JLG 740A, Service And Maintenance Manual

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SECTION 3 - CHASSIS & TURNTABLE
3-30 – JLG Lift – 3121160
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 cou-
plings. 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 properly
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 condi-
tions.
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 cooling
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 applica-
ble and verify that the loads on the machine are not excessive.
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 signal
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 supply
and drain orifices are prop-
erly 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.