The flow output of the Rexroth variable plunger pump is fixed under normal conditions. Once the flow fluctuates, it means that something may happen to the plunger pump. There are many influencing factors of output flow fluctuation. Foreign matter entering the plunger pump, or scratches or wear marks in the pump will affect the normal flow output. Due to insufficient amplifier energy, damaged parts, and poor performance of the damper of the control piston containing springs, the motion of the control piston will be unstable.