JLG Skytrak 6036 Service Manual page 135

Section 9. Hydraulic System
Backward Position
When the auxiliary control lever is placed in the
backward position, the directional control valve
spool is positioned so that pump applied pressure
is directed through ports E to B, Fig. 9.8, to the
male quick connect coupler. Return pressure is
directed through ports A to D to the return filter
and reservoir. If the filter becomes clogged,
hydraulic oil will bypass the filter when the pres-
sure reaches 10 to 15 psi (0,7 to 1,03 bar).
b. Pressure Checks and Adjustments
1. Engage the park lock, place the travel select
lever in neutral, and stop the engine.
Warning !
Relieve hydraulic pressure before servicing any
hydraulic component. Escaping hydraulic fluid
under pressure can penetrate the skin causing
serious injury.
2. Operate the hydraulic controls after the engine
has stopped to relieve any trapped pressure.
Warning !
Wait for the hydraulic fluid to cool before servic-
ing any hydraulic component. Hot hydraulic fluid
can cause severe burns.
3. Remove the transmission cover from the
frame.
4. Install a tee and pressure gauge capable of
measuring 0-4000 psi (275,6 bar) in the 30
gpm section outlet of the tandem pump, Fig.
9.8.
Warning !
Before starting the engine be sure all hydraulic
connections are tight and all tools are removed
from the forklift.
Model 6036 S/N 9B0499 and Before
5. Start the engine and maintain engine speed at
1000 rpm.
6. Operate the auxiliary control function several
times to purge the system of air.
7. Place the auxiliary control lever in the forward
position and hold until the pressure readings
are taken.
8. Check the pressure gauge reading. It should
read 3,000 ± 50 psi (206,7 ± 3,4 bar).
If not, adjust the main relief valve, Fig. 9.2, by
turning the adjustment screw clockwise to
increase pressure or counterclockwise to
decrease pressure. Torque nuts on relief
valve to 10 ± 1.5 lb-ft (13,5 ± 2 N m) after
adjustment.
9. Place the auxiliary control lever in the back-
ward position and hold until the pressure
readings are taken.
10. Check the pressure gauge reading. It should
read 3,000 ± 50 psi (206,7 ± 3,4 bar). If not,
adjust the main relief valve, Fig. 9.2, by turning
the adjustment screw clockwise to increase
pressure or counterclockwise to decrease
pressure.
11. Stop the engine. Operate the hydraulic control
after the engine has stopped to relieve any
trapped pressure.
12. Remove the pressure gauge and tee from the
tandem pump and reconnect the hydraulic
line.
13. Start the engine. Operate the auxiliary control
fully several times to purge the system of air.
14. Install the transmission cover after adjustment.
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