JLG sky trak mmv Service Manual page 191

Boom Troubleshooting (Continued)
Problem
3. Boom will not raise or lower.
4. Boom shifts to right or left
when extending.
5. Excessive boom pivot pin
noise and/or wear.
6. Excessive slave cylinder
pivot pin noise and/or wear.
7. Excessive lift/lower cylinder
pivot pin noise and/or wear.
Model MMV Rev. 12/04
Cause
1. Broken hydraulic hoses or tubes
and/or connection leaks.
2. Lift/lower hydraulic and/or
electrical system(s) not
operating properly.
3. Faulty lift/lower cylinder.
4. Seized boom pivot pin bearing.
1. Boom pivot pin improperly
shimmed.
2. Incorrect wear pad gap or
shimming, or wear pads
excessively worn.
1. Insufficient lubrication.
2. Worn bearing(s).
1. Insufficient lubrication.
2. Worn bearing(s).
1. Insufficient lubrication.
2. Worn self-aligning bearing(s).
Boom
Remedy
1. Locate break, replace hose(s)
or tube(s), tighten connections.
2. Refer to Section 9.8, Hydraulic
Circuits and Troubleshooting
and/or Section 10.7.19, Boom
Lift/Lower Circuit and
Troubleshooting .
3. Repair cylinder. Refer to Section
9.14.7, Lift/Lower Cylinder .
4. Replace bearing.
1. Re-shim the boom to a maximum
total gap of .10" (2.5 mm) with
shims distributed evenly on both
sides of the boom pivot pin.
2. Shim wear pads to correct gap.
(Refer to Section 4.3.7, a. Boom
Wear Pad Check .) Replace
wear pads as needed. (Refer to
Section 4.3.7, b. Boom Wear
Pad Replacement .)
1. Lubricate at regular intervals.
(Refer to Section 4.3.8, Boom
Lubrication Points .) Replace
worn pins as needed.
2. Replace bearing(s) and
lubricate at regular intervals.
(Refer to Section 4.3.8, Boom
Lubrication Points .)
1. Lubricate at regular intervals.
(Refer to Section 4.3.8, Boom
Lubrication Points .) Replace
worn pins as needed.
2. Replace bearing(s) and
lubricate at regular intervals.
(Refer to Section 4.3.8, Boom
Lubrication Points .)
1. Lubricate at regular intervals.
(Refer to Section 4.3.8, Boom
Lubrication Points .) Replace
worn pins as needed.
2. Replace bearing(s) and
lubricate at regular intervals.
(Refer to Section 4.3.8, Boom
Lubrication Points .)
4.47