30 Testing and adjusting SEN02458-01
PC138US, USLC-8
31
Testing and adjusting oil pressure
in pump PC control circuit 1
a Testing and adjusting tools for oil pressure in
pump PC control circuit
k Stop the machine on a level ground and
lower the work equipment to the ground.
Then, release the residual pressure from
the hydraulic circuit. For details, see
"Releasing residual pressure from hydrau-
lic circuit".
Testing
a Before testing the oil pressure in the PC con-
trol circuit, check that the oil pressure in the
work equipment, swing, and travel circuits and
the basic pressure of the control circuit are nor-
mal.
a Test the oil pressure in the pump PC control
circuit under the following condition.
q Hydraulic oil temperature: Within operating
range
1. Testing PC valve output pressure (servo
piston inlet pressure)
a Test the PC valve output pressure (servo
piston inlet pressure) and pump discharge
pressure simultaneously and compare
them.
1) Open the side cover of the pump room
and remove oil pressure pickup plugs (1)
and (2).
q (1): Pump discharge pressure pickup
plug
q (2): PC valve output pressure pickup
plug
2) Install nipple L2 and connect it to oil pres-
sure gauge [1] of hydraulic tester L1.
a Install nipple L2 to the inspection part
of plug (2) and connect it to oil pres-
sure gauge [1] by hose [2] of hydrau-
lic tester L1.
a Use the oil pressure gauges of 58.8
MPa {600 kg/cm
2
}.
3) Start the engine and move the arm cylin-
der to the IN stroke end.
4) Set the working mode in the power mode
(P).
Symbol Part No. Part name
L
1
799-101-5002 Hydraulic tester
790-261-1204 Digital hydraulic tester
2
799-101-5220 Nipple (10 × 1.25 mm)
07002-11023 O-ring
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