H-6 Boom Speed Or Power Is Low - Komatsu PC88MR-10 Shop Manual

H-6 Boom speed or power is low

Boom 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 (boom
1
circuit)
Malfunction of merge-
2
divider solenoid valve
Malfunction of merge-
3
divider main spool
Malfunction of merge-
4
divider LS spool
Malfunction of boom
5
control valve (spool)
Malfunction of boom
control valve (pressure
6
compensation valve)
(boom RAISE side)
PC88MR-10
Troubleshooting of hydraulic and mechanical system (H-
(PC88MR-A8B-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 LS spool in merge-divider valve body.
(Spool must move smoothly and must not be caught.)
Remove LS 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 boom spool in control valve body.
(Spool must move smoothly and must not be caught.)
Remove boom 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.
Boom relief pressure
a Check hydraulic drift of boom cylinder with engine stopped.
Hydraulic oil temperature within
operating range, bucket with rated
Hydraulic drift
a Check whether boom cylinder moves slowly when performing hydraulic
relief of other work equipment. (If boom cylinder moves, it is abnormal.)
a If any failure is found in either of above check items, interchange pressure
compensation valves on RAISE and LOWER sides, and check whether
failure symptom changes.
(Pressure compensation valves have different area ratio, so be sure to
return them to their original positions after test.)
R.H. work
equipment NEUTRAL
control lever
R.H. work
Boom RAISE or
equipment
LOWER
control lever
neutral
Bucket CURL and Arm IN
hydraulic relief
Boom RAISE hydraulic relief
load, boom horizontal, arm
cylinder fully retracted
40 Troubleshooting
mode)
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.
40-471