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| Illustration 1 | g00533409 |
Fuel System Schematic (1) Fuel priming pump (2) Fuel injection pump housing (3) Fuel injection line (4) Check valve (5) Fuel injector nozzle (6) Secondary fuel filter (7) Fuel return line (8) Fuel transfer pump (9) Primary fuel filter (10) Fuel tank (11) Electronic Control Module | |
As the engine is being cranked and started, the fuel transfer pump (8) pulls fuel from fuel tank (10) through the primary fuel filter (9) .
Note: When the engine has reached normal operating temperature, the inlet fuel temperature to the transfer pump must not exceed 65 °C (149 °F). Fuel temperatures above 65 °C (149 °F) reduce the life of the electronics in the ECM and the transfer pump check valves. High fuel temperatures also reduce the engine's power output. Make sure that the fuel heaters are turned OFF in warm weather operating conditions.
After the fuel transfer pump (8), the fuel is pushed through the ECM (11) in order to stabilize the temperature of the electric circuits. The cooling plate for the ECM is an aluminum die cast housing. Manifolds on the top and the bottom of the ECM route fuel from the transfer pump through the cooling plate.
The fuel exits the ECM and flows through the secondary fuel filter (6) and to the fuel manifold in the fuel injection pump housing (2) .
Fuel pressure in the fuel manifold is determined by the fuel transfer pump spring. A constant bleed orifice is in the fuel return line elbow at the injection pump housing. This orifice allows a continuous flow of fuel to go through the fuel return line (7) and back to the fuel tank (10). This helps keep the fuel cool and free of air. The individual fuel injection pumps get the fuel from the fuel manifold. The fuel injection pumps push the fuel at a very high pressure through the fuel lines (3) and to the fuel injector nozzles (5). Each fuel injector nozzle has very small holes in the tip that change the flow of fuel into a very fine spray. The spray gives good fuel combustion in the cylinder.
Fuel Heaters
Fuel heaters prevent plugging of the fuel filters in cold weather due to waxing of the oil. The PEEC III system does not dissipate enough heat into the fuel in order to prevent the use of fuel heaters. Fuel heaters that are not thermostatically controlled can heat the fuel in excess of 65°C (150°F). High fuel temperatures reduce the following objects:
- the engine's performance
- the life of the transfer pump check valve
- the PEEC III system's reliability
Note: Fuel heaters without thermostatic controls must never be used with the PEEC III system.
Only thermostatically controlled fuel heaters or self-adjusting fuel heaters can be used.
Fuel Transfer Pump
The fuel transfer pump is a piston pump that is moved by a cam on the camshaft in the fuel injection pump. The transfer pump is located on the bottom side of the fuel injection pump housing.
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| Illustration 2 | g00533412 |
Fuel Transfer Pump Start Of Down Stroke Arrows Indicate The Fuel Flow Direction. (1) Push rod (2) Piston (3) Outlet check valve (4) Pump 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 the push rod (1) and the piston (2) downward. As the piston moves down, inlet check valve (7) and outlet check valve (3) close. The pump check valve (4) opens. This allows the fuel that is below the piston to move into the area above the piston. Pumping spring (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). Now, the pumping spring (5) moves the piston (2) upward. 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 area above the piston is pushed through the outlet check valve (3) and out pump outlet port (8). Fuel also moves through the pump inlet port (6) and the inlet check valve (7) in order to fill the area below the piston (2). The pump is now ready to start a new cycle.
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| Illustration 3 | g00533414 |
Fuel Transfer Pump Start Of Up Stroke Arrows Indicate Fuel Flow Direction. (1) Push rod (2) Piston (3) Outlet check valve (4) Pump check valve (5) Pumping spring (6) Pump inlet port (7) Inlet check valve (8) Pump outlet port | |
Fuel Injection Pump
The fuel injection pump increases the pressure of the fuel and the fuel injection pump sends an exact amount of fuel to the fuel injector nozzle. There is one fuel injection pump for each cylinder in the engine.
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| Illustration 4 | g00533415 |
Fuel Injection Pump (1) Spill port (2) Check valve (3) Pump barrel (4) Bypass port (5) Pump plunger (6) Spring (7) Fuel rack (8) Gear (9) Lifter (10) Cam | |
The fuel injection pump is moved by cam (10) of the fuel pump camshaft. When the camshaft turns, the cam raises lifter (9) and the pump plunger (5). The pump plunger always makes a full stroke. As the camshaft turns farther, spring (6) returns the pump plunger and the lifter to the bottom of the stroke.
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| Illustration 5 | g00533417 |
Pump Barrel And Plunger Assembly (1) Spill port (2) Check valve (3) Pump barrel (4) Bypass port (5) Pump plunger (11) Orificed reverse flow check valve (12) Spring (13) Spring (14) Scroll (15) Slot | |
When the pump plunger is at the bottom of the stroke, fuel at transfer pump pressure flows through spill port (1) and bypass port (4). Fuel fills pump barrel (3) in the area above pump plunger (5).
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| Illustration 6 | g00533423 |
Pump Barrel And Plunger Assembly (1) Spill port (2) Check valve (3) Pump barrel (4) Bypass port (5) Pump plunger (11) Orificed reverse flow check valve (12) Spring (13) Spring (14) Scroll (15) Slot | |
After the pump plunger (5) begins the up stroke, the fuel will be pushed out of the bypass port (4) until the top of the pump plunger closes the port. As the pump plunger travels further upward, the pressure of the fuel increases. At approximately 690 kPa (100 psi), the check valve (2) opens. This allows fuel to flow into the fuel injection line to the fuel injector nozzle.
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| Illustration 7 | g00533426 |
Pump Barrel And Plunger Assembly (1) Spill port (2) Check valve (3) Pump barrel (4) Bypass port (5) Pump plunger (11) Orificed reverse flow check valve (12) Spring (13) Spring (14) Scroll (15) Slot | |
When the pump plunger travels further upward, the scroll (14) uncovers the spill port (1). The fuel above the pump plunger goes through the slot (15). The fuel then goes along the edge of the scroll (14). The fuel then goes out of the spill port (1). The fuel then goes back to the fuel manifold. This is the end of the injection stroke. Although the pump plunger can have more travel upward, no more additional quantities of fuel will be sent to the fuel injector nozzle.
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| Illustration 8 | g00533427 |
Pump Barrel And Plunger Assembly (1) Spill port (2) Check valve (3) Pump barrel (4) Bypass port (5) Pump plunger (11) Orificed reverse flow check valve (12) Spring (13) Spring (14) Scroll (15) Slot | |
When spill port (1) is opened by plunger (5) the fuel injector nozzle closes and spring (13) closes check valve (2) as the pressure above plunger (5) drops below 690 kPa (100 psi). At the same time orificed reverse flow check valve (11) opens.
Orificed reverse flow check valve (11) closes when the fuel pressure in the fuel injection lines is 6900 kPa (1000 psi). This keeps the fuel in the injection line and above the reverse flow check valve at 6900 kPa (1000 psi).
Note: Reverse flow check valve (11) prevents rough idle by stopping any secondary injection of fuel between injection strokes. This valve is only effective below 8250 kPa (1200 psi) and the valve has no effect above that pressure. When the engine is shutdown, the pressure is gradually released through a small groove on the bottom face of reverse flow check valve (11).
Fuel begins to fill the area above the pump plunger after the pump plunger travels downward and the pump plunger uncovers the bypass port (4). The pump is ready to begin another stroke.
The amount of fuel that is sent by the injection pump to the fuel injector nozzle on each pump stroke can be changed by rotating the pump plunger. Gear (8) is attached to the pump plunger and the gear is meshed with the fuel rack (7). The ECM moves the fuel rack by using the rack actuator. The fuel rack turns the pump plungers. When the fuel rack turns the pump plunger, the scroll (14) on the plunger changes the distance between the top of pump plunger and the uncovering of the spill port (1). As the distance gets longer, the amount of fuel that gets injected becomes larger.
To stop the engine, the pump plunger is rotated so that slot (15) on the pump plunger is in line with spill port (1). Thus, no fuel is delivered to the fuel injector nozzle.
Fuel Injector Nozzle
The fuel injector nozzle goes through the cylinder head into the combustion chamber. The fuel injection pump sends fuel with high pressure to the fuel injector nozzle. The fuel injector nozzle turns the fuel into a fine spray which is good for combustion.
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| Illustration 9 | g00533429 |
Fuel Injector Nozzle (1) Carbon dam (2) Seal (3) Passage (4) Filter screen (5) Inlet passage (6) Orifice (7) Valve (8) Diameter (9) Spring | |
Seal (2) goes against the nozzle adapter in order to prevent leakage from the cylinder. Carbon dam (1) keeps carbon out of the bore in the nozzle adapter.
Fuel with high pressure from the fuel injection pump goes into inlet passage (5). The fuel then goes through the filter screen (4) and into the passage (3) to the area below the diameter (8) of the valve (7). When the force of the fuel on diameter (8) becomes greater than the force of the spring (9), the valve (7) unseats. This occurs when the fuel pressure goes above the valve opening pressure of the fuel injector nozzle. When valve (7) unseats, the tip of the valve comes off of the nozzle seat and the fuel will go through the six small orifices (6) into the combustion chamber.
The injection of fuel continues until the pressure of fuel against diameter (8) becomes less than the force of spring (9). With less pressure against diameter (8), spring (9) pushes valve (7) against the nozzle seat which stops the flow of fuel into the combustion chamber.
The fuel injector nozzle can not be disassembled and no adjustments can be made.