Diesel MFI Pump: Description and Operation

Electronic Fuel Injection Pump:

DESCRIPTION
The injection pump is a high pressure rotary type pump that is controlled by the Powertrain Control Module (PCM) and 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 fuel to enter the fuel return system and travel back to the fuel tank.

Fuel Metering
Fuel metering is accomplished by the fuel solenoid driver using signals from the PCM to control the fuel injection solenoid.

Injection Timing
The injection timing stepper motor advances or retards injection timing by signals received from the PCM.

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

Injection Lines
The high-pressure discharge fittings on the head of the injection pump connect to the injection nozzles with steel lines of equal length and interior volume.

When the engine is not running, fuel is contained in the injection lines. During engine operation, a residual pressure of approximately 500 psi is maintained in each injection line. As injection occurs in each line, a small amount of fuel enters the line, pushing a similar amount into the nozzle at the other end with a pressure wave.