Timing control for fuel injection pump

Claim 1

In a fuel injection pump for an internal combustion engine, pump plunger means providing sequential pumping strokes, means for changing the timing of the pumping strokes comprising a cylinder, an advance piston movable in said cylinder, means interconnecting said advance piston with said pump plunger means to advance and to retard the relative timing of the pumping strokes, a source of fluid having a pressure correlated with engine speed, a first hydraulic chamber at one end of said advance piston connected to said source of fluid to move the advance piston to advance the timing of the pumping strokes in response to increased engine speed, means for controlling the delivery of fluid from said source to said first hydraulic chamber, said means including means for preventing the delivery of fluid to said first hydraulic chamber until a predetermined speed is reached thereby to retard the timing of the pumping strokes during engine cranking, movable stop means engageable with said advance piston, a second hydraulic chamber for receiving fluid from said source to urge said movable stop toward said advance piston, and means providing continuous communication between said fluid source and said second hydraulic chamber whereby said movable stop limits the maximum retard position of said advance piston to a lesser amount as soon as the engine starts.