Abstract: A pressure protection system including a valve for isolating an auxiliary fluid circuit from a main fluid circuit when a leak occurs in the auxiliary fluid circuit. A valve is connected between a governor controlled compressor and the main fluid circuit and a pressure protection valve is connected between the compressor and an auxiliary fluid circuit. If a leak develops in the auxiliary fluid circuit, the pressure protection valve closes which permits most of the output from the compressor to be used to recharge the main fluid circuit. The pressure protection valve includes a supply passage and a delivery passage disposed substantially perpendicular to the supply passage. A plunger member is movable within the delivery passage for closing the supply passage when there is insufficient fluid pressure in the auxiliary fluid circuit.