Fuel Pump Relay: Description and Operation

PURPOSE
The relay supplies battery voltage to fuel pump and oxygen sensor heater element when energized by Jeep/Truck Engine Controller (JTEC).

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

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

The JTEC 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 Jeep/Truck Engine Controller (JTEC) provides the ground path for the coil side of the relay on circuit K51. Circuit K51 connects to cavity 51 of the JTEC connector.

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

CIRCUIT OPERATION
Circuit A61 from fuse 8 in the Power Distribution Center (PDC) supplies battery voltage to the contact side of the fuel pump relay Circuit A21 from the ignition switch powers circuit F18 through fuse 19 in the fuse block. Circuit F18 supplies battery voltage to the coil side of the Automatic Shut Down (ASD) and fuel pump relays. The Powertrain Control Module (PCM) provides the ground path for the coil side of the fuel pump relay on circuit K31. Circuit K31 connects to cavity C19 of the PCM connector.

When the PCM grounds the fuel pump relay and the contacts CLOSE, circuits A61 and A141 are connected. Circuit A141 supplies voltage to the fuel pump motor (part of the in-tank fuel pump module).