Fuel Pumps: Description
Three types of fuel supply pumps are used in current production models. Pumps are either externally mounted mechanically operated, externally mounted electrically operated, or internally mounted in the fuel tank and electrically operated. With the exception of the internally mounted pumps in the fuel tank, all pumps make use of a pulsating diaphragm and intake and discharge check valves. In-tank pumps make use of a motor driven vane type unit.
Regardless of the type pump installed, vehicle manufacturers state that if a fuel pump does not meet specifications as to fuel pressure, volume flow (capacity) or vacuum (suction), no attempt should be made to repair or overhaul the pump. The pump should always be replaced as an assembly.