Seville V8-300 4.9L (1991)
Fuel Pump Relay: Description and Operation
Fuel Pressure Circuit
When the key is first turned "ON," without the engine running, the ECM/PCM will turn the fuel pump "ON" for two seconds. This builds up the fuel
pressure quickly. If the engine is not started within two seconds, The ECM/PCM will shut the fuel pump "OFF" and wait until reference pulses are
present. As soon as the engine is cranked, the ECM/PCM turns the relay "ON" and runs the fuel pump.
As a back up system to the fuel pump relay, the fuel pump can also be turned "ON" by the oil pressure switch. The oil pressure switch is a normally
open switch which closes when oil pressure reaches about 28 kPa (4 psi). If the fuel pump relay fails, the oil pressure switch will run the fuel pump.
An inoperative fuel pump relay can result in long cranking times, particularly if the engine is cold, and this should set Code E020.
An inoperative fuel pump would cause a no start condition. A fuel pump which does not provide enough pressure can result in poor performance.
