Fuel Pump: Description and Operation

Fuel Pump Circuit:

Fuel Pump Location:

PURPOSE
The fuel pump supplies the injection pump with fuel from the fuel tank.

OPERATION
The lift pump receives power from two circuits, one while the engine is cranking and the other when the engine is running.
When the ignition switch is moved to the "CRANK" position, the lift pump circuit is completed through the relay contacts. During engine cranking oil pressure increases to the point of closing the contacts of the oil pressure switch/sending unit. A minimum of 28 kPa (4 psi) oil pressure is required to close the switch contacts.
When the engine starts and the ignition is returned to the "RUN" position, the oil pressure of the running engine maintains electrical power to the lift pump through the oil pressure switch/sending unit.
The fuel pump should deliver fuel to the fuel injection pump at a pressure of 40 - 60 kPa (5.8 - 8.7 psi).

CONSTRUCTION
The electrical circuits and components for the lift pump are:
- Oil pressure switch/sending unit.
- Relay.
- In-line fuse.
- Lift pump.


LOCATION
The fuel pump is mounted to the left frame rail under vehicle.