Service Manual
Series 45 J Frame Open Circuit Axial Piston Pumps
520L0607
• Rev AI • Sep 2013
19
Troubleshooting
(continued)
System Operating Hot
Low Pump Output Flow
Pressure or Flow Instability
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 temperature for
the heat exchanger.
Insufficient air flow, high input air
temperature, or undersized heat
exchanges 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 following manufacturer’s
recommendations. External relief
valve setting must be above PC
setting for proper operation.
Check pump inlet pressure/vacuum. High inlet vacuum adds heat to
system.
Correct inlet pressure/vacuum
conditions.
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 temperature will
not allow the pump to fill or control
to operate properly.
Allow system to warm up before
operating, or use fluid with the
appropriate viscosity grade for
expected operating temperatures.
See
Hydraulic Fluids and Lubricants
Technical Information Manual,
520L0463
.
Check external system relief valve
setting.
Eternal relief valve set below PC
setting causes low output flow.
Adjust external relief valve
following manufacturer’s
recommendation. External relief
valve 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.
Adjust PC and LS setting. Refer to
Adjustment
, page 21.
Check pump inlet pressure/vacuum. High inlet vacuum causes low
output flow.
Correct inlet pressure conditions.
Check input speed.
Low input speeds decrease flow.
Adjust input speed.
Check pump rotation.
Incorrect rotational configuration
causes low flow.
Use pump with appropriate
rotational configuration.
Item
Description
Action
Check for air in system.
Air in system causes erratic
operation.
Activate PC allowing system to
bleed air. Check inlet line for leaks
and eliminate source of air
ingression.
Check control spools.
Sticking control spools cause erratic
operation.
Inspect spools for free movement in
bore. Clean or replace.