What Is a Fuel Lift Pump?

A fuel lift pump raises fuel to a higher level. It usually consists of a vertical cylinder and a piston. A flap or ball valves are in the piston or cylinder base. The lift pump moves the fuel by pressure.

Lift Pump Duties

• The fuel lift pump drives the fuel from a low pressure condition to a high pressure condition by raising fuel level in the fuel lines. Lift pumps will not push the fuel through the fuel line. That task is for the fuel pump.

Significance

• Fuel lift pumps are used on diesel engines. Fuel lift pumps can extend the life of the fuel system of an engine by ensuring it will have enough fuel to meet its demands. Other benefits of the fuel lift pump are increased fuel economy, stronger torque output and increased fuel flow rates. An engine can run without a fuel lift pump, providing the fuel lines are air tight and the fuel injectors are working.

Inoperative Lift Pumps

• Inoperative lift pumps can cause low fuel pressure which can lead to white smoke. Fuel lift pumps for Hummer 6.5 liter engines are powered by the oil pressure sending unit through a relay. An inoperative sending unit can prevent the lift pump from operating. Fuel filters should be changed at regular intervals to extend the life of the lift pump.