Engine Speed Sharply Drops Or Engine Stalls - Komatsu Galeo PC138US-8 Shop Manual

40 Troubleshooting
H-2 Engine speed sharply drops or engine stalls
Trouble • Engine speed sharply drops or the engine stalls.
Related
• Conduct the troubleshooting in working mode P.
information
Defective adjustment or
1
operation of main relief valve
Defective adjustment or
2
Possible causes
operation of PC valve
and standard
value in normal
state
Defective adjustment or
3
operation of LS valve
Orifice or filter in servo
4
equipment clogged
5 Malfunction of servo piston
PC138US, USLC-8
Cause Standard value in normal state/Remarks on troubleshooting
a
Arm relieved in IN direction
If the oil pressure cannot be set normally by adjustment, the main
relief valve may be malfunction or may have an internal defect.
Check the main relief valve directly.
a
Pump discharge
PC valve output
If the oil pressure cannot be set normally by adjustment, the PC
valve may be malfunction or may have an internal defect. Check
the PC valve directly.
Pump discharge
LS valve output
If the oil pressure cannot be set normally by adjustment, the LS
valve may be malfunction or may have an internal defect. Check
the LS valve directly.
The orifice or filter in the pump servo equipment is suspected of
clogging. Check the equipment itself.
The servo piston may have malfunction. Check it directly.
Keep the engine stopped for the preparations, and keep it
running at high idle during the troubleshooting.
Control lever
Keep the engine stopped for the preparations, and keep it
running at high idle during the troubleshooting.
Measured oil Measurement
pressure conditions
Swing lock: ON
pressure
Arm: Relieved in IN
direction
pressure
Measured oil
All levers in
pressure
NEUTRAL
pressure
Almost same
pressure
pressure
SEN02468-01
Main relief pressure
+2.0
34.8 MPa
–1.0
+20
{355 kg/cm }
2
–10
Oil pressure ratio
1
Approx. 0.6
(Approx. 3/5)
Oil pressure ratio
Bucket curled
(Lever at stroke end)
1
Approx. 0.6
(Approx. 3/5)
1
7