JLG 800S Service Manual - Manual (Page 281)

SECTION 5 - HYDRAULICS
3121139 – JLG Lift – 5-11
5.3 PRESSURE SETTING PROCEDURE
Cold temperatures have a significant impact on pressure
readings. 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 readings are acceptable if they are within
± 5% of specified pressures.
To ensure all pressures are set correctly, the following pro-
cedures must be followed in order.
1. All applicable steps in Section 5.4, Start Up Proce-
dures must be followed.
2. Set up of the function pump.
3. Adjustments made at the main valve block.
4. Adjustments made at the platform valve.
Set Up of the Function Pump
STAND BY PRESSURE OR LOAD SENSE PRESSURE
1. Install a low pressure gauge at port “M1” of the main
valve block. A low pressure gauge capable of read-
ing 500 psi.
2. Start the engine from the ground control. The gauge
should read between 400-440 psi (27.5 to 30 Bar).
To make an adjustment to this pressure, go to the
engine compartment, locate the function pump.
3. There are (2) adjustments at the top of the pump.
They are located on the pump compensator which
has (4) bolts mounting it to the pump. The stand by
adjustment is at the top. To adjust this, a 4 mm and 6
mm allen wrench will be needed. The adjustment
screw is facing the front of the pump, or toward the
engine.
a. First, using the 4 mm wrench, loosen the set
screw on the side of the compensator (facing
you) which is in line with the adjustment screw.
This is a jam nut screw which holds the main
adjustment from turning. Loosen it 1 turn.
b. Next, using the 6 mm wrench adjust the main
adjustment clockwise to increase or counter-
clockwise to decrease. The pressure should
read between 400-440 psi (27.5 to 30 Bar).