LINES GP-PILOT 2608219 - Caterpillar

that is applied across the compensation land of the pilot valve plunger. This pressure differential is accomplished by the buffer system.Decreased Engine Load
With the pilot valve "centered," no oil flows to or from the power piston. If there is a decrease in load (causing an increase in engine speed), the solenoid coils will get a voltage signal to lift the pilot valve plunger. The oil under the power piston will now be released to go to sump. Pump pressure oil on the right side of the buffer piston will now force the buffer piston to the left. This displacement of oil in the power cylinder oil pressure circuit will move the power piston down and cause rotation of the terminal shaft in the decrease fuel direction.The movement of the buffer piston to the left also decreases the compression of the buffer spring on the right side, and increases the compression of the buffer spring on the left side. The increase of the left buffer spring force (caused by resistance to this movement) results in a small decrease in oil pressure on the left side of the buffer piston and on the bottom surface of the pilot valve plunger compensation land. This pressure difference on the two sides of the compensation land makes a force (greater at the top) to push the pilot valve plunger back down to the "centered" position.When the terminal shaft has turned far enough to satisfy the new fuel requirement, the force of the pressure difference on the compensation land will have again "centered" the pilot valve plunger (even though the engine speed is not yet completely back to normal). The movement of the power piston, and the terminal shaft, is now stopped.The continued decrease of engine speed to its steady-state setting results in a continued increase in downward force to the pilot valve plunger as the 2301 Control signal (to the solenoid coils) increases to its on-speed value. At the same