JLG 1850SJ Service Manual - Manual (Page 261)

SECTION 5 - BASIC HYDRAULIC INFORMATION & HYDRAULIC SCHEMATICS
3121619 – JLG Lift – 5-91
Troubleshooting
EXCESSIVE NOISE OR VIBRATION
SLOW ACTUATOR RESPONSE
Item Description Action
Check fluid in reservoir. Insufficient hydraulic fluid causes cavitation. Fill reservoir to proper level.
Check for air in system. Air in system causes noisy, erratic control. Purge air and tighten fittings. Check inlet for leaks.
Check pump inlet pressure/vacuum. Improper inlet conditions cause erratic behavior and low
output flow. Correct pump inlet pressure /vacuum conditions.
Inspect shaft couplings. A loose or incorrect shaft coupling causes excessive noise
and/or vibration. Repair or replace coupling. Ensure correct coupling is
used.
Check shaft alignment. Misaligned shafts create excessive noise and/or vibra-
tion. Correct shaft misalignment.
Hydraulic fluid viscosity above acceptable limits. Hydraulic fluid viscosity above acceptable limits or low
fluid temperature will not allow pump to fill or control to
operate properly. Allow system to warm up before operating, or use fluid
with appropriate viscosity grade for expected operating
temperatures.
Item Description Action
Check external system relief valve
setting. Low external relief valve setting slows down system. Adjust external relief valve setting following manufac-
turer’s recommendations. External relief setting must be
above PC setting to operate properly.
Check PC and LS control setting. Low PC setting prevents the pump from achieving full
stroke. Low LS setting limits output flow. Adjust PC and LS setting.
Check LS control signal pressures. Incorrect LS signal will not allow pump to operate cor-
rectly. Inspect system to ensure that proper LS signal transmit to
pump.
Internal system leaks. Worn internal parts don’t allow pump to operate prop-
erly. Refer to Authorized Service Center for required repair.
Hydraulic fluid viscosity above
acceptable limits. Hydraulic fluid viscosity above acceptable limits or low
fluid temperature will not allow the pump to fill or con-
trol to operate properly. Allow system to warm up before operation or sue fluid
with the appropriate viscosity grade for expected operat-
ing temperatures.
Check external system valving. Malfunctioning valving may not allow system to respond
properly. Repair or replace system valving as required.
Check pump case pressure. High case pressure causes the system to be sluggish. Correct case drain line restrictions.
Check pump inlet pressure/vacuum. High inlet vacuum causes low output flow. Correct inlet pressure conditions.