Fuel Pump: Description and Operation

Fuel Supply Components:

Fuel Pump Operation:

The fuel pump, located under the car near the fuel tank (along with the fuel accumulator and filter), is a roller cell type high pressure positive displacement pump. It supplies fuel to the fuel distributor at approx. 95 psi (6.6 bar). The pump can provide more than the maximum required amount of fuel at slightly higher than normal system pressure. Fuel pressure is regulated to a lower pressure for normal operation. This ensures adequate fuel supply during high demand operating conditions (high speed-wide open throttle), while fuel circulates continuously through the system and back to the tank.

The pump operates only when the fuel pump relay is energized. The ECU energizes the fuel pump relay for approx. 5 seconds when the ignition is turned ON. After then, the relay is de-energized and the pump turns "OFF". The ECU then waits for a "cranking" signal before it will energize the relay again. Once the engine is started, the relay will stay energized as long as the ECU is getting an "engine running" signal from the ignition system. If the engine dies, the ECU will turn the relay OFF after 5 seconds so the pump doesn't run when the engine is not running.