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| Illustration 1 | g00757805 |
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Typical example of a basic fuel system diagram (1) Fuel return line from fuel injection pump to fuel filter base (2) Fuel line to fuel injection pump (3) Fuel supply line from fuel filter base to fuel injection pump (4) Fuel filter base (5) Fuel line from fuel transfer pump to fuel filter base (6) Fuel transfer pump (7) Fuel line from fuel tank to fuel transfer pump (8) High pressure fuel line to fuel injection nozzles (9) Fuel injection pump (10) Fuel return line from fuel injection nozzles to fuel filter base (11) Fuel injection nozzle (12) Fuel return line from fuel filter base to fuel tank (13) Fuel tank | |
While the engine is running, fuel is pulled from fuel tank (13) by fuel transfer pump (6). Fuel transfer pump (6) sends the fuel at a low pressure to fuel filter base (4). The fuel then passes through fuel supply line (3) to fuel injection pump (9). Fuel injection pump (9) sends fuel through high pressure fuel lines (8) to each fuel injection nozzle (11). Fuel injection nozzle (11) sprays fuel into the cylinder. The fuel that is not used by the fuel injection nozzles passes through fuel return line (1) from the fuel injection pump to fuel filter base (4). The fuel is then sent back to the fuel injection pump through fuel line (10).
Leakage from fuel injection nozzle (11) flows through fuel return line (10) into the top of fuel filter base (4). The fuel then returns to fuel tank (13) through fuel return line (12).
Fuel injection pump (9) uses fuel for lubrication. Fuel is supplied to the fuel injection pump through fuel line (2) and the fuel is returned to the fuel filter base through fuel return line (1). The precision parts of the fuel injection pump are easily damaged. Therefore, the engine must not be started until fuel injection pump (9) is full of fuel that is free of air.
The system must be primed when any part of the system is drained of fuel for the following reasons:
- The fuel filter is replaced.
- A fuel line is removed.
- The inspection cover on the fuel injection pump is removed for service or repair.
Refer to the Systems Operation, Testing and Adjusting Module, "Fuel System - Prime" topic for the correct procedure.
There is a small screen in fuel transfer pump (6). The fuel transfer pump also has a manual lever that is used to prime the fuel system. There is a banjo bolt on the front of fuel filter base (4) that is used to release air in the system.
An air inlet heater is installed in the inlet manifold. The air inlet heater is controlled by a remote mounted control switch.
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Ensure that there is fuel flow through the valve body of the cold start heater, or damage may occur. The fuel supply line to the inlet air heater must also be free of air, or damage may occur. An inlet air heater that is damaged will let fuel drain into the inlet manifold when the engine is running and could cause exhaust smoke. |
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| Illustration 2 | g00296969 |
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Typical example of a fuel injection nozzle (1) Fuel return (2) Cap nut (3) Fuel inlet (4) Pressure adjusting screw (5) Pressure spring (6) Body (7) Spindle for spring (8) Retaining nut for the nozzle (9) Needle valve (10) Nozzle (11) Orifices (12) Sealing washer | |
Fuel that is under high pressure from the fuel injection pump flows through the orifice in fuel inlet (3). The fuel flows around needle valve (9) and into nozzle (10). The fuel applies pressure against needle valve (9) and pressure spring (5). When the force of the fuel pressure is greater than the force of pressure spring (5), needle valve (9) will raise. Fuel under high pressure will pass through orifices (11) into the cylinder. The force that is created by the pressure of the fuel then becomes less than pressure spring (5) and needle valve (9) will move quickly to the closed position.
Needle valve (9) has a close fit with the inside of nozzle (10). This fit creates a positive seal for needle valve (9).
When the fuel is sent into the cylinder, a small quantity of the fuel will leak past the valve guide. This fuel provides lubrication to the moving parts of the fuel injection nozzle. The fuel then passes through a leak off passage in body (6) to fuel return (1) to the fuel tank.
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| Illustration 3 | g00531642 |
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Typical example of the fuel injection pump components (1) Control lever (2) Flyweights (3) Flow adjusting screw (4) Drive shaft (5) Governor lever (6) Solenoid (7) Housing for delivery valves (8) Control sleeve (9) Feed pump (10) Holder for roller (11) Plunger (12) Cam disk (13) Timer (14) Plunger spring (15) Delivery valve | |
The fuel injection pump is fully closed and pressurized. The fuel injection pump sends the correct amount of high pressure fuel through the fuel injection nozzles to the individual cylinders at the correct time. The correct time is near the end of the compression stroke. The fuel injection pump measures the amount of fuel that is delivered to the fuel injection nozzles. The amount of fuel is controlled by adjusting the governor setting, the position of the accelerator, or the throttle control.
The fuel lines to the fuel injection nozzles are equal lengths. Fuel lines that are equal length ensure even pressure and the correct injection timing at each fuel injection nozzle.
During operation, excess fuel is used for cooling and lubrication. The fuel flows through the housing of the fuel injection pump and back to the fuel tank. Return lines also carry away air that is trapped in the fuel injection nozzles or in the housing of the fuel injection pump.
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| Illustration 4 | g00531644 |
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Typical example of a cross section view of a fuel injection pump (4) Drive shaft (6) Solenoid (8) Control sleeve (12) Cam disk (14) Plunger spring (15) Delivery valve (16) Gear | |
Cam disk (12) is driven from the engine by gear (16). Cam disk (12) is attached to plunger (11) that has dual motion. The lobes on cam disk (12) cause the plunger to reciprocate. The reciprocating motion pressurizes the fuel. This reciprocating motion brings the fuel into the fuel injection pump. Plunger (11) rotates with cam disk (12). This aligns the discharge grooves with each one of the four injection ports on the body of the fuel injection pump. The grooves are aligned in a successive order with the injection ports.
The lobes of the cam determine the travel distance of plunger (11). The effective stroke is determined by the position of control sleeve (8). Moving control sleeve (8) to the left opens the spill port prior to injection. This reduces the amount of fuel that is delivered. Moving control sleeve (8) to the right blocks the spill port. This increases the amount of fuel that is delivered.
The fuel injection pump has a timer (13) that initiates early injection. This is done by advancing the plunger carrier assembly in relation to the cam plate. This occurs while the engine is operating at high speed.
Solenoid (6) is normally closed. When a voltage is applied, the plunger in solenoid (6) moves downward. The plunger prevents the delivery of fuel which causes the engine to stop.
Fuel is drawn from the fuel tank by the fuel transfer pump. The fuel transfer pump pushes the fuel to the fuel filter base and into the fuel filter. The fuel then flows into the inlet of the fuel injection pump through the inlet filter screen. The fuel is drawn by a fuel transfer pump in the fuel injection pump. A portion of the fuel is routed through the pressure regulator assembly to the suction side of the fuel injection pump.
The fuel that is under pressure from the fuel transfer pump flows through the center of the fuel transfer pump rotor, past the rotor retainers, and into a circular groove on the rotor. The fuel flows through a connecting passage in the head into the automatic advance. The fuel flows upward through a radial passage. The fuel passes through a connecting passage to the metering valve. The radial position of the metering valve is controlled by the governor. This regulates the flow of the fuel into the radial charging passage which incorporates the head charging ports.
The two rotor inlet passages register with the charging ports in the hydraulic head as the rotor revolves. This allows fuel to flow into the pumping chamber. The discharge port of the rotor aligns with one outlet of the head as the rotor revolves further. While the discharge port is opened, the rollers contact the lobes of the cam which forces the plungers together. The fuel between the plungers is under pressure. The fuel is then delivered to the cylinder through the fuel injection nozzle.
The fuel injection pump is self-lubricating. The fuel that is at pressure from the fuel transfer pump reaches the charging ports. The slots on the rotor shank allow fuel and any air that is trapped to flow into the cavity of the fuel transfer pump housing.
An air vent passage in the hydraulic head connects the outlet side of the fuel transfer pump with the housing of the fuel injection pump. This allows air and some of the fuel to flow back to the fuel tank through the fuel return line. The fuel that flows into the housing of the fuel injection pump performs the following functions:
- Lubricate the internal components.
- Cool the internal components.
- Remove small air bubbles.
The housing of the fuel injection pump is full of fuel while the fuel injection pump is operating. There are no dead air spaces within the fuel injection pump.
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| Illustration 5 | g00657973 |
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Typical example (1) Fuel line to heater (2) Air inlet heater | |
The engine is equipped with an air inlet heater (2). Air inlet heater (2) is installed in the air inlet manifold in order to heat the inlet air in cold weather conditions.
The current that flows through the coil in air inlet heater (2) will cause the coil to become hot under the following conditions:
- The ignition switch is turned to the position for heating.
- The control switch is pushed in and the fuel shutoff control is on.
A small amount of fuel will flow through the fuel line to air inlet heater (2) when the engine is cranking.
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| Illustration 6 | g00531702 |
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Air inlet heater (3) Fuel inlet (4) Ball valve (5) Valve body (6) Coil | |
Valve body (5) is heated. Valve body (5) expands. This allows ball valve (4) to open. The fuel flows into valve body (5) from fuel inlet (3).
The fuel is turned into a vapor by the heat of valve body (5). Air is brought into the inlet manifold while the engine is cranking. The vapor is ignited by coil (6) and burns. This heats the inlet air.