This fuel filter removes particulate and water from the fuel supply before it reaches the injection pump. It is installed in the fuel line between the tank and the high-pressure pump, where it protects the injector nozzles and pump internals from abrasive contamination. A restricted filter reduces fuel flow, causing power loss and hard starting under load. The filter housing seals against the mounting head using the integrated gasket; on replacement, ensure the old gasket is removed and the new one is seated cleanly. Tighten the housing by hand until the gasket contacts the head, then give an additional partial turn as specified.