PUMP GP-GEAR 1788613 - Caterpillar

Hydraulic oil pressure can remain in the hydraulic system on this machine after the engine and pump have been stopped. Serious injury can result if this pressure is not released before any service is done on the hydraulic systems. In order to prevent possible injury, release the hydraulic system pressure before working on any fitting, hose, or hydraulic component.Lower all attachments to the ground before service is started. If the hydraulic system must be serviced, tested, or adjusted with the attachment in the raised position, the attachments and lift cylinders must be supported properly.Always move the machine to a location away from the travel of other machines. Be sure that other personnel are not near the machine when the engine is running and tests or adjustments are being made.
Introduction
The pressure reducing valve reduces the implement hydraulic pressure. The relief valve prevents excessive pressure buildup in the pilot system. If a high pressure situation occurs, the relief valve will open. Excess pressure is relieved through the valve.The pressure in the pilot system controls the response of the implements. Low pilot pressure produces poor response in the implement control levers. High pilot pressure produces extreme sensitivity in the implement control levers.The following test procedure will verify whether the pressure setting for the pilot pressure is within the specified limit. The following adjustment procedure will explain the procedure for adjusting the pilot pressure.Pilot pressure is controlled by the pressure reducing valve, which is located in the pilot manifold.Required Tools
Illustration 1 g01174942
Tooling (A)
Table 1
Required Tools    
Item    Part Number    Description    Qty    
A     6V-7830     Pressure Gauge     1    Test and Adjustment of the Pressure Reducing Valve
The pressure reducing valve is located behind an access door on the right fender of the operator station.
Illustration 2 g01199955
(1) Accumulator (2) Manifold and reducing valve (3) Pilot supply pressure (pressure after pressure reducing valve) (4) Relief valve (5) Pressure reducing valveNote: Low pilot pressure produces poor response at the pilot control levers. High pilot pressure produces extreme sensitivity at the pilot control levers.
Attach tooling (A) to pressure tap (3) for pilot pressure on the right fender.
Operate the engine at HIGH IDLE (2010) and exercise the implement hydraulics. The pilot pressure should be a maximum of 3275 175 kPa (475 25 psi).
If the pilot pressure is not correct, follow Steps 4 through 6 in order to adjust the pilot pressure.
Operate the engine and exercise the implement hydraulics.
Loosen the locknut on the adjustment screw of pressure reducing valve (5). Turn the adjustment screw until the pilot pressure is correct.Note: One turn adjusts the pilot pressure by 1380 kPa (200 psi).
Tighten the locknut on the adjustment screw to a torque of 12 N m (9 lb ft).Test of the Relief Valve
The pressure reducing valve is located behind an access door on the right fender of the operator station.
Illustration 3 g01199955
(1) Accumulator (2) Manifold and reducing valve (3) Pilot supply pressure (pressure after pressure reducing valve) (4) Relief valve (5) Pressure reducing valveThe relief