Abstract: In a fuel injection pump having a cam and pump plungers movable relative to the cam to translate the contour of the cam into a sequence of pumping strokes. An advance piston connected to the cam to adjust the timing of the pumping strokes is controlled by a hydraulic pressure which increases with engine speed. The advance piston mounts a servo valve having a preloaded biasing spring to prevent the delivery of hydraulic pressure to act on said advance piston until a predetermined speed is reached. A movable stop controls the maximum retard position of the advance piston and responds to the hydraulic pressure which is continuously applied to the movable stop and acts to advance the timing a fixed amount as soon as the engine fires. A load sensing piston actuated by a load related source of fluid pressure is operatively connected to the other end of the advance piston to urge the advance piston in a direction to retard the timing of the pumping stroke in response to increased engine load.

Abstract: A fuel injection pump having a cam and pump plungers movable relative to the cam to translate the contour of the cam into a sequence of pumping strokes is disclosed. An advance piston connected to the cam to adjust the timing of the pumping strokes is controlled by a hydraulic pressure which increases with engine speed. The advance piston mounts two control pistons one of which controls the delivery of hydraulic pressure to the advance piston after a predetermined engine speed is reached and the other bypasses the first to control the delivery of the hydraulic pressure during starting and until a lower engine speed is reached.