JLG G12-55A Service Manual - Manual (Page 121)

8-5 G10-55A, G12-55A
Hydraulic System
3. Tighten the jam nut and recheck the pressure at full
throttle. If the reading is within specification, shut the
machine off, install the safety cap and remove the
gauge from the test port.
4. If the proper pressure cannot be set, use the
accompanying hydraulic schematic and/or the
electrical schematic to help troubleshoot and correct
the problem.
8.4.2 Tilt Circuit Port Relief Adjustment
The following procedure is specific to the tilt circuit only
and should be performed and verified if the main and/or
load sense circuits pressures are in question.
1. Remove any attachment from the quick coupler
assembly. Refer to Section 3.9, “Quick Switch
Assembly.”
2. Raise the boom for access to the compensation
cylinder.
3. Slowly loosen and remove the retract (1) hose from
the compensation cylinder.
4. Install a tee fitting to the retract (1) port of the
compensation cylinder. Reconnect the previously
removed retract (1) hose to the tee fitting.
5. Slowly loosen and remove the extend (2) hose from
the compensation cylinder.
6. Install a tee fitting to the extend (2) port of the
compensation cylinder. Reconnect the previously
removed extend (2) hose to the tee fitting and cap
the open port.
7. Install a digital or a 5000 psi (345 bar) gauge to the
retract (1) port tee fitting on the compensation
cylinder.
8. Start the machine and warm the hydraulic system to
operating temperature.
9. Tilt the forks down to allow the tilt cylinder to fully
retract.
10. Monitor the gauge and slowly raise the boom. The
gauge should read 4100 psi (282 bar).
11. If pressure is correct, proceed to step 14.
12. If the pressure requires adjustment and if the
machine is equipped with a Rexroth main control
valve, adjust the relief on the (A) port and repeat
steps 9 and 10.
If the machine is equipped with a Husco main control
valve, the relief on the (A) port is non-adjustable and
must be replaced. Replace and repeat steps 9 and
10.
13. Verify pressure is correct.
14. Shut engine OFF.
15. Remove the digital or the 5000 psi (345 bar) gauge
from the retract (1) port tee fitting on the
compensation cylinder and cap the open port.
16. Remove the cap and install a digital or a 5000 psi
(345 bar) gauge to the extend (2) port tee fitting on
the compensation cylinder.
17. Start the machine and if needed, warm the hydraulic
system to operating temperature.
18. Tilt the forks up to allow the tilt cylinder to fully
extend.
19. Monitor the gauge and slowly lower the boom. The
gauge should read 4100 psi (282 bar).
20. If pressure is correct, proceed to step 23.
MY5520
2
1
MY4490
A
HUSCO
REXROTH
A
FRONT OF MACHINE