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| Illustration 1 | g00849199 |
Diagram of the basic fuel system (typical example) (1) Fuel injection nozzle (2) Fuel return line from fuel injection nozzle (3) Air inlet heater (4) Fuel return line from fuel filter (5) Fuel return line from fuel injection pump (6) Fuel supply line (7) Fuel filter (8) Fuel transfer pump (9) Water separator (10) Fuel injection pump (11) High pressure fuel lines (12) Fuel tank | |
When the engine is cranking, the fuel is pulled from fuel tank (12) through water separator (9) by fuel transfer pump (8). When the fuel goes through the water separator, any water in the fuel will go to the bottom of the bowl. The fuel transfer pump sends the fuel at a low pressure to fuel filter (7). From the fuel filter, the fuel goes through fuel supply line (6) to fuel injection pump (10) .
The fuel injection pump sends fuel through high pressure fuel lines (11) to each of fuel injection nozzles (1). The fuel injection nozzle sprays fuel into the cylinder. Fuel which is not used by the fuel injection pump goes through fuel return line (5) to the inlet side of fuel filter (7). Leakage from the fuel injection nozzles flows through the fuel return line from fuel injection nozzle (2) to the top of fuel filter (7), back to fuel tank (12), and through the fuel return line from fuel filter (4) .
The fuel injection pump needs fuel for lubrication. The precision parts of the pump are easily damaged. For this reason, the engine must not be started until the fuel injection pump is full of fuel that is free of air.
The system must be primed when any part of the system is drained of fuel. The following list contains examples of both service and repairs when you must prime the system:
- The fuel filter is changed.
- The fuel line is removed.
- The fuel injection pump is removed.
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| Illustration 2 | g00845968 |
Fuel system components (left side) (1) Fuel injection nozzle (2) Fuel return line from fuel injection nozzle (3) Air inlet heater (7) Fuel filter (10) Fuel injection pump (11) High pressure fuel lines (13) Fuel filter base (14) Fuel return line (15) Fuel supply line for the air inlet heater | |
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| Illustration 3 | g00845981 |
Fuel system components (right side) (8) Fuel transfer pump | |
There is a small filter screen in fuel transfer pump (8). The pump has a lever which is manually operated in order to prime the fuel system by removing the air. In order to release air from the system, the orifice in the cover of fuel filter (7) is in the inlet side of the filter. The orifice is connected to the fuel tank by the fuel return line from fuel filter (7).
| NOTICE |
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If there is no fuel flow through the valve body of the air inlet heater, the fuel injection pump could be damaged. The fuel supply line to the air inlet heater must also be free of air in order to prevent damage. |
| NOTICE |
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An air inlet heater that is damaged will allow the fuel to drain into the inlet manifold when the engine is running. This condition could cause exhaust smoke. Excessive fuel could also cause an overspeed condition. An overspeed condition may result in severe engine damage. |
The air inlet heater is an electrically operated device. The air inlet heater ignites a controlled amount of diesel fuel in the inlet manifold in order to heat the inlet air. A heater coil in the air inlet heater expands a delivery valve holder in order to allow the fuel to flow into the heater. The fuel is ignited by the hot coil. The combustion heats the air which passes through the inlet manifold when the starter motor is operated.
Air inlet heater (3) is installed in the inlet manifold. The air inlet heater is controlled by a remote mounted control switch.
Fuel Injection Nozzles
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| Illustration 4 | g00849625 |
Fuel injection nozzle (1) Fuel inlet (2) Fuel return line (3) Holder for the fuel injection nozzle (4) Fuel injection nozzle (5) Seat washer (6) Orifices | |
Note: This fuel injection nozzle is not serviceable.
Each fuel injection nozzle is fastened to the cylinder head by a gland nut on the holder for fuel injection nozzle (3). Fuel injection nozzles are not serviceable except for removal of fuel injection nozzle (4) in order to clean the orifice (6) .
The operating pressure of the fuel injection nozzle is set and tested at the factory. Refer to Specifications, "Fuel Injection Nozzles" for the pressure settings of the fuel injection nozzles.
The fuel injection pump forces the fuel to flow under high pressure to the hole in fuel inlet (1). The fuel then flows around a needle valve within fuel injector holder (3) which causes fuel injection nozzle (4) to fill with fuel. The pressure of the fuel pushes the needle valve and a spring. When the force of the fuel pressure is greater than the force of the spring, the needle valve will lift up.
When the needle valve opens, fuel under high pressure will flow through nozzle orifices (6) into the cylinder. The fuel is injected into the cylinder through the orifices in the nozzle end as a very fine spray. When the fuel is injected into the cylinder, the force of the fuel pressure in the nozzle body will decrease. The force of the spring will then be greater than the force of the fuel pressure that is in the nozzle body. The needle valve will move quickly to the closed position.
The needle valve has a close fit with the inside of the nozzle. This makes a positive seal for the valve.
When the fuel flows to the cylinder, a small quantity of fuel will leak by the valve guide. This fuel lubricates the moving parts of the fuel injection nozzle. This fuel then goes through a passage in the holder for fuel injection nozzle (3) to fuel return line (2). This excess fuel is then returned to the fuel tank.
Fuel Injection Pump
General Operation
The fuel injection pump is a pressurized system that is totally enclosed. The pump sends the correct amount of fuel under high pressure at the correct time through the fuel injection nozzles to the individual cylinders. The correct timing occurs near the end of the compression stroke. The fuel injection pump regulates the amount of fuel that is delivered to the fuel injection nozzles. This action controls the engine rpm by the governor setting or the position of the throttle control.
The fuel lines to the fuel injection nozzles are equal lengths. This ensures even pressure and correct injection timing at each fuel injection nozzle.
During operation, extra fuel is used as coolant and lubricant for pump parts that move. The extra fuel is circulated through the pump housing. The extra fuel is then returned to the fuel tank. Fuel return lines also carry away any air that is trapped in the fuel injection nozzles or the fuel injection pump housing.
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| Illustration 5 | g00296973 |
Diagram of the operation of a fuel injection pump (1) Drive shaft (2) Gear (3) Control sleeve (4) Solenoid (5) Cam (6) Plunger spring (7) Plunger (8) Delivery valve | |
The fuel injection pump transfers fuel to the fuel injection nozzles at high pressure. Cam (5) is driven from the engine by gear (2). Lobes on cam (5) cause the plunger to reciprocate. The reciprocating motion first draws the fuel. The reciprocating motion then pressurizes the fuel.
Plunger (7) also rotates with cam (5) in order to sequentially align the discharge groove of the cam with each of the ports on the fuel injector pump. Plunger (7) moves a distance which is established by the lobes of the cam.
The effective stroke is established by the position of the control sleeve. When control sleeve (3) is moved to the left prior to the injection of fuel, the spill port is uncovered. Uncovering the spill port reduces the amount of fuel that is delivered to the cylinder. When control sleeve (3) is moved to the right prior to the injection of fuel, the spill port is covered. Covering the spill port increases the amount of fuel that is delivered to the fuel injection nozzle.
The pump also includes an internal timer (not shown). The timer allows early fuel injection by advancing plunger (7). The plunger is advanced in relation to the camshaft. Solenoid (4) is normally closed. When the voltage is applied, plunger (7) moves in order to block the fuel delivery which stops the engine.
Fuel Flow
The fuel injection pump pumps the fuel from the fuel tank through filters. The fuel flows through the center of the rotor of the injection pump into a circular groove on the rotor. The fuel then flows to the automatic advance and through a connecting passage to the metering valve. The radial position of the metering valve is controlled by the governor.
The metering valve regulates the flow of the fuel to the discharge ports. When the rotor revolves, the two inlet passages of the rotor match up to the discharge ports which are located in the hydraulic head. The discharge ports allow the fuel to flow into the pumping chamber. When the rotor rotates further, the discharge port of the rotor matches up with one of the outlets of the hydraulic head. When the discharge port is opened, the rollers contact the lobes of the cam which forces the plungers together. Fuel that is trapped between the plungers is then pressurized. Then, the fuel flows to the fuel injection nozzle. The fuel injection nozzle delivers the fuel to the cylinder.
When fuel reaches the discharge ports, slots on the rotor allow the fuel and any air which is entrapped to flow into the cavity of the pump housing. A passage in the hydraulic head connects the outlet side of the transfer pump with the pump housing. This passage vents the air from the fuel injection pump through the fuel return line. This passage also allows some fuel to leak back to the fuel tank through the fuel return line.
The fuel which leaks back to the fuel tank performs the following function before being discharged through the fuel return line.
- The housing is filled with fuel, which helps prevent any buildup of air.
- The internal components are lubricated.
- The fuel injection pump is cooled.
- Small air bubbles are removed.
When the fuel injection pump is operating normally, the housing must be completely full of fuel. The fuel injection pump is self-lubricating.
Operation of the Stanadyne Fuel Injection Pump and the Delphi Fuel Injection Pump
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| Illustration 6 | g00298860 |
Fuel injection pump components (typical example) (1) Drive shaft (2) Bushing of the drive shaft (3) Governor flyweights (4) Governor (5) Internal cam ring (6) Rollers (7) Metering valve (8) Discharge fitting (9) Transfer pump (10) Pressure regulator (11) Housing (12) Timing advance (13) Plungers (14) Hydraulic head (15) Delivery valve (16) Distributor rotor | |
The main rotating components are drive shaft (1), distributor rotor (16), transfer pump (9) and governor (4). Drive shaft (1) engages the distributor rotor (16) in hydraulic head (14). The drive end of distributor rotor (16) has two or four plungers (13). Plungers (13) are moved toward each other simultaneously by an internal cam ring (5) through rollers (6) and shoes. The rollers and shoes are positioned in slots at the drive end of distributor rotor (16) .
Transfer pump (9) is located at the rear of distributor rotor (16) in the end cap. The end cap also contains the strainer for the fuel inlet and pressure regulator (10) for the transfer pump. The transfer pump has a positive displacement vane. The pressure that is generated by the transfer pump is automatically compensated for the effects of viscosity due to temperature changes and fuel grades. Distributor rotor (16) has a single axial bore with the following passages:
- Two charging ports
- One discharge port
The single discharge port serves all of the head outlets to the fuel injection lines. Hydraulic head (14) consists of the following parts:
- The bore for the rotor
- The bore for metering valve (7)
- The charging ports
- Discharge fittings (8) of the head
The high pressure fuel lines to the fuel injection nozzles are fastened to these discharge fittings (8). The fuel injection pump contains a mechanical governor (4). The centrifugal force of the governor flyweights (3) that are in the retainer is transferred through the following items: a sleeve to the governor arm, linkage and metering valve (7). Timing advance (12) is a hydraulic mechanism. The timing advance unit performs one of the following functions:
- Advance the delivery of fuel.
- Retard the delivery of fuel.
An electrical stop solenoid is contained inside the governor housing. The electrical ground is on top of the governor housing. The supply connections are on the top of the governor housing. When the voltage is applied, the plunger of the solenoid moves in order to block the flow of fuel to the engine. When the fuel flow is stopped, the engine stops.
Operation of the Bosch Fuel Injection Pump
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| Illustration 7 | g00556681 |
Fuel injection pump components (Bosch) (1) Control lever (2) Flyweights (3) Screw for adjusting the full load setting (4) Drive shaft (5) Governor lever (6) Solenoid (7) Head of the distributor (8) Control sleeve (9) Transfer pump (10) Holder for the rollers (11) Plunger (12) Cam (13) Timer (14) Plunger spring (15) Delivery valve | |
The operation of the Bosch fuel injection pump is similar to the operation of the Stanadyne fuel injection pump.
Components of the Bosch Fuel Injection Pump
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| Illustration 8 | g00849298 |
Fuel injection pump components (Bosch) (1) Fuel return line (2) Low idle speed adjustment (3) High idle speed adjustment (4) Fuel supply connection (5) Electrical connection for the stop solenoid (6) High pressure fuel line connection (7) Flange nut (8) Discharge fitting | |
The internal adjustment for the pump timing is tamper proof. The low idle is adjustable.
The Bosch fuel injection pump is installed on the naturally aspirated engine and the turbocharged engine. Engines with turbochargers are installed with a boost control. The boost control is a device that is regulated by boost pressure from the turbocharger. The boost control reduces the maximum fuel delivery at lower engine rpm in order to match the reduced air supply to the combustion chamber.
Note: For a basic description of the operation of the fuel injection pump, please refer to the Systems Operation Module, "Fuel System: Fuel Injection Pump" for more information.
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| Illustration 9 | g00849561 |
Cold starting aid (Bosch) (9) Electrical connection (10) Lever for pump timing (11) Body | |
The fuel injection pump has an electrically operated cold starting aid which holds the timing of the pump in an advanced position when the engine is cold. The cold starting aid is connected by a shaft to the advance lever for the timing of the fuel injection pump.
A temperature switch is installed in the coolant passage which is located at the rear of the timing case. The temperature switch sends current to electrical connection (1) of the cold starting aid when the engine is started and when the engine is below normal operating temperature. The body (3) contains a wire coil with high electrical resistance. The wire coil surrounds an element which is filled with wax. The wire coil heats the wax which then expands. The expansion of the wax forces a rod to move lever (2) of the timing advance. The lever continuously adjusts the pump to the correct timing for the normal operating temperature.
Components of the Delphi DP200 Series Fuel Injection Pump
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| Illustration 10 | g00296984 |
Components of the fuel injection pump (Delphi DP200 Series)
(1) O-ring (2) Hub nut (3) Locking spacer (4) Locking screw (5) Low idle adjustment screw (6) High idle adjustment screw (7) Fuel return line connection (8) Electrical connection for stop solenoid (9) Fuel supply connection (10) Mounting flange (11) Connection for the high pressure fuel injector lines (12) Adjustment screw for timing advance (13) Fitting for the fuel discharge line | |
The Delphi fuel injection pump is installed on the naturally aspirated engine and the turbocharged engine.
The internal adjustment for the pump timing is tamper proof. The low idle is adjustable. The fuel injection pump has a boost control and an engine stop solenoid. The pump also has a self-vent feature which removes air from the pump.
The fuel injection pump has an electrically operated cold starting aid which holds the timing of the pump in an advanced position when the engine is cold. The advance lever of the pump is enclosed within the pump housing.
The cold starting aid is connected by a shaft to the advance lever for the timing of the fuel injection pump. The lever that is used to advance the pump timing is an internal component of the fuel injection pump. The cold starting aid is an internal component of the fuel injection pump and the cold starting aid is not adjustable.
A coolant temperature switch is installed in the coolant passage that is located at the rear of the timing case. The temperature switch sends current to electrical connection (12) of the cold starting aid when the engine is started and when the engine is below normal operating temperature. The body contains a wire coil with high electrical resistance. The wire coil surrounds an element which is filled with wax. The wire coil heats the wax which then expands. The expansion of the wax forces a rod to move the lever of the timing advance. The lever continuously adjusts the pump to the correct timing for the normal operating temperature.
Note: For a basic description of the operation of the fuel injection pump, please refer to the Systems Operation Module, "Fuel System: Fuel Injection Pump" for more information.
Components of the Stanadyne Fuel Injection Pump
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| Illustration 11 | g00849294 |
Components of the fuel injection pump (Stanadyne) (1) Electrical connection for stop solenoid (2) Connection for fuel return line (3) Low idle adjustment screw (4) High idle speed adjustment screw (5) Flange nut (6) Nut for end cap (7) Fitting for fuel discharge (8) High pressure fuel injection lines (9) Adjustment screw for timing advance | |
The Stanadyne fuel injection pump is installed on the naturally aspirated engine and the turbocharged engine.
The internal adjustment for the pump timing is tamper proof. The low idle is adjustable. The fuel injection pump has a boost control and an engine stop solenoid. The pump also has a self-vent feature which removes air from the pump.
The fuel injection pump has an electrically operated cold starting aid which holds the timing of the pump in an advanced position when the engine is cold. The advance lever of the pump is enclosed within the pump housing.
The cold starting aid is connected by a shaft to the advance lever for the timing of the fuel injection pump. The cold starting aid and the advance lever are internal components of the Stanadyne fuel injection pump. The cold starting aid is not adjustable.
A temperature switch is installed in the coolant passage which is located at the rear of the timing case. The temperature switch sends current to the electrical connection (9) of the cold starting aid (not shown) when the engine is started and when the engine is below normal operating temperature. The body contains a wire coil with high electrical resistance. The wire coil surrounds an element which is filled with wax. The wire coil heats the wax which then expands. The expansion of the wax forces a rod to move the lever of the timing advance. The lever continuously adjusts the pump to the correct timing for the normal operating temperature.
Note: For a basic description of the operation of the fuel injection pump, please refer to the Systems Operation Module, "Fuel System: Fuel Injection Pump" for more information.
Air Inlet Heater
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| Illustration 12 | g00849290 |
Location of the air inlet heater (1) Air inlet heater (2) Fuel line | |
The engine is equipped with an air inlet heater (1). The air inlet heater is installed in the inlet manifold in order to heat the intake air in cold weather.
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| Illustration 13 | g00642969 |
Air inlet heater (3) Electrical connection (4) Fuel inlet (5) Ball valve (6) Delivery valve holder (7) Wire coil (8) Ignition coil | |
When the ignition switch is turned to the HEAT position or when the control switch is pushed and the fuel shutoff control is in the ON position, electrical current is supplied to electrical connection (3). The electrical current flows to wire coil (7) which causes the wire coil to become very hot. A small amount of fuel will flow through the fuel line when the engine is cranking.
The air inlet heater ignites a controlled amount of diesel fuel in the intake manifold in order to heat the intake air to the engine. The air inlet heater uses electric current to cause a heater coil in the body to create heat. The heat causes the expansion of a delivery valve holder (6) which opens ball valve (5) in order to allow the fuel to flow into the air inlet heater.
The fuel is vaporized by the heat of the valve body. When the engine is cranked, the air is forced into the inlet manifold. The vapor is ignited by ignition coil (8). The heat from the combustion of the fuel heats the intake air.
When the ignition switch is turned to RUN position or the control switch is released, electric current stops to the cold starting aid. When the engine begins to run, the flow of air in the inlet manifold makes the cold starting aid cool quickly. The valve closes. This stops the fuel flow in the fuel supply line.
If the engine does not start after twenty seconds, turn the ignition switch to the HEAT position or push the control switch for ten seconds. Then crank the engine.