Circuit Opening Relay

When the key is first turned on (key in "Run" position with engine off), the ECM will turn the fuel pump relay on for two seconds. This builds up the fuel pressure for cranking. If the engine is not started within two seconds, the ECM will shut the fuel pump off and wait until distributor reference pulses are present. As soon as the engine is cranked, the ECM will turn the relay on and run the fuel pump.