SECTION 4 - HYDRAULICS
3121642 – JLG Lift – 4-21
Pressure Setting Procedures
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.
1. Main Relief
a. Refer to Figure 4-16., Main Valve Block.
b. Locate the lift up solenoid valve. Remove the coil
nut and remove the coil from the cartridge. Do not
remove the wire out of the coil plug.
c. Install a pressure gauge, 3000 psi (207 bar) or higher,
at port MP1. Start the engine and activate lift up.
d. Gauge should read 3000 psi (207 bar).
e. Adjust the main relief (RV2) clockwise to increase,
counter-clockwise to decrease.
f. Reintall the coil to the cartridge and torque to 5 lb-ft
(6.8 Nm).
2. Lift Up Relief Valve
a. Refer to Figure 4-16., Main Valve Block.
b. Install a pressure gauge, 3000 psi (207 bar) or higher,
at port MP1. Start the engine and activate lift up.
c. Gauge should read 2700 psi (186 bar).
d. Adjust the lift up relief (RV1) clockwise to increase,
counter-clockwise to decrease.
3. Steer Relief Valve
a. Refer to Figure 4-16., Main Valve Block.
b. Install a pressure gauge, 3000 psi (207 bar) or higher,
at port MS. Start the engine and activate steer right
or left.
c. Gauge should read 2500 psi (172 bar).
d. Adjust the steer relief (RV3) clockwise to increase,
counter-clockwise to decrease. This relief valve
takes care of both right and left.
4. Leveling Jack Retract Relief Valve
a. Refer to Figure 4-16., Main Valve Block.
b. Install a pressure gauge, 3000 psi (207 bar) or higher,
at port MP1. Start the engine and activate jack
retract.
c. When all jacks are retracted the gauge should read
2500 psi(172 bar).
d. Adjust the relief valve located on the leveling jack
directional valve (refer to Figure 4-19.) clockwise to
increase, counter-clockwise to decrease. (The relief
valve is on the same face as the solenoid valves).
5. Single Power Deck Relief Valve
a. Refer to Figure 4-20., Powerdeck Valve (Single).
b. A pressure gauge must be hosed in the power deck
retract circuit. Tee the gauge in port 2 of the power
deck valve.
c. Retract the power deck. Gauge should read 1500 psi
(103 bar).
d. Adjust the relief valve (RV1) clockwise to increase,
counter-clockwise to decrease.
NOTE: This type of relief valve is a bi-directional type. Port 2 is the
primary setting. Port 1 is the secondary setting. Port 1 is a
function of Port 2. When setting the primary setting, the
secondary setting can be as much as 300 psi (21 bar) lower.
In order to check Port 1, tee in a gauge at Port 1.
6. Dual Power Deck Relief Valve
Front Power Deck:
a. Refer to Figure 4-21., Powerdeck Valve (Double).
b. A pressure gauge must be hosed in the power deck
retract circuit. Tee in a gauge at Port 4 of the dual
deck valve.
c. Retract the power deck. Gauge should read 1500 psi
(103 bar).
d. Adjust the relief valves (RV1, RV2) clockwise to
increase, counter-clockwise to decrease.
NOTE: This type of relief valve is a bi-directional type. Port 4 is the
primary setting. Port 3 is the secondary setting. Port 3 is a
function of Port 4. When setting the primary setting, the
secondary setting can be as much as 300 psi (21 bar) lower.
In order to check Port 3, tee in a gauge at Port 3.
Rear Power Deck:
a. Refer to Figure 4-21., Powerdeck Valve (Double).
b. A pressure gauge must be hosed in the power deck
retract circuit. Tee in a gauge at Port 2 of the dual
deck valve.
c. Retract the power deck. Gauge should read 1500 psi
(103 bar).
d. Adjust the relief valves (RV1, RV2) clockwise to
increase, counter-clockwise to decrease.
NOTE: This type of relief valve is a bi-directional type. Port 2 is the
primary setting. Port 1 is the secondary setting. Port 1 is a
function of Port 2. When setting the primary setting, the
secondary setting can be as much as 300 psi (21 bar) lower.
In order to check Port 1, tee in a gauge at Port 1.
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