This fuel filter element removes particulate and water from the diesel supply before fuel reaches the injection pump. It is installed in the primary or secondary filter housing on the engine, where it protects the precision-ground plungers and nozzles from abrasive contamination. A restricted element causes a pressure drop that leads to hard starting, misfiring, or power loss under load. The filter uses a spin-on or cartridge-style construction with a gasket that must be replaced at each service interval. Tighten the housing to the specified torque to prevent air ingress into the fuel system.