HOSE AS 4I7816 - Caterpillar

Illustration 7 g03345112
Main control valve
(3) Pp port
Connect a 6895 kPa (1000 psi) pressure gauge to port "Pp" (3) on the main control valve. Use tooling group (A) and tooling group (F).
Start the engine and place the hydraulic lockout lever in the UNLOCKED position.
Shut off the engine by turning the start switch to the OFF position. When the engine has stopped, return the start switch to the ON position.
After the power loss, the accumulator will still have pilot system pressure. Use the stopwatch to observe the pilot pressure. The pilot pressure should stay above 1035 kPa (150 psi) for 1 minute. The pressure ensures that enough stored energy is available to lower the implements to the ground. Note: When, the pilot pressure in the accumulator is approximately 860 kPa (125 psi) the pressure will suddenly drop to zero. The drop in pilot pressure to zero occurs because no oil is left in the accumulator.
If the pilot pressure in the accumulator is below 1035 kPa (150 psi) or the pilot supply is exhausted in less than 1 minute, check valve (2) within the main control valve is not working properly.
Move the joysticks in order to release any pilot hydraulic pressure in the accumulator.
Turn off the engine.
Clean check valve (2). Check valve (2) is located above the pressure reducing valve on the main control valve. Repeat steps 3 through 5. If the test fails, replace check valve (2). Charging the Accumulator
Gas pressure is variable with temperature. Check the temperature of the air around the accumulator. In order to check the amount of charge in an accumulator, the accumulator must be at the same temperature as the surrounding air.Note: The temperature of the accumulator may change as the accumulator is being charged due to the expansion or compression of the nitrogen charge. It may be necessary to charge the accumulator in several steps in order to ensure a correct charge.
Table 2
Charge Pressures and Temperatures
Temperature Pressure
−25°C (−13°F) 1490 kPa (216 psi)
−20°C (−4°F) 1520 kPa (220 psi)
−15°C (5°F) 1550 kPa (225 psi)
−10°C (14°F) 1580 kPa (229 psi)
−5°C (23°F) 1610 kPa (233 psi)
0°C (32°F) 1640 kPa (238 psi)
5°C (41°F) 1670 kPa (242 psi)
10°C (50°F) 1700 kPa (247 psi)
15°C (59°F) 1730 kPa (251 psi)
20°C (68°F) 1760 kPa (255 psi)
25°C (77°F) 1790 kPa (260 psi)
30°C (86°F) 1820 kPa (264 psi)
35°C (95°F) 1850 kPa (268 psi)
40°C (104°F) 1880 kPa (273 psi)
45°C (113°F) 1910 kPa (277 psi)
50°C (122°F) 1940 kPa (281 psi)
Illustration 8 g03345110
Accumulator
(1) Charging port cap
Stop the engine. Release the pressure from the pilot hydraulic system. Refer to Testing and Adjusting, "Hydraulic System Pressure - Release". Note: If an accumulator has less than half of the required amount of precharge pressure, the accumulator should be charged. Oil in the accumulator will give an inaccurate precharge reading.
Make sure that valve (D6) is closed.
Remove charging port cap (1) from the accumulator.
Rotate the valve handle on chuck (D9) or (D10) counterclockwise until the valve handle reaches the