DE2720279

An edge controlled fuel injection pump for internal combustion engines, whose axially and rotationally movable pump piston, guided within the pump cylinder, has an improved leakage oil return system, which avoids piston wear and increased oil leakage even under very high injection pressures and relatively short piston strokes. The pump piston has an annular leakage oil collecting groove next to, but separate from, the recess that serves to end the fuel delivery, and a plurality of narrow leakage oil return grooves, which are formed in the outer surface of the piston diametrically opposite the recess and are connected with the collecting groove. Of these leakage oil return grooves, at least one is always connected with a leakage oil bore in the pump cylinder to a chamber of low pressure in the pump during the useful stroke of the piston.