JLG 740AJ Service Manual - Manual (Page 300)

SECTION 5 - HYDRAULICS
5-14 – JLG Lift – 3121160
7. Using all applicable safety precautions, start the
machine from the ground control and fully raise and
lower the main boom through several cycles to
bleed the platform level hydraulic circuit.
DO NOT OPERATE THE PLATFORM LEVEL SWITCH FROM THE
PLATFORM CONTROL CONSOLE TO BLEED THE SLAVE CYLIN-
DER. A PLATFORM UPSET MAY OCCUR.
8. Check for proper operation and for hydraulic leaks.
9. Check the fluid level of hydraulic tank and adjust if
necessary.
5.7 HYDRAULIC PUMP W/HAYES PUMP
DRIVE COUPLING LUBRICATION
Any time pump or pump drive coupling is removed coat,
pump and drive coupling splines with Lithium Soap Base
Grease (TEXACO CODE 1912 OR EQUIVALENT) coupling
is greased prior to assembly.
5.8 PRESSURE SETTING PROCEDURES
Main Relief, Steer, Swing and Lift Down
FIRST: Set up the variable displacement pump
(the pump that is mounted on the back of the drive pump).
1. Stand by pressure or load sense pressure
Install a low pressure gauge at port “MP” of the
main valve block. A gauge capable of reading 400
psi (27.5 bar). Remove the wires from the upper lift
(main lift), valve coils on the main valve block. Start
the engine and activate upper lift up or down. Hold
the function for 10-15 seconds. this bleeds the air
out of the sense line. The gauge should be reading
400, +40-0 psi. (27.5, +2.7 -0 bar). To make an
adjustment to this pressure, go to the engine com-
partment, locate the variable pump. There are (2)
adjustments at the top of the pump. The stand by
adjustment is at the top. Using a 17 mm wrench,
remove the cover nut. Be careful not to lose the “o”
ring washer inside the cover nut. Loosen the jam nut
at the set screw with the 17 mm wrench. Using a 3
mm allen wrench adjust clockwise to increase, or
counterclockwise to decrease. After adjusting the
pressure, tighten the jam nut and replace the cover
nut. Reconnect the wires on the upper lift coils.
2. High pressure relief
Install a high pressure gauge at the "MP" port of the
main valve block. Activate upper (main) telescope
in. The gauge should read 2600 psi (179 bar). To
make an adjustment to this pressure, go back to the
engine compartment to the variable pump. The high
pressure relief adjustment is on the lower one of the
(2). Repeat the same procedure as setting the stand
by pressure. This is the maximum relief pressure for
all functions governed by this pump.
SECOND: Adjustments made at the main valve block.
1. Upper (main) lift down
Install a high pressure gauge at the "MP" port of the
main valve block. Activate upper lift down. The
gauge should read 1400 psi (96.5 bar). The adjust-
ment cartridge is located to the right of port #11.
Turn clockwise to increase, counterclockwise to
decrease.
2. Swing. (left and right are done with one adjustment)
Using the same gauge at the same port, lock the
turn-table lock pin. Activate swing, the gauge should
read 1400 psi (96.5 bar). The adjustment cartridge is
located on the right side of the block, the second
relief valve cartridge down from the top.
NOTE: The front of the block has the bolt on valves on that
face.) Turn clockwise to increase, and counterclock-
wise to decrease.