If so, you may be wondering what type of service this is and why you need it. Here are some tips to help you understand why you would need a fuel system service (and why you might not): First, you should understand a bit about how your car's engine operates. Fuel systems have changed drastically over the years. Old cars used to have a carburetor that fed fuel to the engine. However, carburetors were far from efficient and auto manufacturers eventually developed a fuel injection system that electrically controls fuel injection.