14
F. Troubleshooting
Table 4 lists the difficulties which may be experienced with
the unit and hydraulic system. It indicates the cause and
remedy for each of the troubles listed. It should always be
remembered that pressure and delivery are factors which
are usually dependent upon each other. Adequate pressure
gage equipment and a thorough understanding of the
operation of the complete hydraulic system are essential to
diagnose improper operation.
TROUBLE
PROBABLE CAUSE REMEDY
Oil leads at either end of spool Defective O-rings in valve body
Broken springs
Bent spool
Foreign particles
Misalignment of operating linkage
Valve tank improperly torque
Replace O-rings.
Replace springs.
Replace with new section of same size
and type.
Clean system and valve,
Check linkage for binding condition.
Re-torque nuts to specified ratings.
Detent type spools will not stay in
detent position
Worn detent barrel
Weak or broken detent spring
Replace detent barrel.
Replace detent spring.
No motion, slow or jerky action of
hydraulic system
Relief valve not properly set, or stuck in
base and/or worn
Dirt or foreign particles lodged between
relief valve control poppet and seat
Valve body cracked inside
Spool not moved to full stoke
Repair, clean and readjust.
Disassemble, clean and reassemble.
Replace valve section.
Check travel.
No relief valve action
(High Pressure)
Small particle of dirt plugging orifice in
relief valve sub-assembly
Relief valve sub-assembly installed
backwards.
Remove relief valve and check hole. If
blocked, clear hole.
Install properly.
Load will not hold Oil by-passing between spool and body
Oil by-passing piston in cylinder
Spool not centered
Replace valve.
Repair or replace cylinder.
Refer to above spool remedies.
Load drops when spool is moved
from neutral to a power position
Dirt or foreign particles lodged between
check valve poppet and seat.
Scored or sticking check valve poppet
Disassemble, clean and reassemble.
Replace poppet.
Table 4. Troubleshooting Chart
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