Most cars on the road today use at least one electric fuel pump either inside the fuel tank or just outside of it. Older models use a manual fuel pump, especially if they make use of a carburetor instead of fuel injection. Automotive manufacturers decided to switch to the electronic version of the fuel pump in order to provide the high pressure fuel injectors need in order to operate efficiently. Let’s take a look at how fuel pumps work and why they are so important.
To begin with, the electronic fuel pump can be controlled by the engine control unit (ECU) so that the exact amount of fuel necessary will be delivered to the fuel injectors. The ECU monitors the throttle position as well as other factors during the operation of the vehicle, including the amount and composition of exhaust gases, to determine how much fuel is needed. Adjustments are constantly being made for the speed with which the electronic fuel pump operates.
The process of fuel pumping begins with the ECU sending a signal to the electronic fuel pump. This happens from the moment you begin to turn your key in the ignition of your car and in some cases may be audible, sounding like a slight “whirring” underneath the car. The fuel pump will continue to send the fuel at high pressure and at the rate required by the ECU at any moment during operation of the vehicle. Very much like a small water pump, a rotor with metal or plastic blades housed in the fuel pump, turn and pull fuel from the tank. The faster the rotor blades turn, the higher the fuel pressure will become.
The electronic fuel pump will become warm or even hot during operation, which is the reason most are located either inside the fuel tank or just outside the tank. This allows the pump to use the fuel in the tank to dissipate any heat built up by its operation. Because the fuel tank itself can become a vacuum of sorts, the chance that a warm electronic fuel pump could cause the fuel to ignite is nonexistent. However, when changing a fuel pump it is important to see that the pump is receiving no electrical service in order to minimize starting a fire. This can be accomplished by simply unplugging the fuel pump fuse found in the fuse panel or disconnecting the battery before work is commenced.