JLG Skytrak 6036 Service Manual page 117

Section 9. Hydraulic System
GRILLE TILT
FRAME TILT
"UP" PORT
"RIGHT" PORT
RELIEF VALVE
RELIEF
VALVE
GRILLE TILT
"DOWN" PORT
FRAME TILT
RELIEF VALVE
"LEFT" PORT
RELIEF VALVE
Fig. 9.2 Main Control Valve Relief Valves
Boom Hoist Port Relief Valve
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.
Model 6036 S/N 9B0499 and Before
BOOM
EXTEND
PORT MAIN
RELIEF
RELIEF
VALVE
VALVE
MA0431
BOOM HOIST
PORT RELIEF
BOOM
VALVE
RETRACT
PORT RELIEF
VALVE
4. Install a tee and pressure gauge capable of
measuring 0 - 4000 psi (275,6 bar) in the
tandem pump outlet of the 30 gpm section,
Fig. 9.1.
Warning !
Before starting the engine be sure all hydraulic
connections are tight and all tools are removed
from the forklift.
5. Start the engine. Raise and lower the boom
fully several times to purge the system of air.
6. Depress the accelerator to full throttle. Place
the joystick in the "raise" position and hold until
the hoist cylinders have fully extended. Con-
tinue holding the joystick in the "raise" position
until the pressure readings are taken.
7. Check the pressure gauge reading. It should
read 2650 ± 50 psi (182,6 ± 3,4 bar). If not,
adjust the boom hoist port 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 adjust-
ment.
8. Stop the engine. Operate the hydraulic
controls after the engine has stopped to relieve
any trapped pressure.
9. Remove the pressure gauge and tee from the
tandem pump and reconnect the hydraulic line.
10. Start the engine. Raise and lower the boom
fully several times to purge the system of air.
11. Install the transmission cover after adjustment.
c. Testing
The boom raise/lower circuit should be tested when-
ever repairs or adjustments are made to components
of the circuit.
1. Start the engine, park the forklift on level
ground and level the frame.
2. Check for signs of leakage of hydraulic oil from
circuit hoses and other components. Correct
any leakage problem before testing.
3. Raise and lower the boom fully several times
to purge the system of air if necessary.
4. Starting with the boom fully retracted and at its
lowest position, raise the boom at full engine
speed. The time required for full hoist should
be 11 to 13 seconds (no load).
9-4