PUMP GP-GEAR 9J7900 - Caterpillar

Specifications
Table 1
Charging Pressure and Temperature Relationship for a Typical 1000 kPa (145 psi) Accumulator
Temperature Pressure
−7 °C (20 °F) 906 kPa (131 psi)
−1 °C (30 °F) 925 kPa (134 psi)
4 °C (40 °F) 943 kPa (137 psi)
10 °C (50 °F) 962 kPa (140 psi)
16 °C (60 °F) 981 kPa (142 psi)
21 °C (70 °F) 1000 kPa (145 psi)
27 °C (80 °F) 1019 kPa (148 psi)
32 °C (90 °F) 1038 kPa (151 psi)
38 °C (100 °F) 1057 kPa (153 psi)
43 °C (110 °F) 1075 kPa (156 psi)
49 °C (120 °F) 1094 kPa (159 psi) Machine Preparation for Troubleshooting
Move the machine to a smooth horizontal location. Move away from working machines and personnel. Lower the work tools to the ground.
Allow only one operator on the machine. Keep all personnel away from the machine or in the view of the operator.
Engage the parking brake.
Illustration 1 g03366569
Typical example
Place the steering frame lock in the LOCKED position.Reference: For more information about preparing the machine for troubleshooting, refer to the Service Manual module Testing and Adjusting, "Machine Preparation for Troubleshooting" for the machine that is being serviced.Pilot Oil Accumulator
The following procedure can be used in order to test the pilot oil accumulator. The pilot oil accumulator maintains pressure in the pilot hydraulic system. The accumulator allows you to lower the boom, and the work tools with a stopped engine.When you test or you charge the pilot oil accumulator, the pressure in the pilot hydraulic system must be released. The temperature of the nitrogen gas must also be taken into account. The pressure and volume of nitrogen gas varies with temperature.Operational Test for the Pilot Oil Accumulator
Table 2
Required Tools
Part Number Description Quantity
177-7860 Hose assembly 1
8T-0856 Pressure Gauge 1
Illustration 2 g06273559
The pressure tap is located on the non-engine end frame, left side, near the pilot oil filter, .
Install an 8T-0856 Pressure Gauge 4000 kPa (580 psi) on a 177-7860 Hose Assembly that has quick disconnect fittings. Install the other end of the hose to the pressure tap for the pilot pressure.
Start the engine and run the engine at HIGH idle. The pressure gauge will read 3515 345 kPa (510 50 psi).
Stop the engine. Turn the start switch to the ON position. Do not start the engine.
Move the implement control levers several times through the full range of travel. This process will relieve any pressure that may be present in the implement hydraulic system. Turn the key start switch to the OFF position.Note: For more information on releasing the hydraulic system pressure, refer to Testing and Adjusting, "System Pressure - Release".
Watch the pressure gauge. Move the control lever or the joystick in order to lower the boom. The pressure will steadily decrease.
When the pressure is approximately 1000 50 kPa (145 7.3 psi), the pressure will suddenly drop to zero. This drop occurs because no oil is left in the accumulator. The final pressure prior to the sudden drop to zero is the approximate