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2.4 Hydraulic system fault diagnosis and correction
Fault Probable cause Corrective action
No oil
pumps from
the pump
Low oil level Fill to the specified oil level
Blocking of strainer
Clean oil pipe and oil tank. If hydraulic oil is
dirty, please change it.
Low oil
pressure of
oil pump
output
Bearing worn; retainer, O-ring
damage
Change the bad spare parts
Adjustment failure of safety
valve
Rise pressure with pressure gage
Air in the oil pump
Fill hydraulic oil to the oil tank, use the pump
after bubble vanishing
Noise of oil
pump
Cavitation arising from the
strainer blocking
Adjust or replace soft tube and clean the
strainer
Cavity caused by the high
viscosity of hydraulic oil
Replace new hydraulic oil, whose viscosity
suits pump running speed. Work only when the
oil temperature is normal
Bubble in the hydraulic oil
Check the reason for the bubble and then take
measures
Forks can
’
t lift
Gear
pump
works
Oil way block or damage Repair or replace
Gear
pump
no work
Lifting inching switch loosen or
damage
Re-fix or replace
Motor or circuit fault Repair
Forks do not
drop down
Solenoid valve block or
damage
Repair or replace
Pressure of
safety valve
is unstable
or can’t be
adjusted
Pressure adjusting screw
loosen
Re-adjust and lock.
Pressure adjusting spring
deformation or damage.
Replace
Safety valve spool wear or
sticking
Replace or clean to reassemble.
Pump failure Repair pump
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