PUMP GP-FUEL TRANSFER 3334689 - Caterpillar

Illustration 1 g03684650
(1) Implement valve
(2) Pilot actuator solenoids
(3) Hydraulic oil supply
(4) Hydraulic oil outlet
(5) Implement lockout solenoid
(6) Hydraulic oil pressure switch
(7) Hydraulic oil supply pressure port The implement valve is mounted on top of the front frame, and directs oil from the implement pump to the implement cylinders. The implement valve is a post-compensated valve. The pilot actuator solenoids are mounted on the implement valve and control pilot oil to the ends of the directional valve spools. Oil from the implement pump flows through the supply hose into the inlet manifold. Return oil flows through the outlet hose to the tank. The implement lockout solenoid controls pilot oil to the actuator solenoids based on a signal from the Implement ECM. The implement pressure switch sends a signal to the Implement ECM indicating implement system pressure. Implement system supply pressure can be checked at the supply pressure tap.Hold Position
When all the control valves are in the HOLD position, the implement pump is at low-pressure standby. Pilot oil for the implement control valve is supplied from the brake/fan combination valve. A pressure reducing valve in the brake/fan combination valve regulates the pilot oil supplied to the implement control valve. The pilot oil flows to the pilot circuit in the implement valve and to the load sensing circuit. In the pilot circuit, pilot oil flows through a check valve to the pilot accumulator and to the pilot hydraulic lockout valve.The hydraulic lockout solenoid valve is in the CLOSED position until the hydraulic lockout switch in the cab is activated. The implement lockout solenoid valve is controlled by the implement lockout switch through the Implement ECM. When the implement lockout switch is in the OFF position, the Implement ECM de-energizes the implement lockout solenoid valve. Pilot oil is then blocked at the implement lockout solenoid valve. When the implement lockout switch is in the ON position, the implement ECM energizes the implement lockout solenoid valve. Pilot oil flows past the implement lockout solenoid valve to the pilot hydraulic actuator on each end of the control valve spools.Raise Position
When the lift control lever is moved into the RAISE position, the current proportional to the movement of the control lever is directed to the coil on the raise pilot solenoid valve. The solenoid valve sends a proportional amount of pilot oil to the raise end of the lift spool. The lift spool begins to shift down.As the lift spool shifts down, supply oil from the implement pump is directed to the lift pressure compensator valve. Then oil floes through an orifice and check valve to the implement pump compensator valve. The orifice stabilizes the load sensing signal pressure to the implement pump. That signal is sent to the spring chamber on each compensator valve, and to the margin relief valve. The load sensing signal moves the pump load sensing spool in the pump control valve to upstroke the pump.The load sensing pressure acts on the top of the margin relief valve. During the upstroke of