DeVille V8-4.6L VIN 9 (1995)
Fuel Pump Relay: Description and Operation
FUEL PUMP RELAY
The fuel pump relay allows the fuel pump to be energized by the PCM. When the ignition is first turned "ON," the PCM energizes the fuel pump
relay for two seconds. This allows the fuel pump to run for two seconds and build up fuel pressure for cranking. The PCM then waits for ignition
reference pulses from the Ignition Control Module (ICM). Once the PCM sees references pulses, the PCM energizes the relay to run the fuel
pump.
FUEL PUMP RELAY BACKUP SYSTEM
As a backup system to the PCM and fuel pump relay, the fuel pump can also be turned "ON" by the fuel pump switch and engine oil pressure
sensor. If the PCM or fuel pump relay is faulty and the engine is cranked, the fuel pump switch and engine oil pressure sensor contacts will close
once oil pressure is built up and the sensor will run the fuel pump.
FAULTY FUEL PUMP RELAY
A faulty fuel pump relay may cause long cranking times and should set a Diagnostic Trouble Code.
