Fuel Pump: Description

All fuel pumps will be either the mechanical or electrically operated design. Most carbureted vehicles use an engine-mounted mechanical pump. On some General Motors vehicles, an electric supply pump is used in conjunction with the mechanical pump to assist in avoiding vapor lock in high temperatures. Also used is an extra connection for fuel and vapor return. This feature will assist in hot starting by preventing vapor lock.

Gasoline engine vehicles with fuel injection use an electric fuel pump to supply higher pressure demands required with these systems. Electric fuel pumps are normally located in or near the fuel tank. Some models use a low pressure and a high pressure electric pump. Generally, one pump will be located in the fuel tank, and the other externally. This provides adequate fuel delivery during high demand maneuvers and on steep inclines when the fuel tank is near empty.

When trouble shooting fuel pumps, remember that electric fuel pumps do not operate unless a reference signal is received from the distributor. Verify that the unit has enough pressure, volume, and vacuum (suction). When found defective, it is recommended that the fuel pump be replaced as an assembly.