Fuel Tank and Fuel Supply Pump

The fuel tank is a reservoir that holds the fuel supply and helps maintain its temperature at a level below its flash point. The fuel tank also serves as an important means of dissipating heat from the fuel that is returned from the engine [Bosch 1971]. The fuel tank should be corrosion-resistant and leakproof to pressures of at least 30 kPa. It must also use some means to prevent excessive pressure accumulation such as a vent or a safety valve.

The fuel supply pump, often referred to as the lift pump, is responsible for drawing fuel from the tank and delivering it to the high pressure pump. Modern day fuel pumps can be electrically or mechanically driven by the engine. Using an electrically driven fuel pump allows the pump to be placed anywhere in the fuel system including inside the fuel tank. Pumps driven by the engine are attached to the engine. Some fuel pumps may be incorporated into units that serve other functions. For example, so called tandem pumps are units that incorporate a fuel pump and a vacuum pump for the brake booster. Some fuel systems, such as those based on a distributor type pump, incorporate a mechanically driven supply pump and the high pressure pump in one unit.

Fuel pumps are commonly sized to deliver more fuel than is consumed by the engine at any particular operating system. This extra fuel flow can serve a number of important functions including providing extra fuel to help to cool injectors, pumps and other engine components and maintaining a more constant temperature of the fuel in the entire fuel system. Also, the excess fuel that is heated by its contact with hot engine components can be returned to the tank or fuel filter to improve the vehicle’s low temperature operability.