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5-25
5
BOOM
TROUBLESHOOTING
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 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 cylinder.
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
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.
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Summary of Contents for TB 250
Page 1: ......
Page 3: ...1 1 SAFETY 1 Safety alert symbol 1 2 Safety precautions 1 3 Cautions when working 1 9...
Page 36: ...2 24 2 TIGHTENING TORQUE SERVICE DATA...
Page 38: ...2 26 2 HYDRAULIC CIRCUIT DIAGRAM SERVICE DATA Equipped with options 2 2...
Page 39: ...2 27 2 HYDRAULIC CIRCUIT DIAGRAM SERVICE DATA Equipped with angle blade and blade oat 1 2...
Page 40: ...2 28 2 HYDRAULIC CIRCUIT DIAGRAM SERVICE DATA Equipped with angle blade and blade oat 2 2...
Page 41: ...2 29 2 HYDRAULIC CIRCUIT DIAGRAM SERVICE DATA Equipped with high ow option 1 2...
Page 42: ...2 30 2 HYDRAULIC CIRCUIT DIAGRAM SERVICE DATA Equipped with high ow option 2 2...
Page 49: ......
Page 59: ...2 46 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 60: ...2 47 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 61: ...2 48 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 62: ...2 49 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 63: ...2 50 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 64: ...2 51 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 65: ...2 52 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 66: ...2 53 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 67: ...2 54 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 68: ...2 55 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 69: ...2 56 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 70: ...2 57 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 71: ...2 58 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 72: ...2 59 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 73: ...2 60 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA NAME STANDARD NO...
Page 74: ...2 61 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 75: ...2 62 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 76: ...2 63 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 77: ...2 64 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 78: ...2 65 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 79: ...2 66 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 80: ...2 67 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 81: ...2 68 2 WIRE HARNESS WIRING DIAGRAM SERVICE DATA...
Page 92: ...3 11 3 CONTROL VALVE FUNCTION...
Page 108: ...4 3 4 SERVICE STANDARDS DISASSEMBLY AND ASSEMBLY Clearance for pin and bushing...
Page 352: ...ENGINE 6 Machine model Mounted engine TB250 4TNV88...