Fuel Pump Relay: Description and Operation

PURPOSE
The relay supplies battery voltage to fuel pump and oxygen sensor heater element when energized by Powertrain Control Module (PCM).

OPERATION
The PCM energizes fuel pump relay by supplying relay ground, when ignition switch is in START or RUN position and PCM is receiving a reference signal from distributor.

When the PCM does not receive reference signal from ignition system, (indicating engine is not running), then the PCM interrupts relay ground circuit and no voltage is supplied to fuel pump, ignition coil, or oxygen sensor heater element.

The PCM controls fuel pump relay and Auto Shutdown (ASD) relay simultaneously, through same ground circuit.

CIRCUIT OPERATION
Circuit A14 from fuse 8 in the Power Distribution Center (PDC) supplies battery voltage to the contact side of the fuel pump relay. Circuit F18 from fuse 9 in the fuse block supplies battery voltage to the coil side of the fuel pump relay The Powertrain Control Module (PCM) provides the ground path for the coil side of the relay on circuit K51. Circuit K51 connects to cavity 51 of the PCM connector.

When the PCM grounds the fuel pump relay and the contacts close, they connect circuits A14 and A61. Circuit A61 supplies power to the fuel pump motor.