Lumina APV V6-3800 3.8L (1994)
Fuel Pump Relay: Description and Operation
Fuel Pump/Relay Circuit Diagram
When the ignition key is first turned to the "ON" position, the PCM will energize the fuel pump relay for two seconds. This increases fuel pressure for
cranking. If the engine is not running within two seconds, the PCM will shut off the relay and wait for a "START" signal. As soon as the engine is
cranked, the PCM will energize the relay and power the fuel pump. Once the engine is started, the oil pressure switch provides power to the fuel pump.
The pump will then continue operating as long as the ignition is "ON" and there is engine oil pressure. If oil pressure is low (enough to possibly cause
engine damage) the oil pressure switch interrupts power to the fuel pump.
NOTE: The fuel pump relay can be bypassed at the oil pressure switch to operate the fuel pump. Also, a faulty oil pressure switch can cause the pump to
run continuously whenever the ignition is "ON".
