Group 30, Hydraulic Control Valve/Lift Circuit
30-3-2 • Hydraulic System Troubleshooting SM 765, Nov ’06
Spring-centered spools do not return to
neutral
• Broken springs; rebuild valve.
• Entrapped foreign particles; check and clean sys-
tem and valve.
• Bent spool; replace with new valve section.
• Misalignment or binding of linkage; check and
align/adjust linkage.
No relief valve action (high pressure)
• Small particles of dirt in relief valve subassembly;
check, clean, and/or replace relief valve, clean
hole.
• Relief valve subassembly installed backwards;
reinstall correctly.
Load drops when spool is moved from
neutral to lift position
• Dirt or foreign particles lodged between check
valve ball and seat; check and clean.
• Sticking or scored check valve; clean if sticking,
replace if scored, replace poppet.
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