Fuel Supply & Delivery System

The function of the vehicle's fuel system is to store and supply fuel to the engine. The engine intake system is where the fuel is mixed with air, atomized, and vaporized. Then it can be compressed in the engine cylinder and ignited to produce energy or power. Although fuel systems vary from engine to engine, all systems are the same in that they must supply fuel to the combustion chamber and control the amount of fuel supplied in relation to the amount of air.

The fuel is stored in the fuel tank and the fuel pump(s) draw fuel from the tank. It then travels through the fuel lines and is delivered through a fuel filter to the fuel injectors (carburetors and throttle body injection were used on older vehicles). As the fuel is delivered, the final conditions for providing complete combustion are atomization and the spray pattern of the fuel. Atomization is accomplished as a result of the injection pressure, due in part to the diameter of the holes in the injector. The spacing, angle and number of holes in the injector tip determine the spray pattern.

Depending on whether your vehicles fuel system is a return type or return-less type system, the fuel pressure is regulated differently. A return type system has a fuel pressure regulator that varies the fuel pressure based on the amount of vacuum from the intake system. This is so the amount of fuel pressure and flow of fuel as it reaches the injectors remains consistently the same. Where a return-less type system uses the ECM to control and regulate fuel delivery. There is a fuel pressure sensor mounted to the supply rail of the fuel injectors to allow the ECM to monitor fuel pressure. When the fuel pressure and flow starts to drop due to increase of engine speed or load the ECM compensates by increasing injector duration and/or operating speed of the fuel pump.