PUMP GP-PISTON 3849437 - Caterpillar

Illustration 1 g00521427
Dual Horsepower Mechanism ( Type VI) (1) O-ring (2) Plug (access hole) (3) Oil gallery (4) Seal (5) Spring (6) Valve cavity (7) Collar (8) Piston assembly (9) Nut (10) SetscrewThis is the first type of two types of dual horsepower mechanisms. The dual horsepower mechanism is used to limit horsepower under certain operating conditions. When high horsepower is activated, the movement of the internal governor linkage is limited when the torque cam is contacted by the torque lever. This is the normal method of limiting fuel output. When low horsepower is activated the movement of the FRC lever is restricted by the dual horsepower mechanism. This determines maximum fuel output and engine power. When low horsepower is activated, the torque cam is not contacted and the governor is held constant.To activate low horsepower, the solenoid must be de-energized. The solenoid is located in valve cavity (6). When the solenoid is de-energized, oil is allowed to flow into oil gallery (3). This oil pressure acts upon piston assembly (8) and spring (5) by pushing the piston assembly toward the internal governor linkage. The oil pressure will continue pushing the piston assembly until the full stroke of the piston is reached. This limits the internal governor linkage in the fuel on direction so there is less fuel output and less horsepower. The rack position for low horsepower is set with setscrew (10) which is located in the dual horsepower mechanism.To activate high horsepower, the solenoid must be energized. When the solenoid is energized, oil is restricted from entering oil gallery (3). Instead, oil that is already in the oil gallery flows back through the solenoid into the governor. This reduces the pressure against piston assembly (8). Spring (5) moves the piston assembly away from the internal governor linkage. This allows the internal linkage to move further in the fuel on direction which provides more horsepower. The rack position for high horsepower is set with the torque cam screw that is located on the torque cam lever of the governor.The position of the internal governor linkage for low horsepower is set with setscrew (10) at the end of the assembly. This setscrew contacts the internal governor linkage when low horsepower is activated. The position of the internal governor linkage for high horsepower is not set by the dual horsepower mechanism. That position is set by the load stop lever in the governor.