In mechanical fuel pump systems, a moving diaphragm creates a vacuum that sucks fuel to the engine. Diaphragm pumps are located on the engine and are operated by eccentric cams on crankshafts. Attached to the eccentric is a rocker arm that moves, flexing the diaphragm, which pumps fuel into the engine. Unlike mechanical fuel pumps that need to be located near the engine, electric fuel pumps can be placed anywhere in the car, but work the best when they are installed near fuel tanks. Newer fuel pumps are often located within the fuel tanks themselves.
Mechanical fuel pumps are manufactured to operate at pressures between 4 and 6 lbs. per square inch (psi). Electric fuel pumps, on the other hand, are capable of operating at pressures between 30 and 40 psi.
There are two types of electric fuel pumps available to fuel pump consumers: High pressure electric fuel pumps and low pressure electric fuel pumps. When a fuel pump needs to be replaced, you should make sure that the correct pump is being installed as low pressure and high pressure electric fuel pumps look the same.
Probably the biggest difference between mechanical fuel pumps and electric fuel pumps is the pressure output difference. Automobiles that feature fuel injection systems employ electric fuel pumps. Automobiles that use carburetors typically utilize mechanical fuel pump technology.
Fuel pumps that have leaks in them are dangerous, as leaking fuel can ignite. Regular maintenance should be scheduled to assure that a car's fuel pump is in proper working order. Care should be taken when handling fuels such as gasoline because it is flammable and harmful to touch or inhale.