upon further inspection i have 3-4 degrees of chain stretch and i cracked all injector lines and no change.i pulled the rack bolt and the rack it is still in the pump.i also took a 4 ft long wood rod and held to all the injectors which turned up a slight knock noise on #4 then i did the same on the pump delivery valves which turned up a even louder knock from the #4 delivery valve.i dont know what to make of it can someone enlighten me?do i have bad delivery valve?