Oshkosh Corporation JLG 450AJ, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
3121659 – JLG Lift – 5-33
5.2 PRESSURE SETTING PROCEDURE
Cold temperatures have a significant impact on pressure read-
ings. JLG Industries Inc. recommends operating the machine
until the hydraulic system has warmed to normal operating
temperatures prior to checking pressures. JLG Industries Inc.
also recommends the use of a calibrated gauge. Pressure read-
ings are acceptable if they are within ± 5% of specified pres-
sures.
To ensure all pressures are set correctly, the following proce-
dures must be followed.
Main System Relief
1. Install a pressure gauge at port MP1 of the Main Control
Valve capable of reading pressures up to 4000 psi (275
Bar).
2. Activate telescope in function continuously at end of
stroke. Pressure that is observed should be 3000 ± 75 psi
(207 ± 6 Bar).
3. If necessary, loosen jam nut and adjust the Main System
Relief valve clockwise to increase and counter-clockwise
to decrease.
Steer Left Relief
1. Install a pressure gauge at port MP1 of the Main Control
Valve capable of reading pressures up to 4000 psi (275
Bar).
2. Activate Steer Left function continuously at end of
stroke. Pressure that is observed should be 2750 ± 75 psi
(190 ± 6 Bar).
3. If necessary, loosen jam nut and adjust the Steer Left
Relief valve clockwise to increase and counter-clockwise
to decrease.
NOTE: Steer left pressure at port 24 is 2500 psi (173 Bar); a gauge
may be placed there for troubleshooting.
Steer Right Relief
1. Install a pressure gauge at port MP1 of the Main Control
Valve capable of reading pressures up to 4000 psi (275
Bar).
2. Activate Steer Right function continuously at end of
stroke. Pressure that is observed should be 2750 ± 75 psi
(190 ± 6 Bar).
3. If necessary, loosen jam nut and adjust the Steer Right
Relief valve clockwise to increase and counter-clockwise
to decrease.
NOTE: Steer Right pressure at port 23 is 2500 psi (173 Bar); a
gauge may be placed there for troubleshooting.
Swing Relief
1. Install a pressure gauge at port MP1 of the Main Control
Valve capable of reading pressures up to 3000 psi (207
Bar).
2. Activate Boom Swing Right or Left function continu-
ously against the stop or lock. Pressure that is observed
should be 1800 ± 50 psi (125 ± 4 Bar).
3. If necessary, loosen jam nut and adjust the Boom Swing
Relief valve clockwise to increase and counterclockwise
to decrease.
NOTE: Boom Swing Right pressure at port 15 and Boom Swing
Left pressure at port 16 is 1700 psi (117 Bar); a gauge may
be placed there for troubleshooting.
Jib Lift Down Relief
1. Install a pressure gauge at port M34 of the Fly Boom
Control Valve capable of reading pressures up to 3000
psi (207 Bar).
2. Activate Jib Lift Down function continuously at end of
stroke.
3. Pressure that is observed should be 1500 ± 50 psi (104 ±
4 Bar).
4. If necessary, loosen jam nut and adjust the Jib Lift Down
Relief valve clockwise to increase and counter-clockwise
to decrease.
Platform Level Up Relief
The Platform Level Up relief is preset and does not normally
need checked or adjusted. If necessary, the following proce-
dure may be utilized for troubleshooting purposes:
1. With the tower boom fully lowered, lift the main boom
up several degrees from the fully lowered position.
Ensure that there is still access to the level cylinder.
2. Remove the hose from the Level Up port of the Level
Cylinder (V1 Port) - Install a pressure gauge capable of
reading pressures up to 4000 psi (275 Bar) onto this hose
and cap or plug the port in the Level Cylinder
3. Activate Main Boom Lift Down function using Axillary
Mode continuously until fully lowered.
4. Pressure that is observed should be 3400 ± 85 psi (234 ±
6 Bar).
5. If necessary, loosen jam nut and adjust the Platform
Level Up Relief valve clockwise to increase and counter-
clockwise to decrease.
6. Remove the gauge and reinstall the hose.