Fuel Systems: Gasoline Fuel Systems: Carbureted system components
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Topic IntroductionHelp

Electric fuel pumps

Summary
An electric fuel pump operates with the ignition switched on. It can be controlled so that it operates only if the engine is running.

Carburetor systems can also use electric fuel pumps.

Most of these pumps are located outside the tank, though some are inside the tank.

One widely-used pump is the diaphragm type. It has an electrical section, and a mechanical section.

When the ignition is switched on, current magnetizes the solenoid. The magnetic field energizes the armature, which pulls down the diaphragm. This creates an area of low-pressure that draws fuel into the pump.

Pulling down the diaphragm breaks the circuit and stops the current. The solenoid is no longer an electromagnet. The armature is released, and the diaphragm spring forces up the diaphragm, which forces fuel out of the pump and on its way to the carburetor. This action continues, delivering fuel each time.

When the engine needs less fuel, pressure builds up in the fuel lines to the carburetor, and reduces how much fuel is delivered.

Some carburetor-equipped vehicles with electric pumps have a safety switch that prevents the pump continuing to run if the engine stops.