Item
Description
Action
System pressure
Low system pressure does not provide enough power to
move load.
Measure system pressure. Continue to next step.
System relief valves
Defective high pressure relief valves cause slow system
pressure.
Repair or replace high pressure relief valves.
Input to control
Input is operating improperly.
Repair/replace control.
System noise or vibration
Item
Description
Action
Reservoir oil level
Low oil level leads to cavitation.
Fill reservoir.
Aeration of the oil/pump
inlet vacuum
Air in system decreases efficiency of units and controls. Air
in system is indicated by excessive noise in pump, foaming
in oil, and hot oil.
Find location where air is entering into the system and
repair leak. Check that inlet line is not restricted and is the
proper size.
Cold oil
If oil is under cold conditions, it may be too viscous for
proper function and pump cavitates.
Allow the oil to warm up to it’s normal operating
temperature with engine at idle speed.
Pump inlet vacuum
High inlet vacuum causes noise/cavitation.
Check that inlet line is not restricted and is the proper size.
Check filter and bypass valve.
Shaft couplings
A loose shaft coupling will cause excessive noise.
Replace loose shaft coupling. Replace pump shaft.
Shaft alignment
Misaligned shafts creates noise
Align shafts.
Charge/system relief valves
Unusual noise may indicate sticking valves. Possible
contamination.
Clean/replace valves and test pump. May be a normal
condition.
Neutral Difficult or Impossible to Find
Item
Description
Action
Input to pump control
Input to control module is operating improperly.
Disconnect input and check to see if pump comes back to
neutral. If Yes, input fault, replace/repair external
controller. If No, go to next step.
Pump control neutral
Neutral set improperly.
Shunt servo gauge ports M4 and M5 together with
external hose and see if pump comes back to neutral. If
Yes: control neutral improperly set. If no: balance
theswashplate (see
Mechanical/hydraulic neutral
adjustment
). If you still cannot set neutral, replace the
control.
Sluggish System Response
Item
Description
Action
Oil level in reservoir
Low oil level causes sluggish response.
Fill reservoir.
High pressure relief valves/
pressure limiter settings
Incorrect pressure settings affects system reaction time.
Adjust or replace high pressure relief valves.
Low prime mover speed
Low engine speed reduces system performance
Adjust engine speed.
Charge pressure
Incorrect pressure affects system performance
Measure and adjust charge pressure relief or replace charge
pump.
Air in system
Air in system produces sluggish system response
Fill tank to proper level. Cycle system slowly for several
minutes to remove air from system.
Contaminated control
orifices
Control orifices are plugged.
Clean control orifices.
Pump inlet vacuum
Inlet vacuum is too high resulting in reduced system
pressure.
Measure charge inlet vacuum. Inspect line for proper sizing.
Replace filter. Confirm proper bypass operation.
Service Manual
MP1
Troubleshooting
©
Danfoss | April 2019
AX00000244en-000201 | 45
