SECTION 6. TROUBLESHOOTING
Problems Causes Countermeasures
1.Lift does
not rise
1) Insufficient engine speed Raise engine speed slightly
2) Insufficient transmission oil Maintain oil level by replenishing with the
same kind of oil
3) Air taken in through suction
Tighten securely or replace broken parts.
4) Clogged suction filter Clean.
5) Broken or poor hydraulic pump Inspection pump and repair or replace if
necessary.Pay particular attention to shaft
seal because a broken seal sometimes
intakes air.
6) Poor link mechanism Inspect,adjust,repair,or replace if
necessary.(Refer to section 3)
7) Excessive load on lift Decrease load
8) Broken cylinder Replace
9) Too low viscosity of
transmission oil
As it will cause oil leaks or internal
wear,replace with gear oil of SAE80
10)Maladjusted relief valve Readjust.
(Cracking:refer to the specifications)
11)Excessive internal leaks Inspect cylinder and valves.Replace
damaged seals,and repair.
(Check each part systematically)
12)Broken flow divider
(Stuck sequential valve spool)
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.
13)Broken control valve
(Even when spool is shifted to up position,lift does not rise)
①Stuck compensator plunger
(unloading valve 1)
Lap after repairing flaws with oil stone
②Clogged orifices or slanted
orifices in pilot passage.
Clean them with compressed air or a sharp
point.
③Stuck poppet(unloading valve 2)
Correct minor flaws with oil stone
④Bitten or stuck check valve
plunger
Lap after repairing flaws with oil stone
14)Broken slow-return check valve
①Stuck poppet
Lap after disassembling,cleaning, and
repairing flaws with oil stone
9-33
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