Fuel Pump Relay: Description and Operation

Fuse/Relay Box:

When ignition is switched "RUN" position (engine not running), ECM energizes fuel pump relay for two seconds, causing fuel pump to pressurize fuel system. If ECM does not receive ignition reference pulses (engine cranking or running) within two seconds, it will de-energize relay, stopping fuel pump.

After the engine starts, the ECM uses the signal from the EST module to determine if the engine is running. If the signal is interrupted, the ECM will not energize the fuel pump. This prevents the fuel from operating when the engine is not running.