Fuel filters

FUEL FILTERS

General Information

A fuel filter is a filter in the fuel line that screens out dirt and rust particles from the fuel. They are found in most internal combustion engines.

What does it do?

Fuel filters serve a vital function in today's modern, low-tolerance engine fuel systems. Unfiltered fuel may contain several kinds of contamination including paint chips and dirt, and rust, caused by moisture in a steel tank. Due to the abrasive action of the particles, on the high-precision components used in modern injection systems, if these substances are not removed from the fuel before it enters the system they will cause rapid wear and failure of the fuel pump and injectors. Fuel filters also improve performance, as the fewer contaminants present in the fuel the more efficiently it can be burnt.

To maximise efficiency fuel filters need to be maintained at regular intervals. This is usually carried out by disconnecting the filter from the fuel line and replacing it with a new one, although some specially designed filters can now be cleaned and reused many times.

If a filter is not replaced regularly it may become clogged with contaminants restricting the necessary fuel flow to the engine and causing an appreciable drop in engine performance.

How Does It Work?

Carburetor systems
In carburetor systems the fuel pump aspirates the fuel from the fuel tank and pumps it in the carburetor. An 'in-line' filter is situated in the line between the tank and the carburetor to prevent the contaminants in the fuel blocking the nozzles in the carburetor and causing engine problems.

The in-line filter is a small filter element in nylon housing with a filtration quality of 20 microns. The nylon housing has connecting pipes to the fuel line and is transparent so that serious contamination can be observed. The in-line filter must be replaced in accordance with the instructions of the manufacturer.
 
Fuel Injection systems
The components of injection systems are much more sensitive to contamination than carburetor systems. Therefore, these systems always have a fuel filter, either an in-tank or an in-line filter. The fuel pump, usually mounted in the fuel tank, aspirates the fuel in the tank and pumps it via the filter element to the injectors.

The filter element is finer than the carburetor system at 5 to 7 microns and is also used to absorb any water in the fuel. The element is mounted in a metal housing usually on the underside of the car; therefore the housing must resist salt spray.