Automotive Fuel Systems

The fuel system of a vehicle stores the fuel and delivers it to the engine in the correct quantity and at the correct time so that combustion produces useful power. Its core components are the fuel tank, a pump that moves fuel toward the engine, filters that remove contaminants, and a metering device that controls how much fuel reaches the cylinders.

In most modern petrol engines, electronic fuel injection sprays measured fuel into the intake or directly into the cylinder, where it mixes with air; sensors and an engine control unit adjust the amount continuously to suit load, speed and temperature. Older engines used a carburettor, which blended air and fuel by drawing fuel through narrow passages as air flowed past. A diesel engine works differently: it injects fuel at high pressure into air that has already been compressed and heated enough to ignite the fuel without a spark, which makes diesel fuel systems operate at much higher pressures.

Fuel systems can be designed or adapted for a variety of fuels besides ordinary petrol and diesel. Hydrogen, natural gas and propane are gaseous fuels stored under pressure and require sealed, pressurised delivery, while methanol and other alcohols are liquids that may need materials resistant to their corrosive effects. The choice of fuel affects tank design, the materials used and the way fuel is metered. Mechanical linkages such as cam-and-follower arrangements have historically driven fuel pumps and injection timing in some engines. Whatever the fuel, the system's task is the same: supply a clean, correctly proportioned charge to the engine on demand.

Frequently asked questions

How does a diesel fuel system differ from a petrol one?

A diesel system injects fuel at high pressure into already-compressed hot air, which ignites it without a spark, so it operates at far higher pressures than a petrol injection system.

What replaced the carburettor in modern cars?

Electronic fuel injection replaced the carburettor; it sprays a precisely metered amount of fuel controlled by sensors and an engine control unit, improving efficiency and emissions.

Can a fuel system handle gaseous fuels like hydrogen or propane?

Yes, but gaseous fuels are stored under pressure and need sealed, pressurised tanks and delivery components, which differ from the system used for liquid petrol or diesel.