TM 5-3810-300-24&P-3
2.0
SHOP NOTES - TROUBLE SHOOTING - SPECIFICATIONS
SERVICE TOOLS
SHOP NOTES
INJECTOR COMPARATOR AND CALIBRATOR READINGS
bottom, a variation of I or 2 points will result. Refer to
Fig. 1.
2. Air In Lines: This can be caused by starting a test
before the air is purged from the injector and lines, or
from an air leak on the vacuum side of the pump.
3. Counter Improperly Set: The counter should be
set to divert the injector output at 1,000 strokes.
This should not be confused with counter overrun that
will vary from 2 to 6 digits, depending upon internal
friction. The fuel diversion is accomplished electrically
and will occur at 1,000 strokes (if properly set) although
the counter may overrun several digits.
4. Test Oil: A special test oil is supplied with the
comparator and the calibrator and should always be
used. If regular diesel fuel oil (or any other liquid) is
used, variations are usually noted because of the effect
of the oil on the solenoid valve and other parts.
The fuel oil introduced into the test oil when the fuel
injector is placed in the comparator or calibrator for a
Fig. 1 - Checking Fuel Output
calibration check contaminates the test oil. Therefore, it
is important that the test oil and test oil filter be changed
Several factors affect the injector comparator or
every six months, or sooner if required.
calibrator output readings. The four major items are:
In addition, other malfunctions such as a slipping drive
1. Operator Errors: If the column of liquid in the vial
belt, low level of test oil, a clogged filter, a defective
is read at the top of the meniscus instead of at the
pump or leaking line connections could cause bad
readings. A frequent check should be made for any of
these tell-tale conditions.
CHECKING INJECTOR TESTER J 9787
The injector tester J 9787 should be checked monthly to
connector clamp. Operate the pump handle until all of
be sure that it is operating properly. The following check
the air is out of the test block, then clamp the fuel outlet
can be made very quickly using test block J 9787-49.
connector onto the test block. Break the connection at
the gage and operate the pump handle until all of the air
Fill the supply tank in the injector tester with clean
bubbles in the- fuel system disappear. Tighten the
injector test oil J 8130. Open the valve in the fuel supply
connection at the gage. Operate the pump handle to
line. Place the test block on the injector locating plate
pressurize the tester fuel system to 2400-2500 psi.
and secure the block in place with the fuel inlet
Close the valve on the fuel supply line. After a slight
initial drop, the pressure should remain steady. This
indicates that the injector tester is operating properly.
Open the fuel valve and remove the test block.
If there is a leak in the tester fuel system, it will be
indicated by a drop in pressure. The leak must be
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