Fuel Pump Electrical Circuit

When the ignition is first turned to the On position, without the engine running, the PCM turns the fuel pump relay On for two to three seconds. This builds up the fuel pressure quickly. If the 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 the engine is cranked, the PCM turns the relay On which powers the fuel pump.