TROUBLESHOOTING
BOOM
2
5
BOOM 5G0AX001
2. Check the pilot valve.
Disconnect the hose connecting the pilot valve and
the control valve (boom block) from the control valve.
Fit the pressure gauge to the hose just disconnected.
• Operate the lever (boom) and measure the pres-
sure.
• If the pressure is between 0 and 3.4 MPa (0 to 493
PSI) depending on the lever angle, the pilot valve
is normal.
3. Check the spool operation.
Disconnect the hose connecting the control valve
(boom block) and the boom cylinder from the cylin-
der. Fit the pressure gauge to the discharge port on
the control valve.
• Operate the lever (boom) and measure the pres-
sure.
Supply pressure: 21.0 MPa (3045 PSI)
4. Test by replacing the port relief valve.
Replace the port relief valve in question with a normal
port relief valve. If the boom cylinder operates with
the replacement valve, the port relief valve used on
the boom side is faulty.
Make sure to return the port relief valve to its regular
position after the above inspection.
5. Check the boom cylinder.
a. Disconnect the hose connecting the control valve
and the boom cylinder from the control valve side.
b. Connect the hose just disconnected to the arm or
bucket block.
c. Try to operate the boom cylinder. If the cylinder
fails to operate, the cylinder is faulty.
Before performing steps “a” through “c” above, fully
extend the bucket cylinder, completely retract the
arm cylinder and lower the bucket to the ground.
5G0AI01Z
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