Fuel Pumps & Components

The fuel pump transfers fuel from the fuel tank to the carburetor or fuel injection assembly. Electric fuel pumps are used in fuel injection systems. They’re usually mounted inside the fuel tank and incorporated with the sending unit assembly that supplies a fuel level signal to the fuel gauge. The float bowl on a carburetor is supplied with fuel by an engine mounted mechanical fuel pump equipped with a lever driven by an eccentric on the camshaft.

The lever actuates a flexible diaphragm within the mechanical pump body. The up and down movement of the diaphragm creates a vacuum that draws fuel from the tank and also pushes fuel out of the pump into the carburetor feed line. Check valves within the pump ensure that fuel only moves in one direction. Fuel pressure generated by the pump will generally range from 4-7 psi. Low or no pressure and external leaks can be caused by a failed diaphragm.

A tank-mounted electric fuel pump is attached to a module or hanger assembly, which is affixed to an opening in the top of the fuel tank. Fuel lines and electrical connectors for the pump and sending unit are attached to the top of the module/hanger assembly. A module generally includes the pump, sending unit and float arm, a reservoir to ensure there is fuel available at the pump pickup, and a strainer to trap dirt and contaminants. A hanger assembly may or may not include the reservoir and/or sending unit and float. The pump can be a geroter, roller vane, or turbine design, with the latter being the most common on late model vehicles.

When the ignition key is turned, the PCM looks for a cranking signal from the crankshaft or camshaft sensor before energizing the fuel pump relay. The relay in turns applies voltage to the fuel pump. The pump motor runs, drawing fuel through the strainer and then pushing it through the fuel lines and fuel filter to the engine. Fuel pressure on a port injection system is typically 45-66 psi, while pressure on a throttle body injection system ranges from 9 to 18 psi. The float on the sender rises and falls with fuel level. The float arm is connected to a rheostat, which varies the current sent to the fuel gauge according to float position.

If the engine cranks but won’t start, listen for the pump. If the pump doesn’t run, check for voltage to the pump. If there is no voltage, or less than specified voltage, check the circuit including the fuel pump relay. If the pump runs, perform fuel pressure and volume tests. But no matter the source of the failure, we have the parts for the repair. We offer thoroughly tested, ready to install replacement fuel modules and hanger assemblies, as well as separate pumps, sender assemblies, and fuel pump strainers, so you can service your vehicle your way. We also have all the related installation essentials like mounting gaskets, seals, and pushrods.