Maeda MC815C - Boom Extending;Retracting Order Is Disturbed; Crane Cannot be Operated Discretely; Either Boom No. 2 or 3 Fails to Retract; Hunting Occurs During Boom Retraction

T-423
H-12 [Boom derricking speed is slow or derricking is weak]
Content Boom derricking is slow or weak
Assumed cause
and action to be
taken
Cause Diagnostic method and action to be taken
1
Boom derricking valve
(spool) operation fault
Check for malfunction of the boom derricking operation valve
spool
2 Boom derricking cylinder fault
★ Stop engine to perform preparations and conduct diagnosis
at a high engine idling speed.
•
Boom derricking cylinder: during retracting relief
Cylinder leakage rate: 5 cc / 10 min
•
Check for malfunction of the boom derricking cylinder
counter-balanced valve
•
Check for malfunction / deformation in the boom derricking
cylinder
3 Swivel joint faults • Check for internal leakage due to swivel joint faults
H-13 [Boom extending/retracting order is disturbed]
Content Boom extending/retracting order is disturbed
Assumed cause
and action to be
taken
Cause Diagnostic method and action to be taken
1
Sequence valve operation
fault
Check for sequence valve malfunction
2
Mechanical check valve
operation fault
Check for mechanical check valve malfunction
H-14 [Hunting occurs during boom retraction]
Content Hunting occurs during boom retraction.
Assumed cause
and action to be
taken
Cause Diagnostic method and action to be taken
1
Counterbalancing valve
operation fault
Check for counter balanced valve malfunction
2
Grease run-out on boom
sliding surface
It is possible that the grease has run out on the boom sliding
surface, so apply grease
H-15 [Either boom No. 2 or 3 fails to retract]
Content Either boom No. 2 or 3 fails to retract
Assumed cause
and action to be
taken
Cause Diagnostic method and action to be taken
1
Mechanical check valve
operation fault
Check for mechanical check valve malfunction
2
Fault of mechanical check
valve push button
Check for faults with the mechanical check valve push button
H-16 [Crane cannot be operated discretely]
Content Crane cannot be operated discretely
Assumed cause
and action to be
taken
Cause Diagnostic method and action to be taken
1
Crane pilot solenoid
operation fault
• Check if there are operation faults with the crane pilot solenoid
(travelling / outrigger control valve)
2 Piston pump fault
Piston pump A3 port pressure measurement
Pilot pressure: 3.1 Mpa [32 kg/cm
2
]
Piston pump A1 / A2 port pressure measurement
At retracting relief: 20.6 Mpa [210 kg/cm
2
]