Cummins Engine Company History (Modified From Cummins.com) Clessie Cummins is an Indiana born automotive pioneer. Most notably, Cummins has been recognized as the person who introduced the automotive diesel to the United States. He founded and was president for 19 years of the diesel engine company bearing his name. Clessie's adventures started in 1904 when he quit school in the eighth grade and stated, "I want to be a machinist and make things". He worked for a short time around central Indiana in four early automotive related industries before settling at Nordyke and Marmon which produced the Marmon car. He was also on the pit crew of the first winner of the Indianapolis 500 mile race, Ray Harroun, who drove a Marmon Wasp to victory lane on May 30, 1911. Cummins worked in an assortment of jobs, participated in motoring and "started making things" during his early adulthood. Then on February 3, 1919, the Cummins Engine Company was incorporated with Clessie Cummins and W.G. Irwin, who once employed Cummins as his chauffeur, being the principle shareholders. Clessie Cummins first two diesel patents were applied for in 1921. They were both for improvements in fuel injection on engines built under license. Production of the Cummins model F engine began in 1925 with injection components of Clessie's design used in marine and lighthouse applications. On Christmas Day, 1929—he took W.G. Irwin for a ride in America’s first diesel-powered automobile.In a Society of Automotive Engineers meeting in April 1929, Clessie predicted "the common use of diesel engines for motorcars is not near. Eventually it will come, but there is no economic need for it now." Little did he know that the Great Depression would start six months later and provide the economic need for energy-efficient transportation choices. The genesis of his promotional efforts started with the installation of a model U engine in a 1925 Packard seven-passenger limousine for a long distance road test and publicity tour. The car crossed the US using a mere $11.22 worth of fuel. In 1931, a Cummins team set a new endurance record—a grueling 13,535 miles—at the Indianapolis Motor Speedway. Impressed with the economy and durability of these prototypes, a small number of truckers and fleet operators began to re-power their vehicles with Cummins engines.

The “Jake brake” was another of his innovations. After a harrowing ride down a steep hill after the service brakes failed on a truck he was driving he vowed he would design an engine-powered brake. Production began in 1959 of the compression release brake. It was built under contract to Jacobs manufacturing – maker of drill chucks and other industrial products.

In the 1950s, America embarked on a massive interstate highway construction program. Cummins engines powered much of the equipment that built the roads, and thousands of the trucks that began to roll down them. Truckers demanded economy, power, reliability, and durability, and Cummins responded. By combining lab-based research and field-based trials—including dramatic performances at the Indy 500 races—Cummins achieved technological breakthroughs, including the revolutionary PT (pressure-time) fuel injection system of 1954. By the late 1950s, Cummins had sales of over $100 million and a commanding lead in the market for heavy truck diesels. Clessie Cummins died in August 1968. Cummins has been the market leader in truck engines since the early ‘70’s until today.

CUMMINS PT SYSTEM

The pressure-time (PT) diesel fuel system is manufactured exclusively by Cummins Engine Company for their engines. Cummins engines introduced the PT fuel system in 1951. It replaced another Cummins fuel system, which was called the double-disc system. The then newer PT system was a much simpler design and application and also contained fewer moving parts. In 1980 until the early ‘90’s Cummins lead the industry by outselling all other manufacturers in worldwide sales (greater than 200hp) using the Cummins PT system. Cummins fuel systems have developed since to partial electronic control incorporating the original PT system. In approximately 1990 however it became clear that the PT system would not be certified under the ever more stringent emissions standards. Cummins switched to a version of EUI, (CELECT), and then developed their HPI-TP, (ISX), system that is a return to a system similar to the original PT system but fully computer controlled. Basic Operation

Cummins PT fuel system's first model was the PT flange-type injector and a PTR (pressure time regulator)-type pump. This PT system uses a principle that is based on pressure time. The pressure supplied to the injector is provided by a by a variable low-pressure gear pump. The pump outflow is regulated by engine speed. Time allowed for fuel measuring is controlled by the injector plunger, which opens and closes a metering orifice. This time is determined by the speed of the engine, since the injector plunger is engine camshaft driven so the time factor is not variable, it is a mechanical function of engine speed. The slower the engine RPM – more time is given to allow fuel to flow under pressure into the injector body. The out flow of the pump is the variable factor and by precisely controlling the fuel pressure, the engine speed and horsepower can be regulated.

The higher the pressure in the fuel rail, the more fuel that will be metered in a given amount of time. If pressure is increased and time (rpm) is held constant, more fuel is metered into the injector cup and therefore, injected into the cylinders. The system has a built-in torque rise because as the engine lugs down to its peak torque range there is more time for metering. Injectors and pumps have changed over the years as engine horsepower and exhaust emission requirements changed. From the initial flange-type in-jector other injector models were developed. The PT cylindrical injector, first introduced with internal fuel line engines, was a cylindrical (round) injector and utilized the same basic principle as the flange-type PT. Also, the later PTD injector used an adjusting nut that controlled its upward travel. This injector is called the PTD top stop. By allowing the injector valve train to unload when the injector plunger was up against the top stop nut, more lubrication could get into the areas between all the moving linkages. Fewer adjustments are required and longer injector train service life is possible. The original pump model PTR has been replaced by the PTG pump, which differs from the PTR pump in several ways. The most important difference is the method of fuel manifold pressure regulation. In the PTR pump, a separate pressure regulator controlled maximum fuel manifold pressure. In the PTG the regulator has been eliminated and maximum fuel manifold pressure is controlled by the governor; hence the designation PTG. The PTG was the standard Cummins pump for many years had an external aneroid device. It was replaced by the PTG AFC pump (1977 production until early ‘90’s). A device somewhat similar to an aneroid is built into the pump. An aneroid is a flow no-flow bypass valve that is operated by air pressure from the intake manifold. The AFC device differs by by providing a controlled or modulated increase in fuel flow as boost pressures increase.

The biggest problem of the PTG external aneroid pump was that it had poor engine acceleration. Until the engine built-up manifold boost pressure, only a small amount of fuel was delivered to the injectors. The aneroid behaved as an on off device. The PTG AFC pump could modulate fuel flow under various boost conditions. Components of PTG-AFC

A. A gear pump- mounted on the rear of the pump housing. This pump operates to draw fuel from the tank through the filter housing. Fuel moves out the pressure side of the pump to supply the throttle shaft and the governor assembly.

B. The filter screen and magnet is located between the gear pump and other internal

pump components. Metal particles that may originate in the pump and any other contaminants are filtered out.

C. Pump housing provides a place for all the pump components.

D. Pulsation dampener at the rear of the pump housing is a steel diaphragm that

absorbs pulsations created by the gear pump. Because it is a gear pump, its output is delivered in a series of pulses as each gear tooth set releases its slug of fuel. If not dampened this would cause fluctuating rail pressures and rough engine operation because of uneven fueling

E. The throttle controls the engine speed between low and high idle speed when a

limiting speed governor is used. On pumps using variable speed governors, it allows the operator to adjust engine speed to operating conditions

F. Two basic governor types, the limiting-speed governor and the variable-speed

governor, are used on Cummins fuel pumps. Cummins sometimes calls them the automotive type governor and the mechanical variable-speed (MVS) governor. The automotive type is used on Cummins engines in trucks, while the MVS governor is used on any application where governor control over the entire engine speed range is required. Both of the governors used are mechanical-type

G. A special tach drive has been incorporated into the pump housing for the engine

tachometer. The tachometer cable or electric tachometer-sending unit can be connected directly to it. The drive coupling is mounted on the pump main drive

shaft. The drive coupling has three tangs on it that are engaged into a rubber or plastic spider and installed on the engine, which has a similar drive coupling.

H. The engine shutdown solenoid is an electrically operated valve, mounted on top

of the pump that allows the operator to start and stop the engine with the vehicle ignition switch. When electricity is supplied to it, the shutdown valve is open and allows fuel to flow to the injectors. When the electricity is shut off, the fuel flow to the injectors is stopped, causing the engine to shut down. The valve is equipped with a knob that allows it to be operated manually if the power supply should be lost. To operate the valve manually, the knob (mounted on the forward end of the solenoid) must be turned all the way clockwise. Electric operation from the key switch requires that it must be turned all the way out (counterclockwise).

I. The AFC (air-fuel control) device controls the air-fuel ratio of the engine under

varying load and speed conditions. It is operated by intake manifold pressure and spring pressure.

PUMP IDENTIFICATION

When pump servicing is required, identification of the pump must be made to ensure correct repair and calibration procedures. Pump DATAPLATE Explanation. All Cummins pumps have a data-plate attached to them when they are manufactured or rebuilt. This nameplate contains a code that is used for looking up the proper fuel pump setting in the fuel system data book. Several types of nameplates have been used over the years as pump models and identification procedures changed.

Pump Operation and fuel flow

Governor Operation at idle Fuel is pulled through the fuel sub-system by the gear pump. Pressure waves caused by the gear pump are smoothed out by the pulsation damper. Fuel is forced through an internal filter consisting of a mesh and a magnet. Fuel enters the governor assembly through the supply port in the governor barrel. The governor weights generate little centrifuge at idle speed and therefore the governor plunger (which rotates within the governor barrel) is in a position where both the idle and main ports are in register with the recessed annular area of the plunger - fuel at supply pressure will exit through the idle and main ports. Because the governor plunger is centre and cross-drilled, supply pressure will also act on the governor button, separating it, and re-circulate fuel to the bypass circuit. Fuel from the governor assembly arrives at the throttle assemble from the idle and main passages. However, the throttle is in the idle fuel position which locates the throttle fuel orifice out of register with the main port; a small quantity of fuel is permitted to pass through the throttle fuel orifice and this is known as throttle leakage. Fuel from the idle passage is permitted to bypass the throttle shaft. Most of the idle fuel quantity bypasses the throttle shaft in this manner. Fuel from the throttle assembly is ducted to the AFC circuitry. However, at idle speed there is little or no manifold boost to act on the AFC diaphragm; accordingly the AFC plunger is in the closed position. The flow area defined by the no-air set screw setting is the total flow area feeding the rail pipe. Fuel is ducted from the AFC circuitry and exits the P.T. pump through the solenoid to which the rail pipe is connected.

Governor Operation anywhere in the torque curve Pressure within the defined flow area represented by the duct feeding the governor barrel will be higher as the positive displacement gear pump is being rotated at a higher speed. Fuel enters the governor assembly through the governor barrel supply port and circulates in the annular recess of the governor plunger. However, due to the higher rpm and greater centrifugal force generated by the flyweights, the governor plunger has been driven inboard into the barrel sufficiently to take the idle passage out of register with the plunger recessed annulus. Supply fuel exits the governor barrel through the main passage and also acts on the governor button, spilling fuel to the bypass for re-circulation. This action moderates supply pressure. The torque spring is now a factor, this helps resist further inboard plunger travel towards a diminished fuel position. Fuel from the governor is ducted to the throttle assembly by the main passage. As the engine is running somewhere within the torque rise profile, the throttle shaft is positioned so there is some degree of register of the fuel orifice with the main passage, defining a flow area. Fuel flows from the throttle assembly to the AFC circuitry. As before, it flows up to and around the no air set screw, but now there is sufficient manifold boost acting on the AFC diaphragm to have overcome the AFC spring and driven the AFC plunger inboard to permit flow through the AFC ducting: this increases the flow area to the rail. Fuel from the AFC circuitry is ducted through the shutdown solenoid and out to the rail pipe.

High speed governing Accelerator is in the full fuel position Supply pressure is higher due to the increased RPM Fuel enters the governor assembly through the governor barrel supply port - but now centrifuge exacted by the flyweights has driven the governor plunger inboard to the extent that the main passage flow area is diminished. More fuel is being spilled by-passing through the centre and cross drillings acting on the governor button to enter the bypass circuit. For the engine to be run in this condition, the accelerator would necessarily be fully depressed, allowing the throttle shaft fuel orifice full register with the main passage. Fuel from the throttle assembly flows to the AFC circuitry. However, until the rpm penetrates well into the droop curve, the engine will be sufficiently fuelled to generate enough rejected heat to ensure that the turbocharger can maintain manifold boost in excess of 15 psi (105kpa). This permits at least some flow through the AFC ducting. Complete high speed governing Engine is being run above the peak speed of the droop curve, beyond high idle. Supply pressure is at maximum.

Fuel enters the governor barrel through the supply port in the governor barrel. In this running condition, the governor flyweights are maximally extended and have driven the governor plunger inboard against the governor spring (high speed spring) to the extent that the main passage has been entirely or almost entirely taken out of register with the recessed plunger annulus The plunger has been driven inboard to the extent that a transverse drilling through the plunger has extended beyond the governor barrel allowing most of the supply fuel to be spilled directly to the bypass. The rpm at which complete high speed governing occurs is determined by the spring tension of the governor (high idle) spring, which is set by shims. At complete high speed governing, so little fuel is being injected into the engine's cylinders, that manifold boost will drop below the 15 psi required to hold the AFC ducting open. So all of the fuel that exits the P.T. pump to the rail must do so by passing around the no-air set screw.

Throttle Shaft System The idle port (or drilling), which allows fuel to flow during low speed operation, and the throttle port, through which fuel flows during times of higher speeds or loads. Whether or not fuel is routed through these two other passages is controlled by just how they are aligned with fuel from the governor plunger, and how hard it is for the fuel volume to push the governor button plunger surface away from the end of the governor plunger. The

throttle shaft system then does the following: 1. Forms the idle fuel passageway 2. Controls fuel flow for selecting the desired engine speed 3. Controls minimum circulation to the injectors (throttle leakage)

Idle passage. Idle fuel flow is controlled by the pump governor. The throttle shaft idle passage is always open to fuel pressure. Manual fuel control passage. Fuel for engine operation must pass through the throttle shaft, which is aligned at this time with the passage in the pump body. Rotation of the throttle shaft causes misalignment of fuel passages and restricts fuel flow, thereby reducing fuel manifold pressure available to the injectors. Two throttle stop screws limit throttle movement. The rear screw allows adjustment of maximum fuel passage opening. The forward screw limits the closed throttle position. On AFC fuel pumps the front throttle stop screw is for throttle travel adjustments and

the rear screw is for throttle leakage adjustments. Throttle leakage. Adjustment of the forward throttle stop screw sets the engine idle speed by controlling the amount of fuel flowing to the injectors with a closed throttle. This throttle leakage also does the following: a. Maintains fuel manifold rail pressure required at the injector metering orifice for immediate acceleration when desired b. Purges air and gases from the injector c. Lubricates the injector Remember that the amount of fuel that will be delivered to the injectors at an idle speed through the idle fuel passage is controlled by the idle spring plunger fuel pump button resting against the governor fuel control plunger in its barrel. This is in turn controlled by the idle spring tension on the back side of the button, while the fuel plunger is pushed against the button by the forces of the weight assist plunger and centrifugal forces developed by the rotating governor weights at the opposite end. When a state of balance is achieved between these opposing forces, a steady fuel pressure and flow rate through the idle fuel passage, as well as throttle leakage, will maintain a steady predetermined idle speed of the engine. A plunger button with too large a number allows the fuel pressure to act on a larger area; this will reduce the pressure at which fuel begins bypassing, thereby lowering the system supply pressure. Alternatively, using a smaller button number than recommended will result in fuel bypassing at a higher pressure, thereby raising the supply pressure. In all truck engine PT fuel pumps the fuel delivered to the injectors (rail pressure) is controlled by use of a selected idle spring plunger button. Sizes increase in increments of 5mm Therefore, when an engine seems to be lacking power, and all possible areas have been checked out to satisfaction, be certain that the correct idle spring plunger button size is being used, since either too small or too large a fuel pump button can drastically alter the fuel rail pressure, and therefore the power output of the engine. Engines will use less fuel per stroke at higher engine RPMs but more fuel is consumed per hour since there are more strokes per unit of time.