H-8 Bucket Speed Or Power Is Low - Komatsu PC88MR-10 Shop Manual

40 Troubleshooting
Troubleshooting of hydraulic and mechanical system (H-
mode)

H-8 Bucket speed or power is low

Bucket speed or power is low.
Failure
Perform all troubleshooting with working mode set in power (P) mode.
Related
Pump pressure can be checked with monitoring function. (monitoring code: 01100)
information
No. Cause
Malfunction of R.H.
PPC valve (bucket
1
circuit)
Malfunction of pump
2 merge-divider solenoid
valve
Malfunction of merge-
3
divider main spool
Malfunction of bucket
4
control valve (spool)
Malfunction of bucket
control valve (pressure
5
compensation valve)
(bucket CURL side)
40-476
(PC88MR-A8D-400-A-Z0-A)
Procedure, measuring location, criteria, and remarks
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
PPC valve output
pressure
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Work equipment control lever is in
Output pressure of
solenoid valve
a Release remaining pressure from hydraulic tank and piping, and then
perform troubleshooting with engine stopped.
Check for stuck or seized main spool in merge-divider valve body.
(Spool must move smoothly and must not be caught.)
Remove main spool from valve body and check it for defects and dirt.
Take care not to let foreign matter enter valve when re-installing spool.
a Release remaining pressure from hydraulic tank and piping, and then
perform troubleshooting with engine stopped.
Check for stuck or seized bucket spool in control valve body.
(Spool must move smoothly and must not be caught.)
Remove bucket spool from valve body and check it for defects and dirt.
Take care not to let foreign matter enter valve when re-installing spool.
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Bucket relief
pressure
a Check hydraulic drift of bucket cylinder with engine stopped.
Hydraulic oil temperature: Within
Hydraulic drift
cylinder fully extended, boom top
a Check whether bucket cylinder moves slowly when performing hydraulic
relief of other work equipment. (If bucket cylinder moves, it is abnormal.)
a If any failure is found in either of above check items, interchange pressure
compensation valves on bucket CURL and DUMP sides, and check
whether failure symptom changes.
(Each area ratio is different, so be sure to restore it after checking the
symptom.)
R.H. work
equipment NEUTRAL
control lever
R.H. work
equipment Arm IN or OUT
control lever
neutral
Bucket CURL and Arm IN
hydraulic relief
Bucket CURL relief
operating range,
bucket with rated load, arm
cylinder fully retracted, bucket
face horizontal
0 MPa {0 kg/cm 2 }
2.65 MPa {27 kg/
cm 2 } Min
0 MPa
{0 kg/cm 2 }
3.14 ± 0.5 MPa
{32 ± 5 kg/cm 2 }
26.5 ± 1.5 MPa
{270 ± 15 kg/cm 2 }
If visible hydraulic
drift is observed, it is
abnormal.
PC88MR-10