In older cars, the fuel is fed from the gas tank to the engine with only the force of gravity. However, in modern cars with fuel injection systems, a fuel pump is required to get fuel from the gas tank to the injection system much more efficiently. And efficiency means better gas mileage and increased performance for modern vehicles.
For most of the existence of the internal combustion engine, the carburetor has been the device that supplied fuel to the engine. But as the automobile evolved, the carburetor got more and more complicated trying to handle all of the operating requirements. In trying to keep up with emissions and fuel efficiency laws, the fuel system used in modern cars has changed a lot over the years. Fuel injection has been around since the 1950s. Now, all cars sold in the United States have fuel injection systems. At first, carburetors were replaced with throttle body fuel injection systems that incorporated electrically controlled fuel-injector valves into the throttle body. Gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection. These systems have a fuel injector for each cylinder. These systems provide more accurate fuel metering, better fuel mileage and quicker response.