A pump system for pumping a fluid includes a motor housing, a motor, a rod, a positive displacement pump, a position sensor, and a controller. The motor is located within the motor housing. The rod is connected to and driven by the motor and the positive displacement pump for moving a fluid is driven by the rod. The position sensor produces a rod position signal that is a function of a position of the rod, and the controller produces a drive signal for driving the motor as a function of the rod position signal.