Grand Prix V6-204 3.4L DOHC (1992)
Fuel Pump Relay: Description and Operation
Fuel Pump Relay
When the ignition switch is turned to the ON position (before engaging the starter), the ECM turns the fuel pump relay ON for two seconds, causing the
fuel pump to pressurize the fuel system. If the ECM does not receive ignition reference pulses (engine cranking or running) within two seconds, it shuts
OFF the fuel pump relay, causing the fuel pump to stop.
As a back-up system to the fuel pump relay, the fuel pump also can be turned ON by the oil pressure sensor/switch. The oil pressure sensor/switch has
two internal circuits. One circuit operates the oil pressure indicator or gauge in the instrument cluster, and the other circuit is a normally open switch
which closes when oil pressure reaches about 28 kPa (4 psi). If the fuel pump relay fails, a Code 54 will be set in the ECM, and the oil pressure switch
runs the fuel pump.
An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold. The oil pressure switch turns ON the fuel pump as
soon as the oil pressure reaches about 28 kPa (4 psi).
