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What Are the Functions of the Fuel Pump?

by Andrea Stein

Vehicle engine systems require a constant supply of fuel, which is produced via a fuel tank. Fuel is drawn from this tank and propelled into the internal combustion engine via a fuel pump.

Fuel Pump Function

Fuel pumps pump gasoline from the vehicle’s fuel tank to the engine and also distribute fuel under low pressure to the carburetor or to the fuel injection system under higher pressure. Carburetor engines utilize low pressure pumps, which are located outside of the fuel tank. Fuel-injected engines typically utilize electric fuel pumps mounted in the fuel tank.

Mechanical Fuel Pump

Mechanical fuel pumps typically contain a flexible diaphragm. The pump chamber volume is decreased or increased by flexing the diaphragm. A lever on the pump is operated via the camshaft, which pulls down the diaphragm and enables fuel to be drawn into the pump. A diaphragm spring pulls the diaphragm up, applying force that enables fuel to be expelled from the pump.

Electric Fuel Pump

Electric fuel pumps generate positive electrical pressure in fuel lines, which drives fuel to the internal combustion engine. An ignition switch activates a relay that manages the higher current necessary to increase fuel pressure.

About the Author

This article was written by the It Still Runs team, copy edited and fact checked through a multi-point auditing system, in efforts to ensure our readers only receive the best information. To submit your questions or ideas, or to simply learn more about It Still Runs, contact us.

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  • Classic Car Engine Refurbished image by Janet Wall from