Fuel Pump Electrical Circuit

When ignition is first turned to the On position, without engine running, the PCM turns the fuel pump relay On for 2 to 3 seconds. This builds up fuel pressure quickly. If engine is not started within two seconds, the PCM shuts the fuel pump Off and waits until ignition reference pulses are present. As soon as engine is cranked, the PCM turns the relay On which powers the fuel pump.