JLG 740AJ, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULIC INFOR M ATION AND SCHE M ATICS
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2. High pressure relief
Install a high pressure gauge at the "MP" port of the
main valve block. Activate 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 function pump. The high pressure relief adjustment
is the lower one of the (2) on the compensator. 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
towards the engine. First, using 4 mm wrench, loosen
the setscrew on the side of compensator (facing you)
which is in line with the adjustment screw. This is the
jam nut screw which holds the main adjustment from
turning. Loosen it 1 turn. Then using the 6 mm wrench
adjust the main adjustment clockwise to increase or
counterclockwise to decrease. This is the maximum
relief pressure for all functions governed by this pump.
Adjustments Made At The Main Valve Block
1. Main lift down
Install a high pressure gauge at the "MP" port of the
main valve block. Activate main lift down. The gauge
should read 1400 psi (96.5 bar). The adjustment car-
tridge 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)
Install a high pressure gauge at the "MP" port of the
main valve block. 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. Turn clockwise to increase, counterclockwise to
decrease.
NOTE: The front of the block has the bolt on valves on that face.
3. 2 Wheel Stee r
Use the same gauge at the same port. Activate steer left
or right. The gauge should read 1800 psi. (2-wheel steer)
both directions. One relief cartridge is located on the
right side of the block, at the top. The other one is
located on the left side next to port #15. Turn clockwise
to increase, counterclockwise to decrease.
4. 4 Wheel Steer
Use the same gauge at the same port. Activate front
wheel steer left or right. One relief cartridge is located
on the right side of the block, at the top. The other one is
located on the left side next to port #15. Turn clockwise
to increase, counterclockwise to decrease. Adjust both
reliefs to 2600 psi. Remove the coils from the front wheel
directional valve. Activate 4 wheel steer. Adjust the rear
wheel steer reliefs to 2600 psi. Those reliefs are located
on the 4 wheel steer block bolted on the front of the
main control valve.