Fuel Pump Relay: Description and Operation

FUEL PUMP ACTIVATION
When the ignition key is first turned to the "ON" position, the Engine Control Module (ECM) will energize the fuel pump for two seconds. This increases fuel pressure for cranking. If the engine is not running within two seconds, the ECM will shut off the pump and wait until the engine starts.

RELAY BACK-UP
The oil pressure switch is wired in parallel to the circuit to operate the fuel pump circuit in case of failure of the fuel pump relay. Failure of the fuel pump relay will probably cause increased cranking time especially during cold start up.