A pressure sensor is mounted in the transition from the screw feeder to the piston pump to control the speed of the screw feeder augers. The pressure sensor is set to maintain a constant pressure in the transition regardless of pump speed or solids content of the material. As either fluctuate, the screw feeder speed responds to maintain this constant pressure. This pressure sensor maximizes pump cylinder fill efficiency and in turn maximizes the wear life of the wearing parts and minimizes power consumption.