SECTION 6. TROUBLESHOOTING
14)Broken slow-return check valve
Disassemble and wash spool clean.
If it is damaged seriously,replace it as an
assembly.If damage is minor,correct surface
with oil stone and finish by lapping.
12)Broken flow divider
(Stuck sequential valve spool)
Inspect cylinder and valves.Replace
damaged seals,and repair.
(Check each part systematically)
11)Excessive internal leaks
Readjust.
(Cracking:refer to the specifications)
10)Maladjusted relief valve
As it will cause oil leaks or internal
wear,replace with gear oil of SAE80
9) Too low viscosity of
transmission oil
Replace8) Broken cylinder
Decrease load7) Excessive load on lift
Inspect,adjust,repair,or replace if
necessary.(Refer to section 3)
6) Poor link mechanism
Inspection pump and repair or replace if
necessary.Pay particular attention to shaft
seal because a broken seal sometimes
intakes air.
5) Broken or poor hydraulic pump
Clean.4) Clogged suction filter
Tighten securely or replace broken parts.
3) Air taken in through suction
Maintain oil level by replenishing with the
same kind of oil
2) Insufficient transmission oil
Raise engine speed slightly1) Insufficient engine speed1.Lift does
not rise
Clean them with compressed air or a sharp
point.
②Clogged orifices or slanted
orifices in pilot passage.
Lap after repairing flaws with oil stone①Stuck compensator plunger
(unloading valve 1)
13)Broken control valve
(Even when spool is shifted to up position,lift does not rise)
Lap after disassembling,cleaning, and
repairing flaws with oil stone
①Stuck poppet
Lap after repairing flaws with oil stone④Bitten or stuck check valve
plunger
Correct minor flaws with oil stone③Stuck poppet(unloading valve 2)
CountermeasuresCausesProblems
9-29
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