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The investigations showed that the VIT positioning unit is moving in and out with each injection under the forces in the fuel injection pumps. This movement could have an amplitude of up to 1.5mm (peak-to-peak) and results in excessive wear on the positioner's feedback transmitter. In order to make the system robust agaiast these small but frequent movements, that have to be accepted and must be considered normal in the present arrangement, a backlash of 2mm (peak-to-peak) has been introduced between the piston rod and the feedback potentiometer. The resulting loss in positioning accuracy is within the acceptable tolerance for the VIT system. In addition the solenoid valves were changed to a rigid design based on experience with sticking valves of the previous design. However, those internal changes are not absolutely essential on all engine types and trouble-free operation of the original VIT has been experienced in many installations.