JLG 740AJ, Service And Maintenance Manual

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SECTION 4 - BOO M & PLATFOR M
4-20 3121160
Installation
1. Using a suitable lifting device, position the tower boom
such as to align upright leveling cylinder with attach
holes in tower boom. Using a soft head mallet, install the
cylinder pin into tower boom and secure with mounting
hardware.
2. Using a suitable lifting device, position boom assembly
on turntable so that the pivot holes in both boom and
turntable are aligned.
3. Install boom pivot pin, ensuring that location of hole in
pin is aligned with attach point on turntable.
4. If necessary, gently tap pin into position with soft
headed mallet. Secure pin mounting hardware.
5. Connect all wiring connectors to the correct connectors.
6. Connect all hydraulic lines of boom assembly.
7. Using all applicable safety precautions, operate lifting
device in order to position tower boom lift cylinder so
that holes in the cylinder rod end and boom structure
are aligned. Insert the lift cylinder pin, ensuring that
location of hole in pin is aligned with attach point on
boom.
8. Install the main boom assembly. Refer to Section 4.6,
Main Boom Assembly.
9. Install the upright. Refer to Section 4.7, Upright.
10. Using all applicable safety precautions, operate from the
lower controls and raise boom fully, noting the perfor-
mance. Lower the boom, noting the performance.
Tower Out of Sync
Tower is out of sync backwards, upright leaning toward the
platform.
When towering down the upright cylinder bottoms out before
the lower lift. Problems that could cause this are:
1. The releveling valve (red knob on the oil tank P/N:
4640866), this is a poppet valve that could be leaking
fluid out of the closed loop. Manually opening the valve
and flushing it can eliminate any contaminate on the
seat. The seat could also be damaged, so replacing the
cartridge might be necessary.
2. A relief valve is located in the upright (P/N: 4640929).
This relief valve could be leaking backwards out of the
loop. Replace the cartridge. They are pre-set.