Fuel System Description. Chevrolet Chevy P42 Commercial Chassis 1999

For 1990-2009 cars only

Makes 🢒 Chevrolet 🢒 1999 🢒 Chevy P42 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 6.5L (L57) 🢒 Fuel System Description

Fuel System Description EFI

The fuel injection system has a PCM controlled fuel injection pump mounted on top of the engine under the intake manifold. The pump is driven by the camshaft through two gears, one attached to the front of the camshaft and the other attached to the end of the pump shaft. These gears are the same size and have the same number of teeth; therefore, the injection pump shaft turns at the same speed as the camshaft.

Electronic Fuel Injection Pump


(1)	Fuel Solenoid Driver
(2)	Optical/Fuel Temperature Sensor
(3)	Fuel Inlet
(4)	Engine Shutoff Solenoid
(5)	Two Stage Housing Pressure Regulator
(6)	Injector Timing Stepper Motor
(7)	Fuel Solenoid

The injection pump is a high pressure rotary type that is controlled by the PCM. The injection pump meters, pressurizes, and distributes fuel to the eight injector nozzles by way of eight high pressure lines. An outlet port in the injection pump allows the fuel to enter the fuel return system and then travel back to the fuel tank.

Injection Nozzles


(1)	Inlet
(2)	Return
(3)	Pressure Spring
(4)	Nozzle Nut
(5)	Needle Valve
(6)	Pintle

Each cylinder has an identical fuel injection nozzle mounted in the pre-combustion chamber. As the pressure wave of injection reaches a nozzle, the needle valve is lifted against spring force and fuel exits into the pre-combustion chamber of the cylinder as a highly atomized spray. A small amount of fuel travels between the needle valve and pintle nozzle, providing lubrication. Two passages inside the upper half of the nozzle body allow fuel that has lubricated the needle valve to exit into the fuel return system.

Injection Lines


(1)	Cylinder 8
(2)	Cylinder 7
(3)	Cylinder 2
(4)	Cylinder 6
(5)	Cylinder 5
(6)	Cylinder 4
(7)	Cylinder 3
(8)	Cylinder 1

The injection lines connect the high pressure discharge fittings on the head of the injection pump to the injection nozzles. The injection lines are pre-bent for correct routing and connect to the injection pump head as shown in the figure above. The injection lines are equal in length and interior volume.

Fuel Metering

The fuel metering is accomplished by the fuel solenoid driver by using the signals from the PCM in order to control the fuel injection solenoid.

Injection Timing

The injection timing stepper motor advances or retards the injection timing by the signals that are received from the PCM.

Engine Shutoff Solenoid

When not activated by the PCM, the engine shutoff solenoid blocks the fuel flow from entering the transfer pump inside of the injection pump and stops the engine operation.

Accelerator Control System

The accelerator control system is an electronically controlled throttle type with an accelerator pedal attached to an accelerator pedal position module (2). This module sends the signals to the PCM which then controls the fuel injection pump.

Fuel System Description MFI

The fuel injection system has a mechanical fuel injection pump mounted on top of the engine under the intake manifold. The pump is driven by the camshaft through two gears, one attached to the front of the camshaft and the other attached to the end of the pump shaft. These gears are the same size and have the same number of teeth; therefore, the injection pump shaft turns at the same speed as the camshaft.

Mechanical Fuel Injection Pump

The injection pump is a high pressure rotary type. The injection pump meters, pressurizes, and distributes fuel to the eight injector nozzles by way of eight high pressure lines. An outlet port in the injection pump allows the fuel to enter the fuel return system and then travel back to the fuel tank. The function of the fuel injection pump is to meter the fuel according to engine power requirements and to inject the fuel at high pressure through nozzles into the combustion chambers of the engine at the correct timing intervals

Injection Nozzles


(1)	Inlet
(2)	Return
(3)	Pressure Spring
(4)	Nozzle Nut
(5)	Needle Valve
(6)	Pintle

The main purpose of the nozzles are to direct and to atomize the metered fuel into the pre-combustion chamber. Each cylinder has an identical fuel injection nozzle mounted in the pre-combustion chamber. As the pressure wave of injection reaches a nozzle, the needle valve is lifted against spring force and fuel exits into the pre-combustion chamber of the cylinder as a highly atomized spray. A small amount of fuel travels between the needle valve and pintle nozzle, providing lubrication. Two passages inside the upper half of the nozzle body allow fuel that has lubricated the needle valve to exit into the fuel return system.

Injection Lines


(1)	Cylinder 8
(2)	Cylinder 7
(3)	Cylinder 2
(4)	Cylinder 6
(5)	Cylinder 5
(6)	Cylinder 4
(7)	Cylinder 3
(8)	Cylinder 1

Injection Timing (Advance Systems)

Timing advance is needed to compensate for two delay periods:

•	the injection pressure wave

•	the ignition delay period

The injection timing advance system controls the start of injection proportional to pump speed. This is done by moving the cam ring (located in the fuel injection pump) opposite the direction of the rotor rotations. Secondary control of the cam ring advance is by a mechanical connection from the throttle shaft through a face cam and a rocker lever to the servo advance piston valve seat. The secondary timing control results in injection timing better suited to engine demand.

Housing Pressure Cold Advance (HPCA)

The injection pump is equipped with a HPCA solenoid. This component will allow more advance during engine warm up. The electrical signal which controls the operation of the solenoid is generated by the cold advance circuit relay. The switch is calibrated to open at 115°F (46°C). Below the switch point, housing pressure is decreased from 8 - 12 psi to zero which advances the timing to 3°.

Fast Idle Solenoid

The fast idle solenoid is energized by the cold advance circuit relay. The fast idle solenoid operates at the same time the HPCA is engaged.

Engine Shutoff Solenoid

When the ESO solenoid is de-energized, an arm on the solenoid is moved out by spring force and physically closes the metering valve. This action interrupts injection, and stops the engine.