A high pressure piston fuel pump having a discharge check valve between the pumping chamber and a pressurized fuel reservoir and a pressure relief valve between the fuel reservoir and a passageway in the housing, wherein the discharge check valve and the pressure relief valve are contained within a single fitting assembly affixed at the pump housing. A first end flow passage is in fluid communication with the pumping chamber and provides an inlet to the discharge check valve and an outlet from the pressure relief valve. A second end flow passage is in fluid communication with the fuel reservoir and provides an outlet for the discharge check valve and an inlet for the pressure relief valve. Advantages include the ability to pre-test the outlet check and pressure relief prior to assembly into the pump housing, and improved flexibility of the outlet fitting location.