it is possible in a simple manner , especially in distributor injection pumps , to attain quiet combustion in the idling range of a diesel engine , without modifying the basic construction of the fuel injection pump by shifting the injection pumping to the last portion of the stroke of the cam driving the pump piston of the fuel injection pump for idling , by means of an injection onset adjusting device , in combination with a determination of injection duration via the closing phase of an electrically controlled valve that relieves the pump work chamber .