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JCB JS70 Hydraulic Pump Fault finding

Hydraulic Pump Fault finding

  1. As a first step towards locating a fault, carry out the following checks.
  2. Check the hydraulic filter for the presence of excessive foreign materials. The nature of the foreign materials could yield a clue as to the source of damage or wear.
  3. Check the flow rate and condition of the oil drained from the pump.
  4. Check for abnormal sounds and vibration.
  5. Check the pressure at each of the pump pressure test points
Symptom Possible cause Remedy
1 Pump is producing abnormal noise.   Air is being drawn in due to low oil level in the hydraulic oil tank.

Pump cavitation due to a clogged suction strainer.

Excessively low oil temperature, or pump cavitation due to high oil viscosity.

Input shaft rotation speed abnormally high.

Component mechanically damaged, Bearing etc.

Top up the hydraulic oil and bleed air from the system.

Clean the strainer. If excessively clogged, flush the hydraulic system and/or renew the hydraulic oil.

Check that the correct hydraulic oil for the ambient conditions is being used. If not, renew the oil.

Adjust the rotation speed.

Replace the damaged parts Reset the pressure. Flush the circuit. Change the hydraulic oil.

2 Insufficient flow. Input shaft rotation speed decrease.

Oil temperature abnormally high.

Oil viscosity abnormally high.

Switching valve or actuator leakage.

Inadequate pump displacement.

Power adjustment screw is loose.

Air is being drawn in due to low oil level in the hydraulic oil tank.

Pump cavitation due to a clogged suction strainer.

Excessively low oil temperature, or pump cavitation due to high viscosity.

Adjust the rotation speed. Stop the operation and re-check after the oil temperature has dropped.

Check that the correct hydraulic oil for the ambient conditions is being used. If not, renew the oil.

Replace the switching valve and actuator.

Replace the pump.

Reset and lock.

Top up the hydraulic oil and bleed air from the system.

Clean the strainer. If excessively clogged, flush the hydraulic system and/or renew the hydraulic oil.

Check that the correct hydraulic oil for the ambient conditions is being used. If not, renew the oil.

3 Pressure does not increase. Relief valve is set low.

Switching valve or actuator leakage.

Inadequate pump displacement.

Reset the relief valve.

Replace the switching valve actuator.

Replace the pump.

4 Overload at static load. Pump horsepower settings

Fault on control devise.

Component mechanically damaged, Bearing etc.

Reset the pump.

Fix damage caused by foreign matter or replace the pump.

Replace the damaged parts Reset the pressure.

Flush the circuit.

Change the hydraulic oil.

5 Rotation speed low in dynamic load.   Peak pressure occurs due to decrease in responsiveness of the relief valve.

Decrease in responsiveness of the control device.

Check for abnormal vibration of the circuit and measure pressure, if found replace the relief valve.

Check for foreign matter clogging the servo line. If found remove the foreign matter.

Check for debris on each sliding part of the control devices.

Fix the damage caused by the foreign matter.

6 Pump produces abnormal heat. Increase in pump leakage.

Component mechanically damaged, Bearing etc. Seizure or wear of pump internal parts.

Measure actuator speed, replace pump.

Replace the damaged parts Reset the pressure.

Flush the circuit/change the hydraulic oil.

Replace damaged parts or pump.

7 Oil leakage    Damage to o-rings or seals, confirm the oil leakage points and measure for abnormal pressure.

Damage to oil seal, check for damage due to foreign matter and measure for abnormal pressure.

Wear of seal due to contact with input shaft.

Loose plugs.

Replace damaged seals.

Replace damaged seals.

Replace input shaft or pump.

Tighten plugs or replace seals.

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