JLG 680S, Service And Maintenance Manual

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SECTION 5 - BASIC HYDRAULICS INFORMATION & SCHEMATICS
5-50 3121234
Table 5-10. System Operating Hot
Item Description Action
Check fluid level in reservoir. Insufficient volume of hydraulic fluid will not meet cooling
demands of system. Fill reservoir to proper level. Verify proper size of reservoir.
Inspect heat exchanger. Check air flow and input air tem-
perature for the heat exchanger. Insufficient air flow, high input air temperature, or under-
sized heat exchanger will not meet cooling demands of the
system. Clean, repair, or replace heat exchanger as required. Verify
proper size of heat exchanger.
Check external system relief valve setting. Fluid passing through relief valve adds heat to system. Adjust external system relief valve setting per manufac-
turer’s recommendations. External relief valve setting
must be above Pressure Compensator setting for proper
operation.
Check pump inlet pressure / vacuum. High inlet vacuum adds heat to system. Correct inlet pressure / vacuum conditions.
Table 5-11. Low Pump Output Flow
Item Description Action
Check fluid level in reservoir. Insufficient hydraulic fluid will limit output flow and cause
internal damage to pump. Fill the reservoir to proper level.
Hydraulic fluid viscosity above acceptable limits. Fluid viscosity above acceptable limits or low fluid tem-
perature 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 relief valve setting. External relief valve set below Pressure Compensator set-
ting will cause low output flow. Adjust external relief valve per manufacturer’s recommen-
dation. External relief valve setting must be above Pressure
Compensator setting for proper operation.
Check Pressure Compensator and Load Sense control set-
ting. 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 pump inlet pressure / vacuum. High inlet vacuum will cause low output flow. Correct inlet pressure conditions.
Check input speed. Low input speeds decrease flow. Adjust input speed.
Check pump rotation. Incorrect rotational configuration will cause low flow. Use pump with appropriate rotational configuration.