This general description of your fuel system should help you understand how it supplies fuel to your motor and allows you to operate your vehicle. The description applies to a fuel-injector type system.

Note: this is a general description. Consult a repair manual written specifically for your car, truck, van or SUV for exact descriptions. Your vehicle may have some, all or none of these mechanisms.

An electric (mechanical) fuel pump supplies fuel under pressure to the fuel rail. The fuel rail distributes fuel evenly to all the fuel injectors. A fuel filter located between the fuel pump and the fuel rail protects the system components. From the fuel rail, the fuel injector injects fuel into the intake ports, which are located near the intake valves.

The powertrain control module (PCM), commonly called the onboard computer, has "drivers" in it that control the amount of fuel that the injectors supply. The PCM employs signals from crankshaft and camshaft sensors to determine when to trigger each injector in firing-order sequence for each cylinder. Controlling the injectors this way makes for better fuel economy, fewer emissions, and more power.

There is always more fuel in the fuel rail than the injectors need in order to prevent fuel starvation. Excess fuel automatically returns to the fuel tank, if necessary.