V-9
TROUBLESHOOTINGOVERALL MACHINE
LIFT ARMS AND BUCKET FAIL TO MOVE/SPEED OF OPERATION POOR.
Inspect the pilot valve.
3
Inspect the main relief
valve.
2
Inspect hydraulic pump
P3.
1
Repair or replace hydraulic
pump P3.
Repair or replace the main
relief valve.
Repair or replace the pilot
valve.
Normal
Faulty
Faulty
1. Inspect hydraulic pump P3.
“V-5”
2. Inspect the main relief valve.
Measure the relief pressure of the main relief
valve.
• The main relief valve is working properly if
the pressure is normal.
“II. Specifications, Standards for Judging
Performance”
If the main relief valve·s set pressure is too low,
adjust it by tightening the valve set screw gradu
-
ally.
• If the pressure does not rise even after the
screw has been turned onequarter of a full
rotation, the relief valve may be judged to be
at fault.
Points to be careful about during assembly
and disassembly:
• Always be sure to remove box nut (2), mea
-
sure the size of the set screw (1) in position A,
and record the measured value.
• Check to see if any foreign matter has worked
its way into the valve or whether there are any
scratches or other damage on the surface of
the poppet sheet.
• When reassembling, see that the length A of
the set screw is somewhat greater than that at
the time of disassembly, screwing it in slowly
to adjust the set pressure.
3. Inspect the pilot valve.
“IV. Hydraulic Units, Pilot Valve”
Faulty
Normal
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