Car Engine, Brief Fuel System Explanation

THE FUEL SYSTEM

The fuel system pumps fuel from the tank and mixes it with air so that the proper air/fuel mixture can flow into the cylinders (because to make the little explosion to work it needs oxygen) then it give out a little spark. Fuel is delivered in three common ways: carburetion, port fuel injection and direct fuel injection.

• In carburetion, a mechanism called a carburetor mixes fuel into air as the air flows into the engine.

• In a fuel-injected engine, the right amount of fuel is injected individually into each cylinder either right above the intake valve (port fuel injection) or directly into the cylinder (direct fuel injection).

I’ll be discussing the fuel injected engine.

As new engines were designed, ‘throttle body fuel injection’ was replaced by multi-port fuel injection (also known as port, multi-point or sequential fuel injection). These systems have a fuel injector to infuse fuel to each cylinder; it’s usually positioned so that they spray right at the intake valve. These systems provide more accurate fuel metering and quicker response.

When you step on the gas pedal, the throttle valve opens up, letting in air. The engine control unit (ECU, the computer that controls all of the electronic machinery on your engine) "sees" the valve open and increases the fuel rate in expectancy of more air entering the engine. It is important to increase the fuel rate as soon as the throttle valve opens: otherwise, when the gas pedal is first pressed, there may be a faltering as some air reaches the cylinders without enough fuel in it.

Sensors monitor the mass of air entering the engine, as well as the amount of oxygen in the exhaust.