JLG 660SJ Service Manual - Manual (Page 71)

SECTION 3 - CHASSIS & TURNTABLE
3121202 – JLG Lift – 3-21
Troubleshooting
Table 3-3. Excessive Noise and/or Vibration
Item Description Action
Check oil level in reservoir
and oil supply to the motor. Insufficient hydraulic fluid could lead to cavitation that would
cause system noise.
Fill the reservoir to the proper level and ensure that oil supply
to the motor is adequate and the lines are unobstructed.
Check for air in the system.
Air trapped within the system lines, or the motor itself, could
result in cavitation that would cause system noise.
Ensure that all of the system lines and components are
purged of air.
Inspect the output shaft
couplings. A loose or incorrect shaft coupling will produce vibrations
that could result in system noise.
Ensure that the correct coupling is used and that it fits prop-
erly onto the shaft.
Inspect the output shaft
alignment. Misaligned shafts create excessive frictional vibration that
could result in system noise. Ensure that the shafts are properly aligned.
Hydraulic oil viscosity
above limits. Viscosity above acceptable limits will result in cavitation that
would lead to system noise. Replace hydraulic oil with appropriate fluid for operating
conditions.
Table 3-4. System Operating Hot
Item Description Action
Check oil level in reservoir
and oil supply to the pump. Insufficient amount of hydraulic fluid will not meet the cool-
ing demands of the system. Fill the reservoir to the proper level.
Inspect the heat exchanger,
(if so equipped). If the heat exchanger fails, or becomes obstructed, it may
not meet the cooling demands of the system.
Ensure that heat exchanger is receiving adequate air flow
and that the heat exchanger is in good operating condition.
Repair or replace as necessary.
Check the system relief
valves.
If a system relief valve becomes unseated for an extended
period of time or fails for any other reason, the system could
become overheated.
Repair or replace any malfunctioning relief valves as appli-
cable and verify that the loads on the machine are not exces-
sive.
Table 3-5. Won’t Shift or Slow to Start
Item Description Action
Check the signal line to the
servo control port.
Obstructed or restricted flow through the servo control sig-
nal lines could result in slow shift or no shift conditions
within the motor. Ensure that the signal lines are not obstructed or restricted
and that signal pressure is adequate to shift the motor.
Check that the correct sup-
ply and drain orifices are
properly installed, and are
not obstructed.
Supply and drain orifices determine the shift rate of the
motor. The smaller the orifice, the longer the time it takes to
shift the motor. Obstruction will also increase shift times.
Ensure that the proper control orifices are installed in the
motor and verify that they are not obstructed. Clean or
replace as necessary.