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GENERAL
The tests in this section are provided as a means of
isolating a problem in the hydraulic system.
This section consists of two test methods. The first;
Relief Valve Tests, using pressure gauges only. Using
this method results in some test conclusions not being
final. Second; a Flow Test, an in-line hydraulic
flow/pressure instrument is used (see Figure 8J-1).
This method is more complete and will result in a final
conclusion of the failure.
Make sure the truck is secured and cannot roll.
There are two hydraulic systems used on these vehi-
cles. The first (standard system) consists of a single
section pump with a single selector valve. The second
is an optional High/Low System consisting of a 2 sec-
tion pump and two selector valves. Units with the
hydraulic PTO accessory also have a hydraulic motor.
Refer to he appropriate test procedures.
SECTION 8J. INSTRUMENT TEST
GPM
15
3
100
0
w
WEBSTER INSTRUMENTS
OFF RESET
TEST
TEMP
TACH
HI
FLOW
LO
9 VOLT BATTERY
Figure 8J-1. In-Line Tester
It is important to follow the instructions accurately and
completely. Make sure to plug lines and cap ports when
so instructed. Also, read and follow the Preliminary
Checks before proceeding with the instrument tests.
All of the tests in this section are shown using an
in-line tester shown in Figure 8J-1. When using
tester with variable gpm settings, make sure
tester is set for the proper flow range to avoid
damage to the test instrument. It is recommend-
ed that you record all readings obtained during
these tests. It is important that you accurately
run all tests at the same engine RPM and oil at
operating temperature.
200
300
400
20
30
10
40
0
8J-1
HYDRAULICS
IMPORTANT
8J
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