Greenlee / A Textron Company 18 4455 Boeing Dr. • Rockford, IL 61109-2988 USA • 815-397-7070
980 Hydraulic Power Pump
Troubleshooting—Pilot-Operated Valve (cont’d)
Pilot-operated valve will A particle of dirt or some other foreign Disassemble, clean and inspect the
not close. (cont’d) object is holding the low-pressure valve piston (48), spring (47), ball (46),
relief valve open. spring (45) and stem (44).
Replace parts as necessary.
Low-pressure relief valve is set too low. See Low-Pressure Relief Setting,
Figure A4 in the Repairs section of this
manual.
Low-pressure bypass check ball seat is See Ball Seat Refinishing in the Repairs
damaged. section of this manual. Figures B2, B3,
and B4.
Low-pressure bypass check seat is Replace the pump block (84).
oversized.
The pilot piston does not advance freely.
See Hydraulic Schematic (7).
See Low-Pressure Relief Setting,
Figure A4 in the Repairs section of this
manual. Clean and inspect items 42-49.
Replace parts as necessary.
Valve seat is damaged. See Hydraulic Schematic (3, 7).
PROBLEM PROBABLE CAUSE POSSIBLE REMEDY
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