5-31
5
ARM
TROUBLESHOOTING
ARM
Arm cylinder does not move
1
Check the operation of
actuators other than of
the arm cylinder
Normal
2 Check the pilot valve
Faulty
Repair
or replace the pilot
valve
Normal
3
Check
the spool opera-
tion
Faulty
Repair
or replace the housing
block
Normal
4
T
est by replacing the port
relief valve
Problem solved
The port relief valve is
faulty
Repair
or replace the port re-
lief valve.
No change
5 Check the arm cylinder
.
Faulty
Repair
or inspect the arm cyl-
inder
1. Check the operation of actuators other than of the
arm cylinder
Determine if only the arm cylinder is faulty by checking
the operation of actuators for the devices listed in the
table on the right.
If it is faulty, check the main relief valve and the hydrau-
lic pump (main).
“5-5”
2. Check the pilot valve
Disconnect the hose connecting the pilot valve and the
control valve (arm block) from the control valve. Fit the
pressure gauge to the hose just disconnected.
• Operate the lever (arm) and measure the pressure.
• If the pressure is between 0 and 3.4 MPa depending
on the lever angle, the pilot valve is normal.
Lever to operate
Device to check
Relief valve Pump
Left travel
TB228,235: R1 TB228,235: P1
TB250: R2 TB250: P2
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