Testing And Adjusting
Troubleshooting
Below table lists the difficulties which may be
experienced with the unit and the hydraulic system. It
indicates the cause and remedy for each of the
trouble listed. It should always be remembered that
pressure and delivery are factors which are usually
dependent upon each other. Adequate pressure
gauge equippment and a thorough understanding of
the operation of the complete hydraulic system are
essential to diagnose improper conditions.
22 of 29
New Hydraulic Systems
Testing and Adjusting
Trouble :
Oil leaks at either end of spools.
Probable Cause
Defective O-rings in valve
body
Remedy
Replace O-rings
Trouble :
Spring-centered spools do not return to neutral.
Probable Cause
Broken springs
Bent spool
Foreign particles
Misalignment of operating
linkage
Valve bank improperly
torqued
Probable Cause
Worn detent barrel
Weak or broken detent
spring
Remedy
Replace springs
Replace with new section of
same size and type
Clean system and valve
Check linkage for binding
condition
Retorque nuts to specified
ratings
Remedy
Replace detent barrel
Replace detent spring
Trouble :
Detent type spools will not stay in detent position
Trouble :
No motion, slow or jerky action of hydraulic system
Probable Cause
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 stroke
Remedy
Repair, clean and readjust
Disassemble, clean and
reassemble
Replace valve section
Check travel
Trouble :
No relief valve action (high pressure)
Probable Cause
Small particle of dirt plugging
orifice in relief valve sub-
assembly
Relief valve sub-assembly
installed backward
Remedy
Remove relief valve and
check hole. If blocked, clear
hole
Install properly
Trouble :
Load will not hold
Probable Cause
Oil by passing between spool
and body
Oil by passing piston in cylinder
Cylinder not centered
Remedy
Replace valve
Repair or replace cylinder
Refer to above spool remedies
Trouble :
Load drops when spool is moved from neutral to a
power position
Probable Cause
Dirt or foreign particles lodged
between check valve ball and seat
Scoreed or sticking check valve
Remedy
Disassemble, clean and
reassemble
Replace poppet
Summary of Contents for D20S-2
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