JLG 740AJ Service Manual - Manual (Page 304)

SECTION 5 - HYDRAULICS
5-18 – JLG Lift – 3121160
3. Steer
Using 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. Platform Level Up
Install a high pressure gauge at port “M3”, located
on the right side of the block at the bottom. There is
pressure trapped at this test port. To release this
pressure, activate level down to the end of stroke
(the pressure in the up side goes to 0). This will
allow you to snap a gauge on this port. Activate level
up to the end of stroke, you should read 2600 psi
(179 bar). This is what the pump high pressure
valve is set at. We want level up to read 2800 psi
(193 bar). The level up relief valve is located in front
of the “M3” gauge port. When activating level up,
and reading 2600 psi (179 bar), turn the adjustment
counterclockwise until the pressure drops below
2600 psi (179 bar), turn clockwise (slowly) until the
gauge stops moving. It should stop at 2600 psi (179
bar), turn clockwise 1/2 turn and lock. This will give
you 2800 psi (193 bar) on level up. This pressure is
required to keep the platform level when the boom is
being lowered.
5. Platform Level Down
Install a high pressure gauge at the “M4” port
located on the left of the valve near the bottom. To
get a gauge on this point, activate level up to the
end of stroke (the pressure in the down side will go
to 0, allowing you to snap a gauge on). Activate level
down to the end of stroke, reading 1800 psi (124
bar). The level down relief valve is located on the
right side of the block above the “M4” port. Turn
clockwise to increase, and counterclockwise to
decrease.
6. Articulating Jib Up
Install a high pressure gauge on the gauge port of
the jib block located on the top of the main valve
block. The gauge port has a 12" hose plumbed into
it for easy access. Activate jib up, you should read
2500 psi (172 bar). The up relief valve is located on
the right side of the jib block toward the front. Turn
clockwise to increase, and counterclockwise to
decrease.
7. Articulating Jib Down
Install a high pressure gauge on the gauge port of
the jib block located on top of the main valve block.
The gauge port has a 12" hose plumbed into it for
easy access. Activate jib down, you should read
1200 psi (83 bar). The down relief valve is located
on the right side of the jib block toward the back.
Turn clockwise to increase, and counterclockwise to
decrease.
4 Wheel Steer (If Equipped)
1. At the platform console using the steer select switch
activate “2 wheel steer”.
2. Install a pressure gauge in port "G" on main control
valve.
3. With the aid of an assistant, activate steer left and
right, adjust front steer relief valve to 2500 PSI (172
Bar). This pressure only affects the front axle.
4. At the platform console using the steer select switch
activate “crab” or “coordinated” steer.
5. At the main control valve block disconnect the wire
din connectors on the front steer valve. When steer
is activated only the rear steer will work.
6. Install a pressure gauge in port "G" on main control
valve.
7. With the aid of an assistant, activate steer left and
right, adjust rear steer relief valve to 2500 PSI (172
Bar) Reading at the valve bank. 2500PSI (172 Bar)
will give you 2000 PSI (138 Bar) at the cylinders.
8. Re-connect the front steer din connectors at the
valve bank.
Figure 5-16. Articulating Jib Boom Pressure adjust.