Komatsu Galeo PC138US-8, Shop Manual

Page: 361 / 946

30 Testing and adjusting SEN02458-01
PC138US, USLC-8
33
Adjusting
Adjusting pump PC valve
a
If the following phenomenon occurs and PC
valve (4) seems to be defective, adjust PC
valve (4) according to the following procedure.
q
As the working load increases, the engine
speed lowers remarkably.
q
The engine speed is normal but the work
equipment speed is low.
a
The width across flats of the PC valve locknut
is 13 mm and that of the adjustment screw
(inside width) is 4 mm.
Do not turn any other locknuts or adjustment
screws since they affects the hydraulic pump
performance.
1. Loosen locknut (5).
a
Before loosening the locknut, make
counter mark at the adjustment screw end
so that you can see the position of the
locknut before the adjustment (and you
can return the locknut to its original posi-
tion after turning it in reverse).
2. Turn adjustment screw (6) clockwise or coun-
terclockwise to adjust.
a
Turn the adjustment screw
q
Clockwise when the work equipment
speed is low (to increase pump
absorption torque) and
q
Counterclockwise when the engine
speed lowers (to decrease pump
absorption torque).
3. Tighten locknut (5).
3
Locknut: 27 – 34 Nm {2.8 – 3.5 kgm}
4. After finishing adjustment, check again that the
PC valve output pressure (servo piston inlet
pressure) is normal according to the above
described test procedure.