Your Fuel System

by: Kevin Schappell

The fuel system feed your engine the gasoline/diesel it needs to run. If any one part in the system break down your engine will not run. Let's look at the major parts of the fuel system.

Fuel tank: Basically a holding tank for your fuel. When you fill up at a gas station the gas travels down the filler tube and into the tank. In the tank there is a sending unit, which tells the gas gauge how much gas is in the tank.

Fuel pump: On newer cars the fuel pump is usually installed in the fuel tank. Older cars have the fuel pump attached to the engine or on the frame rail between the tank and the engine. If the pump is in the tank or on the frame rail then it is electric and is run by your cars battery. Fuel pumps mounted to the engine use the motion of the engine to pump the fuel

Fuel filter: Clean fuel is critical to engine life and performance. Fuel injectors have tiny openings, which clog easily so filtering the fuel is the only way to prevent this. Filters can be before or after the fuel pump, sometimes both.

Fuel injectors: Most domestic cars after 1986 and earlier foreign cars came from the factory with fuel injection. Instead of a carburetor to mix the fuel and air, a computer controls when the fuel injectors open to let fuel into the engine. This has resulted in lower emissions and better fuel economy. The fuel injector is basically a tiny electric valve, which opens and closes with an electric signal. In the picture below you can see the injectors towards the outer part of the intake. By injecting the fuel close to the cylinder head the fuel stays atomized ( in tiny particles ) so it will burn better when ignited by the spark plug.

Carburetors: A carburetor takes the fuel and mixes it with air without computer intervention. While simple in operation, they tend to need frequent tuning and rebuilding. This is why most newer cars have done away with carburetors in favor of fuel injection. 

Common Problems:

I would say the most common problem is a clogged fuel filter. Make sure you follow your manufacturers recommendations as to when you should change the fuel filter. This information should be in your owner’s manual. Symptoms include sputtering at high speeds or engine not starting at all. Always check the ignition system first, if that's ok then the next suspect is the fuel filter.

Next most common problem is the fuel pump failing. Most modern electric fuel pumps can be heard when you turn the key on. If you don't hear the pump running and your car will not start, it could be your fuel pump. The first thing a mechanic will check is the relay, which sends power to the pump. If this is operating correctly then the pump will have to be replaced.