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Product: EXCAVATORModel: 235 EXCAVATOR 81XConfiguration: 235 EXCAVATOR 81X00001UP (MACHINE) POWERED BY3306 ENGINE

Systems Operation 3306 DIRECT INJECTION ENGINE FOR CATERPILLAR BUILT MACHINESMedia Number SENR205703 Publication Date 01/12/1992 Date Updated 17/10/2001

Systems Operation

IntroductionNOTE: For Specifications with illustrations, make reference to Specifications for 3306 Direct Injection Vehicular Engine With New Scroll FuelSystem, Form No. SENR2056. If the Specifications in Form SENR2056 are not the same as in the Systems Operation and the Testing and Adjusting,look at the printing date on the back cover of each book. Use the Specifications given in the book with the latest date.

Engine Design

Cylinder And Valve Location

Bore ... 120.7 mm (4.75 in.)

Stroke ... 152.4 mm (6.00 in.)

Number of Cylinders ... 6

Cylinder Arrangement ... in line

Valves per Cylinder ... 2

Combustion ... Direct Injection

Firing Order (Injection Sequence) ... 1, 5, 3, 6, 2, 4

Rotation of Crankshaft (when seen from flywheel end) ... counterclockwise

NOTE: The No. 1 cylinder is opposite the flywheel end.

Fuel System

Fuel Flow

Fuel System Schematic (1) Fuel tank. (2) Fuel return line. (3) Priming pump. (4) Fuel injection nozzle. (5) Fuel injection line. (6) Fuel injection pump. (7) Primary fuel filter. (8) Check valves. (9) Fueltransfer pump. (10) Secondary fuel filter. (11) Constant bleed valve. (12) Fuel injection pump housing.

Fuel is pulled from fuel tank (1) through primary fuel filter (7) and check valves (8) by fuel transfer pump (9). From the fuel transfer pump the fuel ispushed through secondary fuel filter (10) and to the fuel manifold in fuel injection pump housing (12). A bypass valve in the fuel transfer pump keepsthe fuel pressure in the system at 25 to 40 psi (170 to 280 kPa). Constant bleed valve (11) lets a constant flow of fuel go through fuel return line (2)

back to fuel tank (1). The constant bleed valve returns approximately 9 gal. (34 liters) per hour of fuel and air to the fuel tank. This helps keep the fuelcool and free of air. There is also a manual bleed valve that can be used when the fuel priming pump is used to remove air from the system. Fuelinjection pump (6) gets fuel from the fuel manifold and pushes fuel at very high pressure through fuel line (5) to fuel injection nozzle (4). The fuelinjection nozzle has very small holes in the tip that change the flow of fuel to a very fine spray that gives good fuel combustion in the cylinder.

Fuel Injection Pump

The fuel injection pump increases the pressure of the fuel and sends an exact amount of fuel to the fuel injection nozzle. There is one fuel injectionpump for each cylinder in the engine.

The fuel injection pump is moved by cam (14) of the fuel pump camshaft. When the camshaft turns, the cam raises lifter (11) and pump plunger (6) tothe top of the stroke. The pump plunger always makes a full stroke. As the camshaft turns farther, spring (8) returns the pump plunger and lifter to thebottom of the stroke.

When the pump plunger is at the bottom of the stroke, fuel at transfer pump pressure goes into inlet passage (2), around pump barrel (4) and to bypassclosed port (5). Fuel fills the area above the pump plunger.

After the pump plunger begins the up stroke, fuel will be pushed out the bypass closed port until the top of the pump plunger closes the port. As thepump plunger travels farther up, the pressure of the fuel increases. At approximately 100 psi (690 kPa), check valve (1) opens and lets fuel flow intothe fuel injection line to the fuel injection nozzle. When the pump plunger travels farther up, scroll (9) uncovers spill port (10). The fuel above thepump plunger goes through slot (7), along the edge of scroll (9) and out spill port (10) back to fuel manifold (3). This is the end of the injection stroke.The pump plunger can have more travel up, but no more fuel will be sent to the fuel injection nozzle.

Fuel Injection Pump (1) Check valve. (2) Inlet passage. (3) Fuel manifold. (4) Pump barrel. (5) Bypass closed port. (6) Pump plunger. (7) Slot. (8) Spring. (9) Scroll. (10) Spill port. (11) Lifter. (12) Fuelrack. (13) Gear. (14) Cam.

When the pump plunger travels down and uncovers bypass closed port (5), fuel begins to fill the area above the pump plunger again, and the pump isready to begin another stroke.

The amount of fuel the injection pump sends to the injection nozzle is changed by the rotation of the pump plunger. Gear (13) is attached to the pumpplunger and is in mesh with fuel rack (12). The governor moves the fuel rack according to the fuel needs of the engine. When the governor moves thefuel rack, and the fuel rack turns the pump plunger, scroll (9) changes the distance the pump plunger pushes fuel between bypass closed port (5) andspill port (10) opening. The longer the distance from the top of the pump plunger to the point where scroll (9) uncovers spill port (10), the more fuelwill be injected.

To stop the engine, the pump plunger is rotated so that slot (7) on the pump plunger is in line with spill port (10). The fuel will now go out the spillport and not to the injection nozzle.

Fuel Injection Nozzle

The fuel injection nozzle goes through the cylinder head into the combustion chamber. The fuel injection pump sends fuel with high pressure to thefuel injection nozzle where the fuel is made into a fine spray for good combustion.

Fuel Injection Nozzle (1) Carbon dam. (2) Seal. (3) Passage. (4) Filter screen. (5) Orifice. (6) Valve. (7) Diameter. (8) Spring.

Seal (2) goes against the cylinder head and prevents leakage of compression from the cylinder. Carbon dam (1) keeps carbon out of the bore in thecylinder head for the nozzle.

Fuel with high pressure from the fuel injection pump goes into the inlet passage. Fuel then goes through filter screen (4) and into passage (3) to thearea below diameter (7) of valve (6). When the pressure of the fuel that pushes against diameter (7) becomes greater than the force of spring (8), valve(6) lifts up. This occurs when the fuel pressure goes above the Valve Opening Pressure of the fuel injection nozzle. When valve (6) lifts, the tip of thevalve comes off the nozzle seat and the fuel will go through orifices (5) into the combustion chamber.

The injection of fuel continues until the pressure of fuel against diameter (7) becomes less than the force of spring (8). With less pressure againstdiameter (7), spring (8) pushes valve (6) against the nozzle seat and stops the flow of fuel to the combustion chamber.

The fuel injection nozzle cannot be disassembled and no adjustments can be made.

Fuel Transfer Pump (7N6831)

Fuel Transfer Pump Schematic (Up Stroke) (1) Bypass valve. (2) Pumping spring. (3) Small piston. (4) Outlet. (5) Inlet check valve. (6) Push plate. (7) Pumping check valve. (8) Outlet check valve. (9) Large piston. (10) Pushrod.

The fuel transfer pump is a twopiston pump that is moved by a cam (eccentric) on the camshaft for the fuel injection pump. The transfer pump islocated on the right side of the fuel injection pump housing.

When the camshaft turns, the cam lifts push rod (10) up. The push rod lifts large piston (9), push plate (6) and small piston (3). As the pistons moveup, inlet check valve (5) and outlet check valve (8) close. Pumping check valve (7) in the large piston opens and fuel goes through the holes in thebottom of the large piston and fills the passages and chamber between the bottom of the large piston and outlet check valve (8). As small piston (3)moves up, the pressure of the fuel above the piston increases and flows out of the pump through outlet (4).

Fuel Transfer Pump Schematic (Down Stroke) (1) Bypass valve. (2) Pumping spring. (3) Small piston. (4) Outlet. (5) Inlet check valve. (6) Push plate. (7) Pumping check valve. (8) Outlet check valve. (9) Large piston. (10) Pushrod.

As the camshaft continues to turn, the cam lowers push rod (10) down. Pumping spring (2) pushes small piston (3), push plate (6) and large piston (9)down. When the piston moves down, inlet check valve (5) and outlet check valve (8) open. Pumping check valve (7) in the large piston closes and thepressure of the fuel below the check valve increases. Fuel now flows through the outlet check valve. A part of the fuel goes through outlet (4) and theremainder goes to the area above small piston (3).

As the large piston moves down, fuel from the fuel tank is pulled through inlet check valve (5) into the area between the large and small piston. Thepump is now ready to start a new cycle.

Bypass valve (1) controls the outlet pressure of the fuel. If the fuel pressure goes beyond 170 to 280 kPa (25 to 40 psi), the bypass valve opens andfuel flows to the inlet of the pump.

Fuel Transfer Pump (1W1695)

The fuel transfer pump is a piston pump that is moved by a cam (eccentric) on the camshaft for the fuel injection pump. The transfer pump is locatedon the bottom side of the fuel injection pump housing.

Fuel Transfer Pump (Start Of Down Stroke) (Arrows Indicate Fuel Flow Direction)

(1) Push rod. (2) Piston. (3) Outlet check valve. (4) Pumping check valve. (5) Pumping spring. (6) Pump inlet port. (7) Inlet check valve. (8) Pump outlet port.

When the fuel injection pump camshaft turns, the cam moves push rod (1) and piston (2) down. As the piston moves down, inlet check valve (7) andoutlet check valve (3) close. Pumping check valve (4) opens and allows the fuel below the piston to move into the area above the piston. Pumpingspring (5) is compressed as the piston is pushed down by push rod (1).

As the fuel injection pump camshaft continues to turn, the cam no longer puts force on push rod (1). Pumping spring (5) now moves piston (2) up.This causes pumping check valve (4) to close. Inlet check valve (7) and outlet check valve (3) will open. As the piston moves up, the fuel in the areaabove the piston is pushed through the outlet check valve (3) and out pump outlet port (8). Fuel also moves through pump inlet port (6) and inletcheck valve (7) to fill the area below piston (2). The pump is now ready to start a new cycle.

Fuel Transfer Pump (Start Of Up Stroke) (Arrows Indicate Fuel Flow Direction) (1) Push rod. (2) Piston. (3) Outlet check valve. (4) Pumping check valve. (5) Pumping spring. (6) Pump inlet port. (7) Inlet check valve. (8) Pump outlet port.

Oil Flow For Fuel Pump And Governor

Oil from the side of the cylinder block goes to support (9) and into the bottom of front governor housing (4). The flow of oil now goes in three

different directions.

A part of the oil goes to the rear camshaft bearing in fuel pump housing (5). The bearing has a groove around the inside diameter. Oil goes through thegroove and into the oil passage in the bearing surface (journal) of camshaft (7). A drilled passage through the center of the camshaft gives oil to thefront camshaft bearing and to the thrust face of the camshaft drive gear. Drain hole (6) in the front of fuel pump housing (5) keeps the level of the oilin the housing even with the center of the camshaft. The oil returns to the oil pan through the timing gear housing.

Fuel Pump And Governor (1) Cover. (2) Servo. (3) Rear governor housing. (4) Front governor housing. (5) Fuel pump housing. (6) Drain hole. (7) Camshaft. (8) Drain hole. (9) Support.

Oil also goes from the bottom of the front governor housing through a passage to the fuel pump housing and to governor servo (2). The governorservo gives hydraulic assistance to move the fuel rack.

The remainder of the oil goes through passages to the rear of rear governor housing (3), through cover (1) and back into another passage in the rear

governor housing. Now the oil goes into the compartment for the governor controls. Drain hole (8) keeps the oil at the correct level. The oil in thiscompartment is used for lubrication of the governor control components and the oil is the supply for the dashpot.

The internal parts of the governor are lubricated by oil leakage from the servo and the oil is thrown by parts in rotation. The flyweight carrier thrustbearing gets oil from the passage at the rear of the camshaft.

Oil from the governor returns to the oil pan through a hole in the bottom of the front governor housing and through passages in the support andcylinder block.

Governor

The governor controls the amount of fuel needed by the engine to maintain a desired rpm.

Governor (1) Governor spring. (2) Sleeve. (3) Valve. (4) Piston. (5) Governor servo. (6) Fuel rack. (7) Lever. (8) Flyweights. (9) Over fueling spring. (10) Riser. (11) Spring seat. (12) Stop bolt.(13) Torque spring. (14) Power setting screw. (15) Torque rise setting screw. (16) Stop collar. (17) Stop bar.

The governor flyweights (8) are driven directly by the fuel pump camshaft. Riser (10) is moved by flyweights (8) and governor spring (1). Lever (7)connects the riser with sleeve (2) which is fastened to valve (3). Valve (3) is a part of governor servo (5) and moves piston (4) and fuel rack (6). Thefuel rack moves toward the front of the fuel pump housing (to the right in the illustration) when moved in the FUEL OFF direction.

The force of governor spring (1) always pushes to give more fuel to the engine. The centrifugal (rotating) force of flyweights (8) always push to get areduction of fuel to the engine. When these two forces are in balance (equal), the engine runs at a constant rpm.

When the engine is started and the governor is at the low idle position, over fueling spring (9) moves the riser forward and gives an extra amount offuel to the engine. When the engine has started and begins to run, the flyweight force becomes greater than the force of the over fueling spring. Theriser moves to the rear and reduces the amount of fuel to the low idle requirement of the engine.

When the governor control lever is moved to the high idle position, governor spring (1) is put in compression and pushes riser (10) toward theflyweights. When the riser moves forward, lever (7) moves sleeve (2) and valve (3) toward the rear. Valve (3) stops oil flow through governor servo(5) and the oil pressure moves piston (4) and the fuel rack to the rear. This increases the amount of fuel to the engine. As engine speed increases, theflyweight force increases and moves the riser toward the governor spring. When the riser moves to the rear, lever (7) moves sleeve (2) and valve (3)forward. Valve (3) now directs oil pressure to the rear of piston (4) and moves the piston and fuel rack forward. This decreases the amount of fuel tothe engine. When the flyweight force and the governor spring force become equal, the engine speed is constant and the engine runs at high idle rpm.High idle rpm is adjusted by the high idle adjustment screw. The adjustment screw limits the amount of compression of the governor spring.

With the engine at high idle, when the load is increased, engine speed will decrease. Flyweights (8) move in and governor spring (1) pushes riser (10)forward and increases the amount of fuel to the engine. As the load is increased more, govenor spring (1) pushes riser (10) farther forward. Spring seat(11) pulls on stop bolt (12). Stop collar (16) on the opposite end has power setting screw (14) and torque rise setting screw (15) that control themaximum amount of fuel rack travel. The power setting screw moves forward and makes contact with torque spring (13). This is the full load balancepoint. If more load is added to the engine, engine speed will decrease and push riser (10) forward more. This will cause power setting screw (14) tobend (deflect) torque spring (13) until torque rise setting screw (15) makes contact with stop bar (17). This is the point of maximum fuel to the engine.

Governor Servo

The governor servo gives hydraulic assistance to the mechanical governor force to move the fuel rack. The governor servo has cylinder (3), cylindersleeve (4), piston (2) and valve (1).

Governor Servo (Fuel On Position) (1) Valve. (2) Piston. (3) Cylinder. (4) Cylinder sleeve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the governor moves in the FUEL ON direction, valve (1) moves to the left. The valve opens oil outlet (B) and closes oil passage (D). Pressureoil from oil inlet (A) pushes piston (2) and fuel rack (5) to the left. Oil behind the piston goes through oil passage (C), along valve (1) and out oiloutlet (B).

Governor Servo (Balanced Position) (1) Valve. (2) Piston. (3) Cylinder. (4) Cylinder sleeve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the governor spring and flyweight forces are balanced and the engine speed is constant, valve (1) stops moving. Pressure oil from oil inlet (A)pushes piston (2) until oil passages (C and D) are opened. Oil now flows through oil passage (D) along valve (1) and out through oil outlet (B). Withno oil pressure on the piston, the piston and fuel rack (5) stop moving.

Governor Servo (Fuel Off Position) (1) Valve. (2) Piston. (3) Cylinder. (4) Cylinder sleeve. (5) Fuel rack. (A) Oil inlet. (B) Oil outlet. (C) Oil passage. (D) Oil passage.

When the governor moves in the FUEL OFF direction, valve (1) moves to the right. The valve closes oil outlet (B) and opens oil passage (D).Pressure oil from oil inlet (A) is now on both sides of piston (2). The area of the piston is greater on the left side than on the right side of the piston.The force of the oil is also greater on the left side of the piston and moves the piston and fuel rack (5) to the right.

Dashpot

The dashpot helps give the governor better speed control when there are sudden speed and load changes. The dashpot has cylinder (1), piston (2),dashpot spring (3), needle valve (5) and check valve (6). Piston (2) and spring seat (4) are fastened to dashpot spring (3).

Dashpot (Governor Moving to Fuel On)

(1) Cylinder. (2) Piston. (3) Dashpot spring. (4) Spring seat. (5) Needle valve. (6) Check valve. (7) Oil reservoir.

When the governor moves toward FUEL ON, spring seat (4) and piston (2) move to the right. This movement pulls oil from oil reservoir (7) throughcheck valve (6) and into cylinder (1).

Dashpot (Governor Moving to Fuel Off) (1) Cylinder. (2) Piston. (3) Dashpot spring. (4) Spring seat. (5) Needle valve. (6) Check valve. (7) Oil reservoir.

When the governor moves toward FUEL OFF, spring seat (4) and piston (2) move to the left. This movement pushes oil out of cylinder (1), throughneedle valve (5) and into oil reservoir (7).

If the governor movement is slow, the oil gives no restriction to the movement of the piston and spring seat. If the governor movement is fast in theFUEL OFF direction, the needle valve gives a restriction to the oil and the piston and spring seat will move slowly.

Air Inlet And Exhaust SystemThe air inlet and exhaust system components are: air cleaner, inlet manifold, cylinder head, valves and valve system components, exhaust manifoldand turbocharger.

Air Inlet And Exhaust System (1) Exhaust manifold. (2) Inlet manifold pipe. (3) Engine cylinders. (4) Air inlet. (5) Turbocharger compressor wheel. (6) Turbocharger turbine wheel. (7) Exhaust outlet.

Clean inlet air from the air cleaner is pulled through the air inlet (4) of the turbocharger by the turning compressor wheel (5). The compressor wheelcauses a compression of the air. The air then goes to the inlet manifold (2) of the engine. When the intake valves open, the air goes into the enginecylinder (3) and is mixed with the fuel for combustion. When the exhaust valves open, the exhaust gases go out of the engine cylinder and into theexhaust manifold (1). From the exhaust manifold, the exhaust gases go through the blades of the turbine wheel (6). This causes the turbine wheel andcompressor wheel to turn. The exhaust gases then go out the exhaust outlet (7) of the turbocharger.

Turbocharger And Aftercooler

Turbocharger And Aftercooler Installed (1) Aftercooler housing. (2) Exhaust outlet. (3) Turbine wheel housing. (4) Air outlet. (5) Compressor wheel housing. (6) Air inlet. (7) Cylinder head. (8) Exhaust manifold. (9)Exhaust inlet. (10) Cylinder bore.

Aftercooler (1) Aftercooler housing. (3) Turbine wheel housing. (4) Air outlet. (7) Cylinder head.

The aftercooler cools the air coming out of the turbocharger before it goes into the inlet manifold. The purpose of this is to make the air going into thecombustion chambers more dense. The more dense the air is, the more fuel the engine can burn efficiently. This gives the engine more power.

Turbocharger (1) Aftercooler housing. (2) Exhaust outlet. (3) Turbine wheel housing. (4) Air outlet. (5) Compressor wheel housing. (6) Air inlet. (8) Exhaust manifold. (9) Exhaust inlet.

Turbocharger

The turbocharger is installed on the exhaust manifold. All the exhaust gases from the engine go through the turbocharger.

Turbocharger (Typical Example) (1) Air inlet. (2) Compressor housing. (3) Nut. (4) Compressor wheel. (5) Thrust bearing. (6) Center housing. (7) Lubrication inlet passage. (8) Turbine housing. (9) Sleeve. (10)Turbine wheel. (11) Exhaust outlet. (12) Sleeve. (13) Oil deflector. (14) Bearing. (15) Lubrication outlet passage. (16) Bearing. (17) Exhaust inlet.

The exhaust gases enter the turbine housing (8) and go through the blades of turbine wheel (10), causing the turbine wheel and compressor wheel (4)to turn.

When the compressor wheel turns, it pulls filtered air from the air cleaners through the compressor housing air inlet. The air is put in compression byaction of the compressor wheel and is pushed to the inlet manifold of the engine.

When engine load increases, more fuel is injected into the engine cylinders. The volume of exhaust gas increases which causes the turbochargerturbine wheel and compressor impeller to turn faster. The increased rpm of the impeller increases the quantity of inlet air. As the turbochargerprovides additional inlet air, more fuel can be burned. This results in more horsepower from the engine.

Maximum rpm of the turbocharger is controlled by the rack setting, the high idle speed setting and the height above sea level at which the engine is

operated.

NOTICEIf the high idle rpm or the fuel setting is higher than given in the FuelSetting And Releated Information Fiche (for the height above sea levelat and which the engine is operated), there can be damage to engine orturbocharger parts. Damage will result when increased heat and/orfriction, due to the higher engine output, goes beyond the enginecooling and lubrication systems abilities.

The bearings for the turbocharger use engine oil for lubrication. The oil comes in through the lubrication inlet passage (7) and goes through passagesin the center section for lubrication of the bearings. Oil from the turbocharger goes out through the lubrication outlet passage (15) in the bottom of thecenter section and goes back to the engine lubrication system.

Cylinder Head And Valves

There is one cylinder head for all cylinders. Each cylinder has one intake and one exhaust valve. Each intake and exhaust valve has a valve rotator.The valve rotator causes the valve to turn a small amount each time the valve opens and closes. This action helps keep carbon deposits off of the valveface and valve seat.

The cylinder head has valve seats installed and they can be replaced.

The valve guides can be replaced. There are threads on the inside diameter of the valve guides to hold oil that lubricates the valve stem.

Valve Mechanism

The valve mechanism controls the flow of inlet air and exhaust gases in and out of the cylinders. The valve mechanism consists of rocker arms, pushrods, valve lifters and camshaft.

The camshaft is driven by and timed to the crankshaft. When the camshaft turns, the camshaft lobes move the valve lifters up and down. The valvelifters move the push rods which move the rocker arms. Movement of the rocker arms make the intake and exhaust valves open according to the firingorder (injection sequence) of the engine. A valve spring for each valve makes the valve go back to the closed position and holds it there.

Lubrication SystemSystem Oil Flow

Lubrication System Schematic (Engine Warm)

(1) Oil passage (to front idler gear). (2) Oil passage (to turbocharger and fuel injection pump). (3) Rocker arm shaft. (4) Oil pressure connection. (5) Oil manifold. (6) Piston coolingorifices. (7) Camshaft bearing bore. (8) Oil cooler bypass valve. (9) Oil filter bypass valve. (10) Engine oil cooler. (11) Oil filter. (12) Turbocharger. (13) Oil pump. (14) Oil pan.

Oil pump (13) pulls oil from oil pan (14) and then pushes the oil to oil cooler (10). From the oil cooler the oil goes to oil filter (11) and then to oilmanifold (5). From the oil manifold, oil goes to all main bearings, and piston cooling orifices (6). Oil passages in the crankshaft send oil to theconnecting rod bearings. Oil from the front main bearing goes through oil passage (1) to the bearing for the fuel injection pump idler gear. Oil fromthe front main bearing also goes to camshaft bearing bore (7). The front camshaft bearing is the only bearing to get pressure lubrication.

Oil passage (2) from No. 4 main bearing sends oil to turbocharger (12) and the fuel injection pump housing on the right side of the engine.

An oil passage from the rear of the cylinder block goes below the head bolt hole and connects with a drilled passage that goes up next to the head bolthole. A hollow dowel connects the vertical oil passage in the cylinder block to the oil passage in the head. The spacer plate has a hole with acounterbore on each side that the hollow dowel goes through. An Oring is in each counterbore to prevent oil leakage around the hollow dowel. Oilflows through the hollow dowel into a vertical passage in the cylinder head to the rocker arm shaft bracket. The rocker arm shaft has an orifice torestrict the oil flow to the rocker arms. The rear rocker arm bracket also has an Oring that seals against the head bolt. This seal prevents oil fromgoing down around the head bolt and leaking past the head gasket or spacer plate gasket. The Oring must be replaced each time the head bolt isremoved from the rear rocker arm bracket.

Rocker Arm Oil Supply

Holes in the rocker arm shafts let the oil give lubrication to the valve system components in the cylinder head. After the lubrication oil has done itswork, it goes back to the engine oil pan.

There is a bypass valve in the oil pump. This bypass valve controls the pressure of the oil coming from the oil pump. The oil pump can put more oilinto the system than is needed. When there is more oil than needed, the oil pressure increases and the bypass valve will open. This allows the oil thatis not needed to go back to the engine oil pan.

With the engine cold (starting conditions), bypass valves (8 and 9) will open and give immediate lubrication to all components when cold oil withhigh viscosity causes a restriction to the oil flow through oil cooler (10) and oil filter (11). Oil pump (13) sends the cold oil through the bypass valvesaround the oil cooler and oil filter to oil manifold (5) in the cylinder block.

When the oil gets warm, the pressure difference in the bypas valves decreases and the bypass valves close. Now there is a normal flow of oil throughthe oil cooler and oil filter.

The bypass valves will also open when there is a restriction in the oil cooler or oil filter. This action does not let an oil cooler or oil filter with arestriction prevent lubrication of the engine.

Flow Of Oil (Engine Cold) (8) Oil cooler bypass. (9) Oil filter bypass. (10) Engine oil cooler. (11) Oil filter. (12) Turbocharger. (13) Oil pump. (14) Oil pan.

Cooling SystemCoolant Flow (Engine With Water Cooled Turbocharger)

Coolant Flow (Engine With Water Cooled Turbocharger) (1) Radiator. (2) Inlet line to radiator. (3) Turbocharger vent line. (4) Water temperature regulator. (5) Return line from turbocharger. (6) Inlet line to turbocharger. (7) Cylinderhead. (8) Cylinder block. (9) Inlet line to water pump. (10) Water pump. (11) Internal bypass. (12) Engine oil cooler. (13) Elbow. (14) Cylinder liner.

Water pump (10) is on the left front of the engine. The water pump is gear driven by the front timing gears. The rotation of the impeller in the waterpump pushes coolant through the cooling system.

Coolant from the bottom of radiator (1) is pulled through inlet line (9) by water pump (10). The water pump pushes coolant to engine oil cooler (12).Coolant flows from the engine oil cooler through elbow (13) into the side of cylinder block (8) and flows around cylinder liners (14) and up through

the coolant directors into cylinder head (7). The coolant directors make the coolant flow around the valves and around the exhaust ports (passages) inthe cylinder head. The coolant now goes to the front of the cylinder head. At the front of the cylinder head water temperature regulator (4) controls thedirection of the coolant flow. If the coolant temperature is less than normal for engine operation, the water temperature regulator is closed. Thecoolant must go through internal bypass (11) to the water pump. When the coolant gets to the temperature of normal operation the water temperatureregulator opens and most of the coolant flows through radiator inlet line (2) to the radiator. A part of the coolant still goes through internal bypass(11).

NOTE: The water temperature regulator (4) is an important part of the cooling system. It divides coolant flow between radiator (1) and internalbypass (11) as necessary to maintain the correct temperature. If the water temperature regulator is not installed in the system, there is no mechanicalcontrol, and most of the coolant will take the path of least resistance through the bypass. This will cause the engine to overheat in hot weather. In coldweather, even the small amount of coolant that goes through the radiator is too much, and the engine will not get to normal operating temperatures.

Coolant goes from elbow (13) through line (6) to the center housing of the turbocharger. Coolant flows through return line (5) from the turbochargerto the cylinder head. There is a vent line (3) from the turbocharger to the radiator to let any air in the cooling system go to the top of the radiator.When coolant is put into the cooling system, air is pushed out through vent line (3) into the top of the radiator.

Coolant Flow (Engine Without Aftercooler)

Coolant Flow (Engine Without Aftercooler) (1) Radiator. (2) Pressure cap. (3) Inlet line to radiator. (4) Water temperature regulator. (5) Cylinder head. (6) Cylinder block. (7). Inlet line to water pump. (8) Water pump. (9)Internal bypass (shunt) line. (10) Engine oil filter. (11) Engine oil cooler. (12). Elbow. (13) Cylinder liner.

The water pump (8) is on the front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of the radiator (1) goes to thewater pump inlet. The rotation of the impeller in the water pump (8) pushes the coolant through the system.

All of the coolant flow from the water pump (8), goes through the engine oil cooler (11). The elbow (12) on the outlet side of the engine oil cooler(11) connects to the side of the cylinder block (6). The coolant enters the block and flows around cylinder liners (13) and up through the coolant

directors into cylinder head (5). The coolant directors make the coolant flow around the valves and around the exhaust ports (passages) in the cylinderhead. The coolant now goes to the front of the cylinder head. At the front of the cylinder head water temperature regulator (4) controls the direction ofthe coolant flow. If the coolant temperature is less than normal for engine operation, the water temperature regulator is closed. The coolant must gothrough internal bypass (9) to the water pump. When the coolant gets to the temperature of normal operation the water temperature regulator opensand most of the coolant flows through radiator inlet line (3) to the radiator. A part of the coolant still goes through internal bypass (9).

Coolant Flow (Engine With Aftercooler)

Coolant Flow (Engine With Aftercooler) (1) Radiator. (2) Pressure cap. (3) Inlet line for radiator. (4) Aftercooler. (5) Aftercooler inlet line. (6) Return line from aftercooler. (7) Internal bypass (shunt) line. (8) Water pump.(9) Inlet line for water pump. (10) Engine oil cooler. (11) Bonnet.

Water pump (8) is on the left front side of the engine. It is gear driven by the timing gears. Coolant from the bottom of radiator (1) goes to the waterpump inlet. The rotation of the impeller in water pump (8) pushes the coolant through the system.

The coolant flow from the water pump (8) is divided. Some goes through engine oil cooler (10). Bonnet (11) on the outlet side of engine oil cooler(10) connects to the side of the cylinder block. The coolant enters the block and flows around the cylinder liners and up through the coolant directorsinto the cylinder head.

The coolant directors make the coolant flow around the valves and around the exhaust ports (passages) in the cylinder head. The coolant now goes tothe front of the cylinder head. At the front of the cylinder head water the temperature regulator controls the direction of the coolant flow. If the coolanttemperature is less than normal for engine operation, the water temperature regulator is closed. The coolant must go through internal bypass (7) to thewater pump. When the coolant gets to the temperature of normal operation the water temperature regulator opens and most of the coolant flowsthrough radiator inlet line (3) to the radiator. A part of the coolant still goes through internal bypass (7).

The remainder of the coolant flow goes through aftercooler inlet line (5) into the core of aftercooler (4). The core of aftercooler (4) is a group of platesand fins. The coolant goes through the plates. The inlet air for the engine goes around the fins. This cools the inlet air. The coolant comes out of theaftercooler (4) at the rear of the engine and goes through return line (6) to bonnet (11) on engine oil cooler (10). It mixes with the rest of the coolantfrom engine oil cooler (10) in bonnet (11) and goes into the cylinder block.

Cooling System Components

Water Pump

The centrifugaltype water pump has two seals, one prevents leakage of water and the other prevents leakage of lubricant.

An opening in the bottom of the pump housing allows any leakage at the water seal or the rear bearing oil seal to escape.

Fan

The fan is driven by two Vbelts, from a pulley on the crankshaft and the fan drive. Belt tension is adjusted by moving the alternator.

Basic Block

Cylinder Block And Liners

A steel spacer plate is used between the cylinder head and the block to eliminate liner counterbore and to provide maximum liner flange support area(the liner flange sits directly on the cylinder block).

Engine coolant flows around the liners to cool them. Three Oring seals at the bottom and a filler band at the top of each cylinder liner form a sealbetween the liner and the cylinder block.

Pistons, Rings And Connecting Rods

The piston has three rings; two compression and one oil ring. All rings are located above the piston pin bore. The two compression rings seat in aniron band which is cast into the piston. Pistons in some engines use compression rings with straight sides. Pistons in other engines use compressionrings which are of the KEYSTONE type. KEYSTONE rings have a tapered shape and the movement of the rings in the piston groove (also of taperedshape) results in a constantly changing clearance (scrubbing action) between the ring and the groove. This action results in a reduction of carbondeposit and possible sticking of rings.

The oil ring is a standard (conventional) type and is spring loaded. Holes in the oil ring groove provide for the return of oil to the crankcase.

The piston pin bore in the piston is offset (moved away) from the center of the piston 0.76 mm (.030 in.). The full floating piston pin is held in thepiston by two snap rings which fit into grooves in the piston pin bore.

The piston pin end of the connecting rod is tapered to give more bearing surface at the area of highest load. The connecting rod is installed on thepiston with the bearing tab slots on the same side as the "V" mark on the piston.

Crankshaft

The crankshaft changes the combustion forces in the cylinder into usable rotating torque which powers the machine. There is a gear at the front of thecrankshaft that drives the timing gears and the engine oil pump. The connecting rod bearing surfaces get oil for lubrication through passages drilled inthe crankshaft. A lip type seal and wear sleeve is used to control oil leakage in the front crankshaft seal. A hydrodynamic grooved seal assembly isused to control rear crankshaft oil leakage. The hydrodynamic grooves in the seal lip move lubrication oil back into the crankcase as the crankshaftturns.

Vibration Damper

The twisting of the crankshaft, due to the regular power impacts along its length, is called twisting (torsional) vibration. The vibration damper is

installed on the front end of the crankshaft. It is used for reduction of torsional vibrations and stops the vibration from building up to amounts that cancause damage.

Cross Section Of A Vibration Damper (Typical Example) (1) Flywheel ring. (2) Rubber ring. (3) Inner hub.

The damper is made of a flywheel ring (1) connected to an inner hub (3) by a rubber ring (2). The rubber makes a flexible coupling between the

flywheel ring and the inner hub which reduces the vibrations of the crankshaft.

Electrical SystemThe engine electrical system has three separate circuits: the charging circuit, the starting circuit and the low amperage circuit. Some of the electricalsystem components are used in more than one circuit. The battery (batteries), disconnect switch, circuit breaker, ammeter, cables and wires from thebattery are all common in each of the circuits.

The charging circuit is in operation when the engine is running. An alternator makes electricity for the charging circuit. A voltage regulator in thecircuit controls the electrical output to keep the battery at full charge.

NOTICEThe disconnect switch, if so equipped, must be in the ON position to letthe electrical system function. There will be damage to some of thecharging circuit components if the engine is running with thedisconnect switch in the OFF position.

If the machine has a disconnect switch, the starting circuit can operate only after the disconnect switch is put in the ON position.

The starting circuit is in operation only when the start switch is activated.

The low amperage circuit and the charging circuit are both connected to the same side of the ammeter. The starting circuit connects to the oppositeside of the ammeter.

Charging System Components

NOTICENever operate the alternator without the battery in the circuit. Makingor breaking an alternator connection with heavy load on the circuit cancause damage to the regulator.

Alternator (DelcoRemy)

The alternator is driven by Vbelts from the crankshaft pulley. This alternator is a three phase, selfrectifying charging unit, and the regulator is part ofthe alternator.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carrycurrent are stationary. The conductors are: the field winding, stator windings, six rectifying diodes, and the regulator circuit components.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (likepermanent magnets) that produce a small amount of magnetlike lines of force (magnetic field) between the poles. As the rotor assembly begins toturn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the smallmagnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through thediodes of the rectifier bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent to thefield windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force.These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly alsoincreases the current and voltage output of the alternator.

The voltage regulator is a solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system and switches on and off manytimes a second to control the field current (DC current to the field windings) for the alternator to make the needed voltage output.

DelcoRemy Alternator (1) Regulator. (2) Roller bearing. (3) Stator winding. (4) Ball bearing. (5) Rectifier bridge. (6) Field winding. (7) Rotor assembly. (8) Fan.

Alternator (Bosch)

The alternator is driven by Vbelts from the crankshaft pulley. This alternator is a three phase, selfrectifying charging unit. The regulator is part of thealternator.

Bosch Alternator (1) Fan. (2) Stator winding. (3) Field winding. (4) Regulator. (5) Ball bearing. (6) Roller bearing. (7) Rotor. (8) Rectifier assembly.

This alternator design has no need for slip rings or brushes, and the only part that has movement is the rotor assembly. All conductors that carrycurrent are stationary. The conductors are: the field winding, stator windings, six rectifying diodes, and the regulator circuit components.

The rotor assembly has many magnetic poles like fingers with air space between each opposite pole. The poles have residual magnetism (likepermanent magnets) that produce a small amount of magnetlike lines of force (magnetic field) between the poles. As the rotor assembly begins toturn between the field winding and the stator windings, a small amount of alternating current (AC) is produced in the stator windings from the smallmagnetic lines of force made by the residual magnetism of the poles. This AC current is changed to direct current (DC) when it passes through thediodes of the rectifier bridge. Most of this current goes to charge the battery and to supply the low amperage circuit, and the remainder is sent to thefield windings. The DC current flow through the field windings (wires around an iron core) now increases the strength of the magnetic lines of force.These stronger lines of force now increase the amount of AC current produced in the stator windings. The increased speed of the rotor assembly alsoincreases the current and voltage output of the alternator.

The voltage regulator is a solid state (transistor, stationary parts) electronic switch. It feels the voltage in the system and switches on and off manytimes a second to control the field current (DC current to the field windings) for the alternator to make the needed voltage output.

Alternator (Nippondenso)

The alternator is driven by Vbelts from the crankshaft pulley. The Nippondenso alternator has threephase, fullwave rectified output. It is brushless.The rotor and bearings are the only moving parts. The regulator is part of the alternator.

Nippondenso Alternator (1) Fan. (2) Front frame assembly. (3) Stator assembly. (4) Rotor assembly. (5) Field winding (coil assembly). (6) Regulator assembly. (7) Condenser (suppression capacitor). (8)Rectifier assembly. (9) Rear frame assembly.

When the engine is started and the rotor turns inside the stator windings, threephase alternating current (AC) and rapidly rising voltage is generated.

A small amount of alternating current (AC) is changed (rectified) to pulsating direct current (DC) by the exciter diodes on the rectifier assembly.Output current from these diodes adds to the initial current which flows through the rotor field windings from residual magnetism. This will make therotor a stronger magnet and cause the alternator to become activated automatically. As rotor speed, current and voltages increase, the rotor fieldcurrent increases enough until the alternator becomes fully activated.

The main battery charging current is charged (rectified) from AC to DC by the other positive and negative diodes in the rectifier and pack (mainoutput diodes) which operate in a full wave linkage rectifier circuit.

Alternator output is controlled by a regulator, which is inside the alternator rear frame.

Alternator Regulator (DelcoRemy)

Regulator (DelcoRemy)

The voltage regulator is an electronic switch. It feels the voltage in the system and gives the necessary field current (current to the field windings ofthe alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current to the alternator by switching on and offmany times a second.

Alternator Regulator (Bosch)

Regulator (Bosch)

The voltage regulator is an electronic switch. It feels the voltage in the system and gives the necessary field current (current to the field windings ofthe alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current to the alternator by switching on and offmany times a second.

Alternator Regulators (Nippondenso)

Regulator (Nippondenso)

The regulator is fastened to the alternator by two different methods. One method fastens the regulator to the top, rear of alternator. With the othermethod the regulator is fastened separately by use of a wire and a connector that goes into the alternator.

The voltage regulator is a solid state (transistor, no moving parts) electronic switch. It feels the voltage in the system and gives the necessary fieldcurrent (current to the field windings of the alternator) for the alternator to make the needed voltage. The voltage regulator controls the field current tothe alternator by switching on and off many times a second. There is no voltage adjustment for this regulator.

Starting System Components

Solenoid

A solenoid is a magnetic switch that does two basic operations.

a. Closes the high current starter motor circuit with a low current start switch circuit.b. Engages the starter motor pinion with the ring gear.

Typical Solenoid Schematic

The solenoid switch is made of an electromagnet (one or two sets of windings) around a hollow cylinder. There is a plunger (core) with a spring loadinside the cylinder that can move forward and backward. When the start switch is closed and electricity is sent through the windings, a magnetic fieldis made that pulls the plunger forward in the cylinder. This moves the shift lever (connected to the rear of the plunger) to engage the pinion drive gearwith the ring gear. The front end of the plunger then makes contact across the battery and motor terminals of the solenoid, and the starter motor beginsto turn the flywheel of the engine.

When the start switch is opened, current no longer flows through the windings. The spring now pushes the plunger back to the original position, and atthe same time, moves the pinion gear away from the flywheel.

When two sets of windings in the solenoid are used, they are called the holdin windings and the pullin windings. Both have the same number ofturns around the cylinder, but the pullin windings uses a larger diameter wire to produce a greater magnetic field. When the start switch is closed,part of the current flows from the battery through the holdin windings, and the rest flows through the pullin windings to motor terminal, thenthrough the motor to ground. When the solenoid is fully activated (connection across battery and motor terminal is complete), current is shut offthrough the pullin windings. Now only the smaller holdin windings are in operation for the extended period of time it takes to start the engine. Thesolenoid will now take less current from the battery, and heat made by the solenoid will be kept at an acceptable level.

Starter Motor

The starter motor is used to turn the engine flywheel fast enough to get the engine to start running.

The starter motor has a solenoid. When the start switch is activated, the solenoid will move the starter pinion to engage it with the ring gear on theflywheel of the engine. The starter pinion will engage with the ring gear before the electric contacts in the solenoid close the circuit between thebattery and the starter motor. When the circuit between the battery and the starter motor is complete, the pinion will turn the engine flywheel. A clutchgives protection for the starter motor so that the engine cannot turn the starter motor too fast. When the start switch is released, the starter pinion willmove away from the ring gear.

Starter Motor Cross Section (1) Field. (2) Solenoid. (3) Clutch. (4) Pinion. (5) Commutator. (6) Brush assembly. (7) Armature.

Other Components

Circuit Breaker

Circuit Breaker Schematic (1) Reset button. (2) Disc in open position. (3) Contacts. (4) Disc. (5) Battery circuit terminals.

The circuit breaker is a switch that opens the battery circuit if the current in the electrical system goes higher than the rating of the circuit breaker.

A heat activated metal disc with a contact point makes complete the electric circuit through the circuit breaker. If the current in the electrical systemgets too high, it causes the metal disc to get hot. This heat causes a distortion of the metal disc which opens the contacts and breaks the circuit. Acircuit breaker that is open can be reset (an adjustment to make the circuit complete again) after it becomes cool. Push the reset button to close thecontacts and reset the circuit breaker.

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