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 A fuel tank (also called a petrol tank or gas tank) is a safe container for Flammability, flammable fluids, often gasoline or diesel fuel. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine sys ...

to the device where it is mixed with the intake air (such as the

carburetor A carburetor (also spelled carburettor or carburetter) is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Ventu ...

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 Manifold injection is a mixture formation system for internal combustion engines with external mixture formation. It is commonly used in engines with spark ignition that use petrol as fuel, such as the Otto cycle, Otto engine, and the Wankel engine ...

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

(e.g. in older cars, lawnmowers and power tools), a mechanical fuel pump is typically used in order to transfer fuel from the

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 pump A plunger pump is a type of positive displacement pump where the high-pressure seal is stationary and a smooth cylindrical plunger slides through the seal. This makes them different from piston pumps and allows them to be used at higher pressure ...

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.Mollenhauer, K., & Tschöke, H. (2010). ''Handbook of Diesel Engines''. Berlin: Springer- Verlag.

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. The pump is similar to that of a radial piston-type pump, but instead of a piston it has a machined plunger that has no seals. When the plunger is at top dead center, the injection to the cylinder is finished and it is returned on its downward stroke by a compression spring. Due to the fixed height of a cam lobe, the amount of fuel being pumped to the injector is controlled by a rack and pinion device that rotates the plunger, thus allowing variable amounts of fuel to the area above the plunger. The fuel is then forced through a

check valve A check valve, non-return valve, reflux valve, retention valve, foot valve, or one-way valve is a valve that normally allows fluid (liquid or gas) to flow through it in only one direction. Check valves are two-port valves, meaning they have ...

and into the fuel injector nozzle.

Plunger-type pumps

Plunger-type pumps are a type of positive-displacement pump used by diesel engines. These pumps contain a chamber whose volume is increased and/or decreased by a moving plunger, along with check valves at the inlet and discharge ports. It is similar to that of a piston pump, but the high-pressure seal is stationary while the smooth cylindrical plunger slides through the seal. Plunger-type pumps are often mounted on the side of the injection pump and driven by the

camshaft A camshaft is a shaft that contains a row of pointed cams in order to convert rotational motion to reciprocating motion. Camshafts are used in piston engines (to operate the intake and exhaust valves), mechanically controlled ignition syst ...

.Judge, A. (1965). ''Modern Smaller Diesel Engines'' (Vol. 7). Cambridge, Massachusetts: Robert Bentley Inc. These pumps usually run at a fuel pressure of .

Electric pumps

In fuel-injected petrol engines, an electric fuel pump is typically located inside the fuel tank. For older port injection and throttle-body injection systems, this "in-tank" fuel pump transports the fuel from the fuel tank to the engine, as well as pressurising the fuel to typically . While for direct-injection systems, the in-tank fuel pump transports the fuel to the engine, where a separate fuel pump pressurises the fuel (to a much higher pressure). Since the electric pump does not require mechanical power from the engine, it is feasible to locate the pump anywhere between the engine and the fuel tank. The reasons that the fuel pump is typically located in the fuel tank are: * By submerging the pump in fuel at the bottom of the tank, the pump is cooled by the surrounding fuel * Liquid fuel by itself (i.e. without oxygen present) isn't flammable, therefore surrounding the fuel pump by fuel reduces the risk of fire In-tank fuel pumps are often part of an assembly consisting of the fuel pump, fuel strainer and fuel level sensor (the latter used for the fuel gauge).

Turbopumps

Rocket engines use a turbopump to supply the fuel and oxidizer into the combustion chamber.

References

{{Automotive engine , expanded Pumps Engine fuel system technology Engine components