Greenlee TZ Serie Manuel D'instructions page 15

Troubleshooting—Pilot-Operated Valve (cont'd)
Problem
Pilot-operated valve will not close.
Greenlee Tools, Inc.
Probable Cause
A particle of dirt or some other
foreign object is holding the low-
pressure bypass check valve open.
Low-pressure bypass check valve is
faulty.
The ball seat of the low-pressure
bypass check valve is damaged.
Low-pressure bypass check ball
seat is oversized.
A particle of dirt or some other
foreign object is holding the low-
pressure relief valve open.
Low-pressure relief valve is set too
low.
Low-pressure bypass check ball
seat is damaged.
Low-pressure bypass check seat is
oversized.
The pilot piston does not advance
freely
Valve seat is damaged.
15
975 Hydraulic Power Pump
Probable Remedy
Disassemble, clean and inspect
spring (70) and 9/32" ball (71).
Replace parts as necessary.
See Hydraulic Schematic (4).
If set too low: The pump cannot
shift to the high-pressure stage. See
Pressure Adjustment for the Low-
Pressure Bypass Check, Figure A5 in
the Repairs section of this manual.
If set to high: The pump cannot
restart under pressure. See Pressure
Adjustment for the Low-Pressure
Bypass Check, Figure A5 in the
Repairs section of this manual.
See Ball Seat Refinishing, Figure B2,
B3 and B4 in the Repairs section of
this manual.
Replace the pump block (84).
Disassemble, clean and inspect
the valve piston (48), spring (47),
ball (46), spring (45) and stem (44).
Replace parts as necessary.
See Low-Pressure Relief Setting,
Figure A4 in the Repairs section of
this manual.
See Ball Seat Refinishing in the
Repairs section of this manual.
Figures B2, B3, and B4.
Replace the pump block (84).
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.
See Hydraulic Schematic (3, 7).
4455 Boeing Dr. • Rockford, IL 61109-2988 USA • 815-397-7070