How Fuel Pumps Work

Step by step explanation on how an automotive fuel pump works. This article pertains to most fuel injected vehicles.

Step 1 - A fuel pump starts by being submerged inside of a fuel tank which is common among all fuel injected vehicles. The sump holds fuel near the pump inlet.

Step 2 - A connector is located near the top of the fuel tank, which is used to supply power and ground for the fuel pump and sensing wires of the fuel level sender.

Step 3 - A corrugated fuel tube is used to connect the pump to the top of the tank through the cap plate.

Step 4 - Sometimes held in by clips the fuel pump can by mounted to the top plate and be serviced as a unit.

Step 5 - The pump body is where an electric motor is mounted to a small vein pump which picks up gas and then pressurizes the fuel system.

Step 6 - The fuel level sender is attached to the fuel pump housing. This float rides on the fuel level while the sensing resistor provides feedback data for the computer.

Step 7 - A pre-filter is used to keep large debris from the pump inlet which would hinder pump performance.

Step 8 - Once the fuel has been pressurized, the fuel filter cleanses it before traveling into the fuel injection system.

Step 9 - A fuel pressure regulator is used the control pressure maintained in the system.

Helpful Information

A fuel injection system is more efficient than its predecessor, the carburetor, and can better operate in extreme conditions. Electric fuel pumps can experience wear and tear on the armature, brushes or bearings, which causes a gradual loss of pressure. An inlet filter sock is designed to block tank sediments. Running the fuel pump out of gas can cause premature failure.

Best Practices

• Inspect the fuel tank for sediment when replacing the pump.
• To extend pump life replace the fuel filter at regular intervals.
• Service the throttle body and idle control valve when replacing the fuel filter.

Our certified car repair technicians are ready to answer your car questions.

Related Car Repair Information

• How to Replace a Fuel Pump
• How to Test a Fuel Pump
• How to Replace a Fuel Filter