SHOP NOTES - TROUBLE SHOOTING -
SPECIFICATIONS - SERVICE TOOLS
INJECTOR CALIBRATOR READINGS
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
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
The fuel oil introduced into the test oil when the fuel
injector is placed in the calibrator for a calibration check
Fig. 1. Checking Fuel Output
contaminates the test oil. Therefore, it is important that
Several factors affect the injector calibrator output
the test oil and test oil filter be changed every six
readings. The four major items are: 1. Operator
months, or sooner if required.
Errors: If the column of liquid in the vial is read at the
top of the meniscus instead of at the bottom, a variation
In addition, other malfunctions such as a slipping drive
of I or 2 points will result. Refer to Fig. 1.
belt, low level of test oil, a clogged filter, a defective
pump or leaking line connections could cause bad
readings. A frequent check should be made for any of
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.
CHECKING INJECTOR TESTER J 9787 or J 23010
bubbles in the fuel system disappear. Tighten the
The injector tester (J 9787 or J 23010) should be
connection at the gage. Operate the pump handle to
checked monthly to be sure that it is operating properly.
pressurize the tester fuel system to 2400-2500 psi. (16
The following check can be made very quickly using test
536-17 225 kPa). Close the valve on the fuel supply
block J 9787-49.
line. After a slight initial drop, the pressure should
remain steady. This indicates that the injector tester is
Fill the supply tank in the injector tester with clean
operating properly. Open the fuel valve and remove the
injector test oil J 26400. Open the valve in the fuel
supply line. Place the test block on the injector locating
plate and secure the block in place with the fuel inlet
If there is a leak in the tester fuel system, it will be
connector clamp. Operate the pump handle until all of
indicated by a drop in pressure. The leak must be
the air is out of the test block, then clamp the fuel outlet
located, corrected and the tester rechecked before
connector onto the test block. Break the connection at
checking an injector.
the gage and operate the pump handle until all of the air