A variable displacement pump and pump control system therefor to pump a fluid at selected pump output flow rates having a variable displacement pump and a fluid volume displacement selection controller to select a volume of fluid to be forced from the pump inlet to the pump outlet by the rotating member during a rotation thereof. A movable lead screw is coupled to the displacement selection controller so as to be capable of altering the position thereof, and a lead screw positioner is provided for selectively moving, or preventing the moving of, the movable lead screw by extending and retracting the lead screw through a threaded opening.