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5-29
5
BOOM
TROUBLESHOOTING
When the boom control lever is pulled slowly, the boom drops at first
1
Check the load check
valve of the control valve
Faulty
Repair or replace the housing
block
Normal
2
Check for leakage inside
the boom cylinder
Faulty
Repair or replace the boom
cylinder
1. Check the load check valve of the control valve
a. Disconnect the hose connecting the control valve
and the boom cylinder from the control valve.
b. Connect the hose just disconnected to the boom or
bucket block.
c. Try to operate the boom cylinder.
If operation is normal, the load check valve is faulty.
Before performing steps “a” through “c” above, set
the machine as follows.
• Fully extend the bucket cylinder, completely re-
tract the arm cylinder and lower the bucket to the
ground.
When the spool first starts to pull, the oil’s pressure
and the flow rate are small, so if the load check valve
is faulty, it causes a load to act on the boom cyl-
inder, which causes the oil to flow backward for a
time. This is what causes the boom to drop at first.
2. Check for leak inside the boom cylinder
If the oil is leaking from the head side (A) to the rod
side (B) due to a faulty arm cylinder piston or tube, the
lift arm first drops because of the low oil pressure and
small flow rate when the spool begins to pull. The driv-
ing force of the cylinder is also insufficient. In this case,
the spontaneous drop of the boom becomes large.
• Check the cylinder
“5-27 and 28”
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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...