H-12 The Lift Arm Does Not Rise Or Lower - Komatsu WA250-6 Shop Manual

SEN03849-00

H-12 The lift arm does not rise or lower

Ask the operator about the following:
Has the lift arm come not to work suddenly?
q
o
Seizure or breakage of each equipment
Did any abnormal noise occur at the time
(And where)?
Was there the phenomenon that the lift arm
q
worked slowly?
o Wear of parts or deformation of spring
Inspection before diagnosis
Is the oil level in the hydraulic tank appropriate?
q
Is the stroke of the lift arm control lever appro-
q
priate?
Is the engine speed appropriate?
q
No.
Diagnosis
The bucket cannot operate and the lift arm cannot
1
rise
The bucket operates but the lift arm cannot rise
2
The lift arm can rise without load but cannot rise
3
when loaded
4 The hydraulic pump causes an abnormal noise
5 Large hydraulic drift of lift arm cylinder
When the engine is at full throttle, the steering opera-
6
tion is heavy and slow
18
40-500
500 Troubleshooting of hydraulic and mechanical system (H-mode)
Tank to Pump
a b c d
C E E E
Remedy
E X X X
Q Q Q Q
Q Q Q
Q Q Q Q
Q Q
H-12 The lift arm does not rise or lower
Cause
Work
Priority HST PPC
equip-
valve pump valve
ment valve
e f g h
E E E
X X X X
Q Q Q
Q
Q
WA250, 250PZ-6
1
Cylinder
i j
X X
Q
Q
Q Q