A fuel pump is a component used in many liquid-fuelled engines (such as petrol/gasoline or diesel engines) to transfer the fuel from the fuel tank to the device where it is mixed with the intake air (such as the carburetor or fuel injector).
Carbureted engines often use low-pressure mechanical pumps that are mounted on the engine. Fuel injected engines use either electric fuel pumps mounted inside the fuel tank (for lower pressure manifold injection systems) or high-pressure mechanical pumps mounted on the engine (for high-pressure direct injection systems).
Some engines do not use any fuel pump at all. A low-pressure fuel supply used by a carbureted engine can be achieved through a gravity feed system, i.e. by simply mounting the tank higher than the carburetor. This method is commonly used in carbureted motorcycles, where the tank is usually directly above the engine.
Low-pressure mechanical pumps
On engines that use a carburetor (e.g. in older cars, lawnmowers and power tools), a mechanical fuel pump is typically used in order to transfer fuel from the fuel tank into the carburetor. These fuel pumps operate at a relatively low fuel pressure of .
The two most widely used types of mechanical pumps are diaphragm pumps and plunger pumps.
High-pressure mechanical pumps
Pumps for modern direct-injection engines operate at a much higher pressure, up to and have configurations such as common rail radial piston, common rail two piston radial, inline, port and helix, and metering unit. Injection pumps are fuel lubricated which prevents oil from contaminating the fuel.
Port and Helix pumps
Port and Helix pumps are most commonly used in marine diesel engines because of their simplicity, reliability, and its ability to be scaled up in proportion to the engine size. These pumps usually run at a fuel pressure of .