Most people know that their cars have fuel pumps, but they don’t really know how they operate. Some even pay attention to their fuel pumps only when they have already malfunctioned. It is important to know how a fuel pump works because it is a critical part of a car’s system.
It would be difficult to understand how a fuel pump operates without understanding first how an engine works. Cars run on an internal combustion engine that combusts fuel and air in a combustion chamber. The reaction creates hot and pressurized gases which expand. These gases then act on rotors, pistons and other parts of the engine, making the car move. An engine needs a fuel tank to store the fuel that it consumes. It also needs a carburetor or fuel injectors to be able to mix air and fuel. The fuel pump’s purpose is to bring the oil from the fuel tank to the carburetor.
There are two basic types of fuel pumps: mechanical and electric. Before fuel injectors became popular, most engines used mechanical fuel pumps. These pumps create negative pressure to extract fuel. Most mechanical pumps have diaphragms. A diaphragm is a flexible part of the fuel pump that increases and decreases the volume of a pump chamber. The engine’s camshaft drives a lever on the pump by pulling the diaphragm. The volume inside the pump increases and fuel is extracted into the pump from the fuel tank. A spring then brings the diaphragm to its former location and the fuel flows into the carburetor.
However, a common problem among mechanical fuel pumps is that fuel vaporizes in the supply line because of low pressure between the fuel tank and the pump. Instead of sucking liquid fuel, the pump sucks in vapors, which causes the engine to stall. This led to the development of electric fuel pumps which work more efficiently at higher fuel pressures. Electric pumps are usually located in the fuel tank. When the engine is turned on, the pump transfers fuel by creating a positive pressure in the fuel lines. The electric fuel pump delivers a steady flow of fuel into the engine, and unused fuel returns to the tank. It is safe to submerge the pump in the fuel tank because liquid fuel does not explode when ignited.
Fuel pumps fail to operate because of prolonged use or fuel contamination. Be sure to check your fuel pump for any problems because a defective pump can be dangerous while on the road.