7. HYDRAULIC SYSTEM
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7.2.2 TRIAL RUN
Trial runs should be performed to run in an assembled pump and to ensure that it delivers the
specied performance. Trial runs are preferably carried on a special test stand, but may be carried out
with the pump on the machine using the following manner:
(If the pump were disassembled because of a seized pump or an abnormally worn internal component,
be sure to change the hydraulic oil and replace the lters with new ones before trying to make a trial
run.)
(a) Install the pump on the truck. Install a pressure gauge on the oil pressure check port of the control
valve.
(b) Loosen the relief valve adjustment screw and operate the pump at 500 to 1000 rpm for about 10
minutes. Make sure the pressure is less than 0.98 MPa {10 kgf/cm
2
} [142 psi].
(c) Increase the pump speed to 1500 to 2000 rpm and let the pump operate for about 10 minutes.
(d) Keeping the pump speed at 1500 to 2000 rpm, increase the pressure by 2 - 3 MPa {20 to 30 kgf/
cm
2
} [284 to 427 psi] up to 17.2 MPa {175 kgf/cm
2
} [2489 psi], letting the pump operate at each
pressure for about 5 minutes. Operate each circuit for 5 minutes and replace the return lter with a
new one.
While increasing the pressure, check the oil temperature and pump surface temperature. Check also
for operating noise. If the oil temperature or pump surface temperature rises excessively, reduce the
load and drop the temperature before continuing the test.
(e) After the test is over, set the oil pressure for 17.2 MPa {175 kgf/cm
2
} [2489 psi], perform a
discharge test. The pump discharge is checked by observing the lift speed.
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