H-20 Machine Does Not Travel Straight - Komatsu PC88MR-10 Shop Manual

H-20 Machine does not travel straight

Machine does not travel straight.
Failure
Perform all troubleshooting with working mode set in power (P) mode.
If failure codes are displayed, perform troubleshooting for them first. (DW91KA, DW91KB)
Related
Travel PPC pressure can be checked with monitoring function. (monitoring code: 07102,
information
07103, 07104, 07105)
No. Cause
Malfunction of self-
1
pressure reducing valve
Malfunction of R.H.
2
travel PPC valve
Malfunction of L.H.
3
travel PPC valve
Malfunction of pump
4 merge-divider solenoid
valve
Defective adjustment of
5
LS valve
Malfunction of travel
6
junction valve (spool)
PC88MR-10
Troubleshooting of hydraulic and mechanical system (H-
Procedure, measuring location, criteria, and remarks
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Control circuit
source pressure
a Since relief valve of self-pressure reducing valve is not adjustable, replace
self-pressure reducing valve assembly if normal pressure is not obtained.
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
R.H. travel lever
R.H. travel PPC
valve output
pressure
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
L.H. travel lever
L.H. travel PPC
valve output
pressure
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Output pressure of
solenoid valve
a Be ready with engine stopped, then perform troubleshooting with engine at
high idle.
Oil pressure to be
measured
Pump discharge Almost same as LS valve output
pressure
LS valve output Almost same as pump discharge
pressure
a Release remaining pressure from hydraulic tank and piping, and then
perform troubleshooting with engine stopped.
Check for stuck or seized travel junction valve spool in merge-divider
valve body.
(Spool must move smoothly and must not be caught.)
Remove travel junction valve spool from valve body and check it for
defects and dirt.
(PC88MR-FTF-400-A-Z0-A)
All levers in NEUTRAL
NEUTRAL
FORWARD or
REVERSE
Difference in output pressures
between L.H. and R.H. PPC
valves
NEUTRAL
FORWARD or
REVERSE
Difference in output pressures
between L.H. and R.H. PPC
valves
All levers in NEUTRAL
Travel lever is operated
independently.
Lever position and oil pressure ratio
All levers in NEUTRAL
pressure
pressure
40 Troubleshooting
mode)
3.2 ± 0.5 MPa
{33 ± 5 kg/cm 2 }
0 MPa {0 kg/cm 2 }
Min. 2.65 MPa
{Min. 27 kg/cm }
2
Max. 0.4 MPa
{Max. 4 kg/cm 2 }
0 MPa {0 kg/cm 2 }
Min. 2.65 MPa
{Min. 27 kg/cm 2 }
Max. 0.4 MPa
{Max. 4 kg/cm 2 }
0 MPa {0 kg/cm 2 }
3.14 ± 0.5MPa
{32 ± 5 kg/cm 2 }
L.H. track: Running
idle off ground in Hi
speed setting
Lever moved
halfway
1
Approx. 0.6 (Approx.
3/5)
40-493