The purpose of any diesel fuel filter is to remove foreign particles as well as water. The use of a suitable filtration system on diesel engines is a must to avoid damage to closely fitted injection pump and injector components. Filter’s ability varies between the type and manufacturer. On diesel engines primary and secondary filters are used. The primary filter is capable of removing dirt particles down to 30 microns and the secondary filter between 10 to 12 microns. Secondary filters are available between 3 and 5 microns, which are used in severe service operations. The primary filter is usually located between the tank and the supply pump, the FWS is one type of the primary filters. The secondary filter between the supply pump and the injection pump.
Diesel fuel filter is referred to as full-flow filter, because all the fuel must pass through it before reaching the injection pump. Some filters use internal replaceable element inside a bowl or shell. These are commonly referred to as a shell and element design. Most fuel filters used today are of the spin-on type, which allow for faster change out since the complete filter is a throwaway.
Besides, if the filter is installed on the pressure side of the boost pump it must have sufficient strength to handle pump pressure without bursting or leaking. The filter must be located well away from sources of heat, preferably outside of the engine compartment.
