JLG 680S, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULICS INFORMATION & SCHEMATICS
3121234 5-49
Troubleshooting
Table 5-8. Excessive Noise and/ or Vibration
Item Description Action
Check fluid level in reservoir. Insufficient hydraulic fluid will cause cavitation. Fill the reservoir to proper level.
Check for air in system. Air in system will cause noisy, erratic control. Purge air and tighten fittings. Check inlet for leaks.
Check pump inlet pressure / vacuum. Improper inlet conditions will cause erratic behavior and
low output flow. Correct pump inlet pressure / vacuum conditions. Refer to
Hydraulic parameters.
Inspect shaft couplings. A loose or incorrect shaft coupling will cause excessive
noise and/or vibration. Repair or replace coupling and ensure that correct coupling
is being used.
Check shaft alignment. Misaligned shafts will 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 the pump to fill or control
to operate properly. Allow system to warm up before operation or use fluid with
the appropriate viscosity grade for expected operating
temperatures.
Table 5-9. Actuator Response is Sluggish
Item Description Action
Check external system relief valve setting. Low external relief valve setting will slow down system. Adjust external relief valve setting per manufacturer’s rec-
ommendations. External relief setting must be above Pres-
sure Compensator setting for proper operation.
Check Pressure Compensator and LS control setting. Low Pressure Compensator setting will prevent the pump
from achieving full stroke. Low Load Sense setting will
limit output flow. Adjust Pressure Compensator and Load Sense setting.
Refer to Adjustments.
Check Load Sense control signal pressures. Incorrect Load Sense signal will not allow pump to operate
correctly. Inspect system, ensure that proper Load Sense signal is
transmitted to the pump.
Internal system leaks. Worn internal parts will not allow the pump to operate
properly. Refer to Authorized Service Center for repairs as required.
Hydraulic fluid viscosity above acceptable limits. Hydraulic fluid viscosity above acceptable limits or low
fluid temperature will not allow the pump to fill or control
to operate properly. Allow system to warm up before operation or use fluid with
the appropriate viscosity grade for expected operating
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 will cause the system to be sluggish. Correct case drain line restrictions.
Check pump inlet pressure / vacuum. High inlet vacuum will cause low output flow. Correct inlet pressure conditions.