Abstract: A protective cap for a diesel fuel filter which is placed on the working end of the filter by the filter manufacturer prior to sale to prevent dirt and other contaminants from getting into filter, particulary on the downstream side of the filtering material. The diesel fuel filter comprises a canister having an open working end partially covered by a circular apertured wall in which there is a large central aperture opening to a cavity in the canister on the downstream side of the filtering material. The filtering material forms an annular ring surrounding the central cavity. A series of smaller apertures extend around the outer periphery of the apertured circular wall which receive diesel fuel during operation on the upstream side of the filtering material. The fuel then passes through the filtering material into the central cavity where it then flows to the diesel pump when the filter is mounted in place on the diesel engine.