )mpr(deepseldI ledomelciheV

39G4 )T/M(noissimsnartlaunaM 006 ± 008–05 ± *05 AMSIRAC

)T/A(noissimsnartcitamotuA 056 ± **mpr05

46G4 noissimsnartlaunaM 006 ± **mpr001 NOGAWECAPS

noissimsnartcitamotuA 056 ± **mpr001

47G6 noissimsnartlaunaM 006 ± ***mpr001 OREJAP

noissimsnartcitamotuA

NOTE*: The idle speed in vehicles with manual transmission varies as shown in the table above in accordance with

the transmission oil temperature. (4G93)**: After 4 minutes or more have passed in the idle running condition, the idle speed will become 750 rpm.

(4G93), 700 rpm (4G64)***: After 4 minutes or more have passed in the idle running condition, the idle speed will become 700 ± 100 rpm

(6G74)

Standard value <MPI>:

enignE )mpr(deepseldI ledomelciheV

1G4 057 ± 05 RECNAL

6G4)T/M(9G4)T/A(9G4

057 ± 001057 ± 05008 ± 05

TNARAG

1A6 056 ± 001

7G6 007 ± 001 OREJAP

NOTE When the vehicle is new (up to about 500 km), the idle speed may be 20 to 100 r/min lower than the

standard. Deviation of this order does not require any adjustment. If the engine stalls or the idle speed is too low with the engine on the vehicle that has traveled enough

distance (longer than about 500 km) for stabilized idle speed, the cause may be deposits on andaround the throttle valve. Perform the throttle valve cleaning procedure.

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GASOLINE ENGINE - Intake System

5. Emission Control SystemsAmong the emission control systems, the one that can cause engine stalls is the exhaust gas recirculation(EGR) system. The engine will stall if the EGR system allows exhaust gas to flow into the intake manifoldduring idling.EGR system related engine stalls occur more often by the EGR valve failing to return (close) after normalopening due to sticking of the valve itself than by false operation of the EGR system during idling. Wheninspecting the EGR system, therefore, the valve must be checked for smooth movement and complete clo-sure.Dealing with complaints related to the emission control systems is rather difficult; the problem can be solvedby performing repair if a system is found malfunctioning, but you will have a job finding causes if all theemission systems are properly functioning.The inspection step you should take when dealing with a emission control system problem is to test drive thevehicle with the suspect emission control system stopped to determine whether it is really the cause or not.

1) Inspection of EGR system

Under what condition should this inspection be performed?The EGR system should be inspected when the driveability deteriorates.

Why does the problem occur?The cause may be the EGR valve sticking in the open position.

2) Inspection of positive crankcase ventilation (PCV) system

Under what condition should this inspection be performed?The PCV system should be inspected when the emission level is high, idling operation is irregular, engineoil is contaminated, rust of engine internal components, or air cleaner is contaminated.

Why do the problems occur?The problems result from leakage of blow-by gas due to cracks and other damage in rubber hoses andmalfunction of the PCV valve.

3) Inspection of evaporative emission control system

Under what condition should this inspection be performed?The evaporative emission control system should be inspected when any of the following problem occurs.• The fuel tank has deformed.• The carburetor or injectors have a shortage of fuel supply.• Engine idling operation gets out of order due to fuel vapor entering the intake manifold.• The engine is difficult to start due to too rich mixture.

Why do the problems occur?The problems occur when the two-way valve, canister, vapor line, purge control valve and/or fuel filler capare faulty.

(6) If the basic idle speed is out of specification, adjust it byturning the SAS.

NOTEIf the idle speed is higher than the standard speed evenwhen the SAS is fully screwed in, check if there is anymark indicating disturbance of fixed SAS setting. If thereis a one, then adjust the fixed SAS.

(7) Press the clear key to cancel the actuator test function.

NOTEIf no clear key has been pressed, the forced activation willlast for 27 minutes.

(8) Turn the ignition switch to the OFF position.(9) Restart the engine and let it run at idle for about 10 min-

utes to make sure all idling conditions are good.

6AF0337

Page 52: Troubleshooting Engines

Diesel Engine

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DIESEL ENGINE - Diesel Engine Troubleshooting

DIESEL ENGINE TROUBLESHOOTINGThe two factors that are essential for a diesel engine to operate properly are creating an “appropriate com-pression pressure” for which the engine’s basic mechanisms are responsible and achieving “fuel injection incorrect spray condition and timing” for which the fuel system is responsible.

Appropriate compression pressure Fuel injection in correct spray and timing

Appropriate compression

pressure

E1225

Correct injection

timingCorrect spray

E1226

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DIESEL ENGINE - Engine Basic Mechanisms

1. Compression Pressure Inspection (4D56)1) Perform inspection and adjustment with the vehicle in the

following condition. Engine coolant temperature: 80 – 95°C (176 – 203°F) Lights and all accessories: OFF Transmission: Neutral (P range for vehicle with an au-

tomatic transmission)2) Remove all of the glow plugs.

CautionBe careful not to subject the glow plugs to any shock.

3) Disconnect the fuel cut solenoid valve connector.

NOTEDoing this will stop carrying out fuel injection.

4) Cover the glow plug holes with a rag etc., and after theengine has been cranked, check that no foreign materialis adhering to the rag.

Caution Keep away from the glow plug holes when crank-

ing. If compression is measured while water, oil, fuel,

etc., that has come from cracks is inside the cylin-der, these materials will become heated and willgush out from the glow plug hole, which is dan-gerous.

5) Set the compression gauge to one of the glow plug holes.6) Crank the engine and measure the compression pressure.

Standard value:2650 kPa (27.0 kg/cm2, 384 psi.)<Vehicles with oil cooled turbocharger>3040 kPa (31.0 kg/cm2, 441 psi.)<Vehicles with water cooled turbocharger>

Limit:1880 kPa (19.2 kg/cm2, 273 psi.)<Vehicles with oil cooled turbocharger>2200 kPa (22.4 kg/cm2, 319 psi.)<Vehicles with water cooled turbocharger>

7) Measure the compression for all the cylinders, and checkthat the pressure differences of the cylinders are belowthe limit.

Limit: 290 kPa (3.0 kg/cm2, 43 psi.)

8) If there is a cylinder with compression or a compressiondifference that is outside the limit, pour a small amount ofengine oil through the glow plug hole, and repeat the op-erations in steps 6) and 7).i. If the compression increases after oil is added, the

cause of the malfunction is a worn or damaged pistonring and/or cylinder inner surface.

ii. If the compression does not rise after oil is added, thecause is a burnt or defective valve or pressure is leak-ing from the gasket.

9) Connect the fuel cut solenoid valve connector.10)Install the glow plugs.

ENGINE BASIC MECHANISMS

Compressiongauge

01W532

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Pub. No. PTEE0113

DIESEL ENGINE - Engine Basic Mechanisms

1) 4D56 engine

(1) Turn the crankshaft clockwise and align the timing markon camshaft sprocket with its mating mark.

2. Valve Clearance Adjustment

(2) Adjust the valve clearance at points shown in the illustra-tion.

(3) Loosen the adjusting screw lock nut.(4) Using a thickness gauge, adjust the valve clearance by

turning the adjusting screw.

Standard value: 0.15 mm (on cold engine)

(5) While holding the adjusting screw with a screwdriver,tighten the lock nut.

NOTEIf the elephant foot type adjusting screw is provided, in-sertion of a thickness gauge may be hindered by theslanted pad when rechecking the clearance after adjust-ment. To avoid this, insert a thickness gauge in the direc-tion from the center line of the cylinder head to outside.

(6) Rotate clockwise the crankshaft one complete turn (360degree).

(7) Adjust the valve clearance at points shown in the illustra-tion.

(8) Repeat steps (3) to (5) to adjust the valve clearance ofremaining valves.

NOTEWith the engine mounted on vehicle, warm up to the en-gine. Then, check for valve clearance at hot engine andadjust if necessary.

Standard value: 0.25 mm (on hot engine)

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DIESEL ENGINE - Engine Basic Mechanisms

2) 4M40 engine

(1) Warm up the engine to 80 – 95°C in the coolant temperature. Stop the engine.(2) Remove the rocker cover.(3) Remove all the glow plug plate and glow plugs.(4) Turn the crankshaft pulley until the notch on it is aligned with the timing mark “0” to bring the piston in the

No. 1 or No. 4 cylinder to the top dead center of its compression stroke.

Lifter Shim Installation

: When No. 1 cylinder is at compression top dead centerposition.

: When No. 4 cylinder is at compression top dead centerposition.

Standard value:Intake side 0.25 mmExhaust side 0.35 mm

Adjustment shim thickness = Thickness of installedshims + (measured value – Standard value)

NOTE The thicknesses of the adjustment shims are between

2.250 – 3.150 mm (37 types which increase in thick-ness by 0.025 mm)

Size identification mark. “2275” = 2.275 mm thickness

NOTEThe piston in the No. 1 cylinder is at the top dead center ofits compression stroke when the protrusion on the cam-shaft reaches its highest position. Rotating the crankshaftone complete turn from that point brings the piston in theNo. 4 cylinder to the top dead center of its compressionstroke.

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DIESEL ENGINE - Engine Basic Mechanisms

3) 4M41 engine

NOTEThe valve clearance check and adjustment should be donewhen the engine is cold.

(1) Remove the rocker cover.(2) Remove all the glow plugs.(3) Use the special tool to turn the crankshaft clockwise, and

align the notch on the crankshaft pulley with timing mark“0” to set the No. 1 cylinder or No. 4 cylinder to the topdead center of its compression stroke.

CautionNever turn the crankshaft anticlockwise, or thetensioner for adjusting the timing chain tension at thetiming gear can be damaged.If it is turned anticlockwise, once remove the tensionerand reinstall.

NOTEIf the projection on the camshaft faces up, the No. 1 cylin-der is on the top dead center of its compression stroke.When the crankshaft is turned just one more turn, the No.4 cylinder is at top dead center.

(4) When the No. 1 or No. 4 piston is on the top dead center ofits compression stroke, use a thickness gauge to mea-sure the valve clearance indicated by the circle in the tablebelow.

When the No. 1 cylinder is at compression top deadcenter:

When the No. 4 cylinder is at compression top deadcenter:

Standard value:Intake side 0.1 mmExhaust side 0.15 mm

NOTEIf the thickness gauge is inserted and pulled out with re-sistance, its reading will be accurate.If the thickness gauge can be inserted and pulled outsmoothly without resistance, its reading will be inaccurate.

(5) If not at the standard value, adjust by the following proce-dure.i. Loosen the lock nut, and tighten the adjusting screw

so that the thickness gauge can be passed with a slightdrag.

Cylinder No. 1 2 3 4

Intake v v – –

Exhaust v – v –

Cylinder No. 1 2 3 4

Intake – – v v

Exhaust – v – v

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DIESEL ENGINE - Engine Basic Mechanisms

ii. After adjustment, tighten the lock nut to the specifiedtorque while preventing the adjusting screw from turn-ing with a screwdriver.

Tightening torque: 9.5 ± 0.5 Nm

iii. Measure the valve clearance again, and check that itis at the standard value.

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DIESEL ENGINE - Fuel System

FUEL SYSTEM

1. Fuel System ProblemsCauses and symptoms of problems

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gnikconktneuqerFgnildielbatsnU

levelnoissimehgiH sagtsuahxeniekomskcalB

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Pub. No. PTEE0113

DIESEL ENGINE - Fuel System

When the fuel filter indicator lamp illuminates, water sepa-rated from the fuel and collected in the filter has reached thelevel at which it must be drained out. Drain the water as fol-lows:(1) Loosen the drain plug.(2) Move the priming pump up and down to allow all the water

to be drained out. Then install the drain plug and tighten itby hand.

2. Draining Water from Fuel Filter

Drain plug

Priming pump

1) Replacement of fuel filter

(1) Remove the intercooler.(2) Remove the fuel tank cap to relieve the pressure in the

fuel tank.(3) Disconnect the water level sensor connector.(4) Disconnect the fuel line heater connector if the vehicle is

equipped with a fuel line heater.(5) Disconnect the fuel hose, then remove the fuel filter.

CautionPlace shop towel or rag around the fuel hose end andfilter to prevent fuel from splashing.

(6) Hold the pump portion of the fuel filter in a vise, then re-move the fuel filter cartridge using a fuel filter wrench.

(7) Hold the water level sensor portion of the removed fuelfilter cartridge in a vise, then turn the cartridge using bothhands to remove the water level sensor.

(8) Install a new fuel filter, then bleed air from the fuel line.(9) Start the engine and check the filter for leakage.

2) Bleeding of fuel line

The fuel line must be bled according to the procedure shownbelow after performing any of the following service operations. When the fuel line is drained and refilled with fuel at the

time of a service operation. When the fuel filter is replaced. When the fuel main hose/pipe is disconnected.(1) Loosen the air plug of the fuel filter.(2) Place a shop towel or rag around the air plug hole and

move the priming pump up and down until air bubbles nolonger emerge from the hole, then tighten the air plug.

(3) Continue moving the priming pump until an increased re-sistance is felt.

Priming pump

<Vehicle without line heater>

Air plug

03E0083

<Vehicle with line heater>

Priming pump

Air plug

03E0074

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DIESEL ENGINE - Fuel System

1) Checking valve opening pressure

(1) Connect the injector to the nozzle tester.(2) Move the lever of the tester two or three times to purge air

from the injector.(3) Move the lever slowly down while watching the pressure

gauge. Read the pressure at the moment when it dropssuddenly after having slowly increased.

Standard value (valve opening pressure):14710 – 15690 kPa 150 – 160 kgf/cm2

(4) If the valve opening pressure is not within the standardpressure range, disassemble and clean the nozzle holder,and replace the shim with a thicker or thinner one to ad-just the valve opening pressure.

NOTE Refer to the Engine Workshop Manual for the disas-

sembly, reassembly and adjustment instructions of thenozzle holder.

Increase of 0.1 mm in the shim thickness correspondsto increase of approximately 1177 – 2157 kPa 12 –22 kgf/cm2 in the valve opening pressure.

2) Checking spray condition

(1) Pump the lever of the nozzle tester in short strokes quickly(at a rate of 4 to 6 strokes per second) and maintain acontinuous spray. The spray must form a narrow and sym-metrical cone (10° in angle) of mist. The spray patternsshown to the left are not acceptable.

3. Inspection and Adjustment of Injector NozzlesCautionNever expose your hands to the fuel spraying out of the nozzle.

A. Excessively largecone angle B. Lopsided

C. Interrupted

(2) Make sure there are no fuel drips from nozzle end afterinjection.

(3) If the injector is found defective as a result of the test,disassemble and clean it before performing the test again.If the injector is still found defective, it must be replaced.

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DIESEL ENGINE - Fuel System

3) Inspection of leakage (fuel tightness)

(1) Slowly move down the lever of the nozzle tester whilewatching the pressure gauge to maintain a pressure of12749 – 13729 kPa 130 – 140 kgf/cm2 for 10 secondsand check that no fuel drips from the shown portions ofthe nozzle.

(2) If the injector is found leaky, disassemble and clean it be-fore performing the test again. If the injector is still foundleaky, it must be replaced.

4) Fuel injection pump assembly installation

Align the notch H in the fuel injection pump gear G to thematch marking “N” <Non-turbo> or “T” <Turbo> on the flangeplate J, and install the fuel injection pump assembly to thetiming gear case.

5) Injection timing inspection and adjustment (4M40)

inspection

(1) Make sure that the push rod E of the special tool pro-trudes 12 mm from the end of the tool body.

(2) Secure the dial indicator with the screw H at the positionwhere the probe of the indicator contacts the push rodand the pointer starts moving.

(3) Be sure to keep the pointer deflection within 0.5 mm.

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DIESEL ENGINE - Fuel System

(4) Turn the crankshaft clockwise again till No. 1 piston is set30° before TDC on the compression stroke.

(5) Zero the dial gauge.

(6) Set No. 1 cylinder piston to the fuel injection timing byturning the crankshaft clockwise. At this point, read thedial gauge to measure the valve lift.

Fuel injection timing:Non-turbo 4° ATDCTurbo 6° ATDC

12° ATDC<Vehicles with inter coolerturbocharger>

Plunger lift: 1 ± 0.03 mm (0.039 ± 0.0012 in.)

Adjustment

(1) Loosen the injection pipe union nut K as well as the bolt Land nut M holding the fuel injection pump in this order.

(2) Use the special tool to loosen the nut L on the crankcaseside.

(3) Adjust the fuel injection timing by tilting the fuel injectionpump assembly right or left till the dial gauge reads thespecified value.

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DIESEL ENGINE - Fuel System

6) Idle speed inspection and adjustment (4M40)

Standard value: 800 ± 100 r/min

7) Throttle opener inspection and adjustment –for A/C (4M40)

01U0056

01U0055Speedometer

Turn on the air-conditioner switch and check whether or nothe engine speed is the standard value.

Standard value: 900 ± 50 rpm

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DIESEL ENGINE - Fuel System

4. Self-regulating Glow System1) System block diagram

Ignition switch

Glow plug relay

Glow indicator lamp

GLOW & EGR control unit• Preheating control• Preheating control as starting• After-glow control• Glow indicator lamp control

Ignition switch-ST

Alternator-L terminal

Coolant temperature sensor

2) Control system schematic diagram

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DIESEL ENGINE - Fuel System

3) Inspection of self-regulating glow system

(1) Make sure the battery voltage is within the range of 11 to13 V.

(2) Make sure the engine coolant temperature is 40°C or lower.

NOTEIf the coolant temperature is higher than 40°C, disconnectthe water temperature sensor connector.

(3) Measure the resistance between the glow plug plate andthe body of each glow plug (ground).

Standard value:0.10 – 0.15 Ω (at 20°C, ceramic-type glow plug)

NOTEThe standard resistance value shown above is for parallelyconnected four glow plugs.

(4) Connect a voltmeter between the glow plug plate and thebody of each glow plug (ground).

(5) Read indication of the voltmeter immediately after turningthe ignition switch to the “ON” position (without startingthe engine).

Standard value:9 – 11 V (should drop to 0 V in 4 to 8 seconds)

Also make sure the preheating indicator lamp (red) comeson when the ignition switch is turned to the “ON” positionand then goes out.

NOTEThe preheating time (glow plug ON time) varies depend-ing on the engine coolant temperature.

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DIESEL ENGINE - Fuel System

Glow plug plate

Glow plug

1.3 Nm0.13 kgm0.9 ft.lbs.

18 Nm1.8 kgm13 ft.lbs.

Checking Glow Plug

Specifications

Description Standard value

Glow plug resistance Metal type 1.0 Ω at 20°C (68°F)Ceramic type 0.5 Ω at 20°C (68°F)(Distinction Mark: Blue paint on theHEX. 12 mm)

Glow plug

Cylinder head

Point of contact

Ohmmeter

Installing Glow Plug

Caution Removal

Use a wrench only to loose the glow plug. Once loose,unscrew the plug with the fingers.

InstallationInsert with fingers before beginning to tighten withthe wrench. Use a 12 mm deep socket.Tighten to 18 Nm (1.8 kgm, 13 ft.lbs.)

HandlingDo not reuse the glow plug if it is dropped on the floorfrom 10 cm (4 in.) height or more.

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DIESEL ENGINE - Fuel System

5. Electronically Controlled EGR SystemTo comply with emission control regulations, the EGR system is electronically controlled.

1) System block diagram

Engine speed sensor

EGR solenoid valve No. 2

EGR solenoid valve No. 1

GLOW & EGR control unit

Lever position sensor

Engine coolant temperature sensor

Power supply (ignition switch)

Transmission type identification switch

2) EGR control system diagram

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DIESEL ENGINE - Fuel System

3) Inspection

(1) Remove, the EGR valve and check it for sticking, depositof carbon, etc.If such condition exists, clean with adequate solvent toensure correct valve seat contact.

(2) Connect a hand vacuum pump to the EGR valve.(3) Apply a vacuum of 500 mmHg (19.7 in.Hg) and check air

tightness.(4) Blow in air from one passage of the EGR to check condi-

tion as follows.

Vacuum Normal condition

20 mmHg (0.8 in.Hg) or lower Air does not blow through

570 mmHg (22.4 in.Hg) or higher Air blows through

(5) Replace the gasket with a new one and tighten the EGRvalve to specified torque.

Tightening torque: 18 Nm

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DIESEL ENGINE - Fuel System

6. Turbocharger1) Inspection of waste gate actuator operation

After installation of the actuator, check that the rod moves approx. 1 mm when approx. 83 kPa (0.84 kg/cm2,11.9 psi) <models without intercooler> or approx. 92 kPa (0.94 kg/cm2, 13.4 psi) <models with intercooler> isapplied to the waste gate actuator using a tester.

2) Other inspection

CautionThe diaphragm incorporated in the waste gate actuatormay break if a pressure exceeding 88 kPa (0.9 kg/cm2,12.8 psi) <models without intercooler> or 108 kPa (1.1kg/cm2, 15.6 psi) <models with intercooler> is applied.

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DIESEL ENGINE - Fuel System

7. Electronically Controlled Fuel Injection System1) System diagram

Battery voltage

Additional control mechanisms on the vehicle

Sensors on the vehicle

Switches on the vehicle

MUT-II

Correction ROM6

2 3 4 5

7

8

1

Engine-ECU

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DIESEL ENGINE - Fuel System

2) System block diagram

Throttle solenoid valve (main)

Throttle solenoid valve (sub)

Glow control relay

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DIESEL ENGINE - Fuel System

3) Throttle valve control

In throttle valve control, the driving condition is detected by means of input signals from the various sen-sors, and the engine-ECU then controls the throttle solenoid valves in accordance with the driving condi-tion to open and close the throttle valve.

1. Starter switch2. Accelerator pedal position sensors

(built-in idle switch)3. Throttle solenoid valves (Main, Sub)4. Vacuum pump5. Throttle body assembly6. Throttle valve7. EGR valve

8. Engine coolant temperature sensor9. Intercooler

10. Engine speed sensor (main)11. Engine speed sensor (backup)12. Injection pump13. Engine-ECU14. Throttle actuator (Main, Sub)

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DIESEL ENGINE - Fuel System

4) System block diagram

5) Throttle valve operation

(1) When engine is stopped

When the ignition switch changes from on to off, the sub throttle solenoid valve turns on for 6 seconds toclose the throttle valve to improve the feeling when the engine stops. After this, the throttle solenoid valveturns off and the throttle valve opens.

(2) When engine starts

The both throttle solenoid valves are normally off, so that the throttle valve is fully open.

(3) When engine is running

The both throttle solenoid valves are normally off, so that the throttle valve is open. However, if the follow-ing conditions occur, the main throttle solenoid valve turns on and the throttle valve partially closes toreduce the engine intake noise.i. Engine coolant temperature ^ 65 – 77°Cii. Barometric pressure > 92 – 94 kPaiii. Engine speed < 1000 r/miniv. Accelerator pedal position sensor output < 1.17 – 2.34%

(4) When a problem develops

The throttle valve partially closes by the main throttle solenoid valve operation if diagnosis code No. 21, 26or 48 is generated.

6) Diagnosis function

(1) Engine warning lamp (Check engine lamp)

Engine warning lamp is lit when any abnormality takesplace in the item related to electronically controlled fuelinjection system shown in the following table.If the malfunction indicator lamp has been on and/or is litwhen the engine is in operation, check the diagnosis out-put.

Engine warning lamp check items

Accelerator pedal position sensor (main)Accelerator pedal position sensor (sub)Boost pressure sensorEngine speed sensorControl sleeve position sensorTimer piston position sensorMain throttle solenoid valveGE actuatorIdle switch (built-in the APS)Engine-ECU

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DIESEL ENGINE - Fuel System

(2) Self diagnosis code

CautionIf the above-mentioned diagnosis code number with the asterisks can be displayed along with an-other code number in parentheses simultaneously, check the other code number before replacing theengine-ECU.12 (41, 49), 25 (43), 26 (48), 41 (12, 49), 48 (26), 49 (12, 41)

Code No. Diagnosis item

11 Accelerator pedal position sensor (main) system

12* Boost pressure sensor system

13 Barometric pressure sensor (ECU built-in) system

14 Fuel temperature sensor system

15 Engine coolant temperature sensor system

16 Boost air temperature sensor system

17 Vehicle speed sensor system

18 Engine speed sensor (backup) system

21 Engine speed sensor system

23 Idle switch (accelerator pedal position sensor built-in) system

25* Timer piston position sensor system

26* Control sleeve position sensor system

27 Accelerator pedal position sensor (sub) system

41* Main throttle solenoid valve system

43 Timing control valve system

46 Injection correction ROM system

48* GE actuator (in the middle of control sleeve position sensor inoperative) system

49* Over boost (turbocharger waste gate malfunction)

54 Immobilizer system

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DIESEL ENGINE - Fuel System

(3) Fail-safe, backup functions

When abnormalities in the major sensors are detected by diagnosis functions, pre-set control logic oper-ates to maintain a safe driving condition for the vehicle.

Diagnosis item Control features in malfunctionAccelerator pedal position sensor Accelerator pedal released (idle switch ON)

Acceleration opening degree = 0%Accelerator pedal applied (idle switch OFF)

Engine controlled at low speedAcceleration opening degree = 20% fixed

Idle switch Void idling speed control.Void cruise control.

Engine speed sensor Engine controlled at low speedVoid cruise control.

Boost air temperature sensor Controls as if the intake air temperature is 50°C.Vehicle speed sensor Void idling speed control.

Void cruise control.Engine coolant temperature sensor Controls as if the engine coolant temperature is 80°C.Control sleeve position sensor Engine controlled at low speed

Void cruise controlTimer piston position sensor Injection timing stabilizing control

Void cruise control.Barometric pressure sensor (ECU Controls as if the barometric pressure is 101 kPa.built-in)Fuel temperature sensor Controls as if the fuel temperature is 50°C.Boost pressure sensor Controls as if the boost pressure as barometric pressure (101 kPa).Injection correction ROM Void correction.GE actuator Engine controlled at low speed

Void cruise control.Over boost Void cruise control.Timing control valve Injection timing stabilizing control

Void cruise control.

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Troubleshooting

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TROUBLESHOOTING - Troubleshooting Procedures

Troubleshooting ProceduresGenerally speaking, engine failures occur in two major areas: the first area includes mechanical componentssuch as intake/exhaust valves and pistons; the other area includes electric/electronic components that relateto control of the ignition, fuel injection, and idle speed control (ISC) systems.There are no ways to determine in a single step whether a trouble is mechanical or electric/electronic. For thisreason, it is common troubleshooting practice to first diagnose the trouble thoroughly to identify the suspectsystem, and then locate faulty component(s) within that system.

1.Trouble occured

2.Interview the customer and reproduce the trouble

3.Read and analyze service data

AInspect suspect system (determine trouble cause)

BPerform repair

CTest repaired system for normal operation

DPerform initialization drive(learning)

EExplain performed service and repair to customer

4.Perform basic inspection

5.Perform actuator tests

DiagnosisBasic inspection

ServiceRepair

ConfirmationPrevention of recurrence

Completion

1. Trouble occured2. Interview the customer and reproduce the trouble

Understand the trouble clearly and accurately.3. Read and analyze service data

Read diagnosis codes using the MUT-II and analyze relevant service data.4. Perform basic inspection

Inspect the system’s maintenance items and basic functions (adjustment items, oil level, spark condition,fuel supply condition, etc.)

5. Perform actuator testsCarry out the actuator test using MUT-II.

Carrying out steps 1 to 5 above will enable you to identify the suspect system.

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TROUBLESHOOTING - Troubleshooting Procedures

A. Inspect suspect systemThoroughly inspect the suspect system by checking all the components one after another to identify faultycomponents.

B. Perform repairTake steps most appropriate for restoring normal operation of the system, such as part replacement,adjustment, and rectification.

C. Test repaired system for normal operationPerform an operation test of the system to make sure the trouble has been completely resolved.

D. Perform initialization driveWith engine control systems employing an electronically controlled, the engine-ECU needs to gather datawhich it uses as thresholds to determine the condition of the system and make necessary correctionsbased on them. Gathering such data requires actual running of the vehicle for a specified period of time.This process corresponds to the running-in operation of a mechanical system.

E. Explain performed service and repair to customerMake documents of specified forms, recording the performed service and repair operations. Explain to thecustomer what has been carried out in a manner that precludes complaints, fear, and distrust. This com-pletes the series of service and repair operation.

+=TroubleshootingDiagnosis

(locating suspect system)

Identifying trouble cause (screening faulty components through systematic inspection)

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TROUBLESHOOTING - Interview

InterviewThe first step of troubleshooting a trouble is to correctly identify the trouble without prejudice in order to beable to make appropriate decision of the troubleshooting steps that should be followed. The trouble can bereadily identified if its symptom is evident. However, the symptom of a trouble of which the customer com-plains is not always apparent. It may be unnoticeable when the vehicle is brought to the workshop. If this is thecase, you must try to reproduce the trouble using all methods practicable.Even an experienced technician can miss important points or make wrong decisions if he/she goes aheadwith troubleshooting without first identifying the trouble.Reproduction of a trouble is possible only when the selected method is appropriate for the trouble. For in-stance, a trouble that occurs only when the engine is cold cannot be reproduced when the engine is at anoperating temperature. Trying to reproduce a trouble resulting from road-input-caused vibration has no effectif a test is performed with the vehicle stopped. To be effective for a trouble reproducing test, it is essential to“interview the customer,” asking him/her for the specific conditions in which the trouble occurred.

Key Points for Interview

Listed below are the five key points you should bear in mind when interviewing a customer. During an inter-view, you should try to gather information as much as possible including, for example, information on troublesthat occurred in the past and service/repair history of the vehicle which may be helpful for troubleshootingeven if the data appear irrelevant to the trouble. Examine the data collected through the interview in search forrelationship with the trouble. Needless to say, questions should not be random but should be narrowed downto the system that appears most responsible for the trouble according to estimates from symptoms. The useof a customer interview form will help facilitate the interview.

Reproducing the trouble

Veteran technicians often say “Troubleshooting is almost over if you can reproduce and ascertain the trouble.”Learning the situation in which the trouble occurred from the customer through an interview and reproducingthe trouble in a similar situation is essential for successful troubleshooting.

* Refer to the “Trouble Reproducing Methods” section.

Key points for interview

1. What ...............................Vehicle model, engine model

2. When ..............................Date, time, and frequency of occurrence of trouble

3. Where .............................Road conditions

4. In what conditions ...........Driving conditions, maneuvering conditions, weather

5. How ................................How the trouble was perceived by the customer.

* Refer to the example of customer interview form on the next page.

Interview: What, When, Where, In what conditions, How

Reproduction of trouble: It is essential to reproduce the trouble.

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TROUBLESHOOTING - Interview

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TROUBLESHOOTING - Trouble Reproducing Methods

Trouble Reproducing MethodsAs explained earlier, what is indispensable for successful troubleshooting is to interview the customer forthorough description of the trouble and, based on the information thus obtained, reproduce the trouble bysubjecting the vehicle to conditions similar to those in which the trouble has actually occurred.Troubles that are difficult to reproduce include those caused by such factors as vibration, heat, and water(moisture). Artificially imposing these factors may be necessary to reproduce these types of trouble.

Points to Respect in Trouble ReproductionYou must be able through trouble reproduction tests not only to ascertain symptoms of the trouble but also toidentify the faulty system or location (part).To achieve this, you must estimate the responsible system and connect to it an appropriate tester and othermeasuring equipment before starting the test. Using the data thus collected together with the symptomsobserved, you will be able to determine whether the suspect system is really faulty.

Trouble reproduction by giving vibration

Use this method for troubles that are likely to be caused by vibration.

1. Small parts:Give the suspect part light movements by hand while checking for occurrence of the trouble symptom.

2. Wiring harnesses and connectors:Lightly shake the suspect harness or connector in vertical and horizontal directions while checking foroccurrence of the trouble symptom. Give shakes especially to the root of a connector, the point aroundwhich the item vibrates, and the portion of the item that passes through a hole in a vehicle body compo-nent.

3. Others:For the engine and transmission that are elastically mounted on the body, carry out stall test to give themdisplacement forces. A vibrating machine is also usable for the purpose.

Trouble reproduction by cooling/heating the item

Use this method for troubles that occur only when the engine is cold or at operating temperature.

1. Heat or cool the component items of the suspect system using a hair dryer or refrigerant while checking foroccurrence of the trouble symptom. When heating an item, do not exceed its maximum permissible temperature limit.

2. Simulate a cold engine by replacing coolant or removing the thermostat.Trouble reproduction by water sprayingUse this method for troubles that occur only in rainy days or after the vehicle is washed.Spray water over the vehicle while checking for occurrence of the trouble symptom. Do not spray water directly into the engine compartment. Instead, spray water onto the radiator from

outside to indirectly cause the temperature and humidity in the engine compartment to change. Do not spray water directly onto electronic parts. Rain water may run along wiring harnesses and enter the engine-ECU or other electronic parts. Those

harnesses which can come into contact with rain water should be sprayed with water for appropriatelylong time to make sure whether they relate with the trouble.

NOTEWhile the interview should be the primary method to make rough estimate of possible causesof the trouble, making reference to troubleshooting tables in workshop manuals also helps tofind the causes.

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Trouble reproduction by creating conditions similar to those reported by the customer

Use this method when the customer reported the specific conditions of the trouble through the interview.

1. Use every possible means to place the vehicle under the conditions similar to those in which the customerclaims the trouble occurred. These include adjusting the engine load, electric loads, gear in engagement,and vehicle speed.

2. It is also necessary to take into consideration individual customer’s habits, sensitive and feeling tenden-cies, and what level of quality he/she is asking for.

Trouble reproduction methods:Cause every possible physical changes in suspect items based on customer interview data.

TROUBLESHOOTING - Trouble Reproducing Methods

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Self-DiagnosisThe first step you should perform in troubleshooting any electronically controlled system is to identify thefaulty system(s) using self-diagnosis results before trying to find faulty components.With an electrical trouble, bypassing this step and starting with fault finding tests can end up in temporaryrecovery of a normal condition, preventing you from identifying the real cause.

1. Diagnosis

Faulty systems can be identified using diagnosis codes stored in the engine-ECU memory.When using diagnosis codes, it is necessary for you to determine whether the indicated diagnosis code isactive (the corresponding fault still exists) or non-active (the fault occurred in the past but no longer exists).To determine whether the indicated diagnosis code is active or non-active, erase the code, reproduce thetrouble condition and make sure of it by the symptom that accompanies it, and then check whether thediagnosis code reappears. If the code is non-active, it will not reappear. If the code is active, it will appearagain.In addition to diagnosis codes, you can use for finding faulty system the service data which are also providedfrom the engine-ECU as described below.

2. Service Data

Read engine-ECU input and output data while a fault condition is present. In most cases, these data includemore than one abnormalities. Record all of the data and use them together with the results of inspection ofother items to make a comprehensive determination of a faulty system. Do not rely on only the abnormal datayou find first.

Self-diagnosis code checking steps

Read diagnosis code

Record and erase the diagnosis code

Reproduce trouble

Perform trouble reproducing tests using an appropriate method

Read diagnosis code

Diagnosis code not displayedFault condition is present

Narrow down to a suspect system by performing the basic functional inspection,

service data reading, and actuator test

Check suspect system(If narrowing down is unsuccessful,

perform symptom by symptom inspection)

Diagnosis code not displayedFault condition is not present

(Past fault)

First diagnosis codesSystem inspection

Diagnosis code displayedFault condition is present

Check the system corresponding to the displayed code

Reproduction possible

Reproduction impossible

* 1 Refer to the “Trouble Reproducing Methods” section.

Service data: In most cases, more than one abnormal data are displayed one after another.

Diagnosis code: Erase and check again.

TROUBLESHOOTING - Self-Diagnosis

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Basic Functional InspectionMost of the mechanical engine parts cannot be self-diagnosed. However, mechanical faults can often affectelectric/electronic control systems, and this sometimes cause abnormal service data to be output. Therefore,service data do not necessarily indicate electric/electronic faults.For instance, if damaged cylinder head gasket causes gas to blow by and misfire occurs in one of the cylin-ders, the electronic control system will open the ISC valve to make the amount of intake air increase tomaintain the standard engine speed. If the service data are checked under this condition, both air flow sensor’sand ISC valve’s output data deviate from the standard values towards their maximum levels, possibly makinga technician believe that the air flow sensor and ISC servo are faulty.To avoid the possibility of being misled to a false estimation due to such mechatronic interaction, you mustalways perform inspection of the basic functions for all systems and use the results together with other infor-mation to make a comprehensive determination of a suspect system.The basic functional inspection refers to inspection of the entire system including mechanical and electroniccomponents for proper operations. In the example above in which misfire occurs in one cylinder, basic func-tional inspection results will tell you that all of the inspection items are normal except the compression pres-sure.The basic functional inspection includes the following six items of inspection:

Basic functional inspection: Essentials for good gasoline engine performanceSufficient compression pressure, strong sparks at proper timing, and appropriate air-fuel ratios

Basic functional inspection items1. Compression pressure

Measure the compression pressure. (Compression pressure can be roughly checked byobserving the cranking operation.)

2. FuelCheck if the injectors are being supplied with fuel (by feeling the return hose pressure).* GDI engines: Check the service data item “fuel pressure.”

3. Injector operationCheck the operating sound of injectors using a sound scope.* Diesel engines: Operate injectors.

4. Spark plugsCheck sparks.

5. ISC valveCreate a condition that makes the engine operate at a fast idle speed and make sure theengine speed actually changes.

6. OthersCheck battery voltage, fuse condition, engine oil level, fuel quality, etc.

TROUBLESHOOTING - Basic Functional Inspection

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Actuator TestWhile modern engines’ mechatronic systems use highly sophisticated control technology and means, theiroutput end components (actuators) that convert electric signals into mechanical motion have rather simpleconstructions and functions.These components use essentially either electromagnetic coils (motors and solenoids) or lamp bulbs. Eachsystem uses multiple actuators each making simple motion, and combination of simple motions creates ac-tions necessary for the system to achieve its function. For example, the fuel pump uses the motor’s rotatingmotion, the solenoid valve create intermittent open and close motions for injectors.A fault occurs if any of these actuators fails to operate normally. In other words, a failure indicates that at leastone actuator is faulty.Therefore, troubleshooting starts with checking every actuator for normal operation and isolating a one that isin faulty condition.

Actuator test methods

Many of the actuators can be tested using the MUT-II. The others must be checked by operating them manu-ally or using other means.What is important is to determine whether the fault exists in the actuator and the components downstream ofit or in the electronic circuit components including the engine-ECU that control the actuator. For this purpose,the output control signal voltage at the “control terminal” located between the engine-ECU and the actuatormust be checked.For instance, let us assume a case in which you operate the MUT-II to drive the fuel pump but it does not run.Since the engine-ECU’s control does not cover beyond the control terminal at the fuel pump relay, if you testsnormal the voltage of the control signal from the terminal, the fault exists in a part downstream of the relay, notin the control circuit.In short, you need to check the actuator for normal operation and, if its operation is not normal, then you needto determine whether the fault exists in the engine-ECU side or in the actuator side.

NOTEIf an input sensor of the control system is faulty, an actuator that operates according to the sensor’s signaloperates abnormally.

It is important to know that the engine-ECU has a built-in diagnostic function which monitors sensor inputsand sets a fault code if it judges a sensor to be faulty, so you should be able to determine whether any sensoris faulty or not before you start troubleshooting steps as long as you do not neglect checking diagnostic codes.When encountering an actuator that operates abnormally, you should be able to tell if it is caused by anactuator fault or by a sensor fault unless you fail to follow the diagnostic code checking steps faithfully.

Actuator test: Determine on which side a fault exists, the engine-ECU side or actuator side.

Actuator test items1. Engine control relay

Operate manually.2. Fuel pump relay

Can be tested using the MUT-II.3. Fuel pressure solenoid

Can be tested using the MUT-II.4. Injector driver relay

Operate manually.5. Injector

Can be tested using the MUT-II.

6. Ignition coilOperate manually.

7. ISC servo systemOperate manually.

8. EGR solenoidCan be tested using the MUT-II.

9. Variable air intake servo systemCan be tested using the MUT-II.

10. Other actuatorsAll must be inspected.

TROUBLESHOOTING - Actuator Test

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Troubleshooting Tree - Gasoline Engine

TROUBLESHOOTING - Troubleshooting Tree - Gasoline Engine

Trouble

Compression

Engine basic components

CylindersWear, scoring, faulty gasket, etc.

Pistons and connecting rods

Wear, scoring, bend, etc.

Valve mechanism

Drive and timing mechanism

Timing belt, sprocket, cam lobe, lash adjuster, timing switch mechanism, valve clearance, tensioner, etc.

ValvesValve seat, valve stem, stem seal, etc.

Ignition

Primary Coil, power transistor, etc.

SecondaryCoil, high-tension cables, plugs, etc.

Air-fuel mixture

Fuel

PumpLow- and high- pressure pumps, control relay, etc.

LineFilter, piping, pressure regulator, etc.

Pressure regulation

Pressure regulator, vacuum hose, solenoid, etc.

InjectorInjector, resistor, driver, relay, etc.

QualityOctane number, foreign matter, additive, etc.

Air

Line

Duct, hose, air cleaner, intake manifold, turbocharger, air bypass valve, relief valve, waste gate valve, solenoid, etc.

Throttle valveThrottle valve, relay, control unit (ETV), fixed SAS, SAS, etc.

ISC ISC, harness, etc.

Emission control and mixture control

PCV system, air bypass solenoid valve, EGR system, purge control valve, canister, brake booster, oxygen sensor, catalytic converter, etc.

ControlECU, sensor, wiring, relay, external noise, etc.

OtherStarting system, cooling system, etc.

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Inspections to Narrow Down Suspect Systems

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TROUBLESHOOTING - Inspections to Narrow Down Suspect Systems

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TROUBLESHOOTING - Inspections to Narrow Down Suspect Systems

Page 90: Troubleshooting Engines

83

Pub. No. PTEE0113

TROUBLESHOOTING - Troubleshooting Note

Troubleshooting Note

noitcesesicrexE .oN denialpmocmetsyS

.1 tnialpmoC :tisivecivresfoetaD

__________________________

:ybnettirW

__________________________

:ledomelciheV

__________________________

.2 noitcudorpermelborp/weivretnifostluseR

.3 kcehcedocsisongaidfostluseR :omeM

.4 stluserdnademrofrepnoitarepo-)nwodgniworranmetsystcepsus(noitcepsnicisaB

.5 stluserdnasmetitset-tsetrotautcA

.A metsystcepsuS

stluserdnasmetikcehc-kcehcmetsystcepsuS

esuaC

.B demrofrepriapeR tahwdnanraeluoydidtahWebotyrassecenknihtuoyod

?detcerroc/devorpmi

________ __________________

__________________________

__________________________

__________________________

__________________________

__________ ________________

.C nurtseT

.D )ni-gninnur(setunim01tuobarofdeepselditanuR

.E remotsucotnoitanalpxE

Page 91: Troubleshooting Engines

emanremotsuCnoitartsigeR

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etad

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____________________________________________________________srehtO

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srehtO

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____________________________________________________________srehtO

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edocsisongaiDecnerruccotsriF l oN l )(SEY

ecnerruceR l oN l )(SEY

CUSTOMER INTERVIEW FORM

Page 92: Troubleshooting Engines

Troubleshooting Note

noitcesesicrexE .oN denialpmocmetsyS

.1 tnialpmoC :tisivecivresfoetaD

__________________________

:ybnettirW

__________________________

:ledomelciheV

__________________________

.2 noitcudorpermelborp/weivretnifostluseR

.3 kcehcedocsisongaidfostluseR :omeM

.4 stluserdnademrofrepnoitarepo-)nwodgniworranmetsystcepsus(noitcepsnicisaB

.5 stluserdnasmetitset-tsetrotautcA

.A metsystcepsuS

stluserdnasmetikcehc-kcehcmetsystcepsuS

esuaC

.B demrofrepriapeR tahwdnanraeluoydidtahWebotyrassecenknihtuoyod

?detcerroc/devorpmi

________ __________________

__________________________

__________________________

__________________________

__________________________

__________ ________________

.C nurtseT

.D )ni-gninnur(setunim01tuobarofdeepselditanuR

.E remotsucotnoitanalpxE