If an injector tester supply or gage line is damaged or
Occasionally dirt will get into the pump check valve in
broken, install a new replacement line (available from
the tester, resulting in internal pump valve leakage and
the tester manufacturer). Do not shorten the old lines or
the inability to build up pressure in the tester fuel
the volume of test oil will be altered sufficiently to give
system. Pump valve leakage must be corrected before
an inaccurate valve holding pressure test.
an injector can be properly tested.
If it is suspected that the lines have been altered, i.e. by
When the above occurs, loosen the fuel inlet connector
shortening or replacing with a longer line, check the
clamp and operate the tester pump handle in an attempt
accuracy of the tester with a master injector on which
to purge the dirt from the pump check valve. A few
the pressure holding time is known. If the pressure
quick strokes of the pump handle will usually correct a
holding time does not agree with that recorded for the
dirt condition. Otherwise, the pump check valve must
be removed, lapped and cleaned or replaced (J 9787).
The pump check valve must be replaced on tester J
REFINISH LAPPING BLOCKS
To refinish the blocks, spread some 600 grit lapping
powder of good quality on one of the blocks. Place
another block on top of this one and work the blocks
together as shown in Fig. 2. Alternate the blocks from
time to time. For example, assuming the blocks are
numbered 1, 2 and 3, work I and 2 together, then I and
3, and finish by working 2 and 3 together. Continue this
procedure until all of the blocks are perfectly flat and
free of imperfections.
Imperfections are evident when the blocks are clean and
held under a strong light. The blocks are satisfactory
Fig. 2 Refinishing Lapping Blocks
when the entire surface is a solid dark gray. Bright or
exceptionally dark spots indicate defects and additional
lapping is required.
As the continued use of the lapping blocks will cause
worn or low spots to develop in their lapping surfaces,
After the surfaces have been finished, remove the
they should be refinished from time to time.
powder by rinsing the lapping blocks in trichloroethylene
and scrubbing with a bristle brush.
It is good practice, where considerable lapping work is
done, to devote some time each day to refinishing the
When not in use, protect the lapping blocks against
blocks. The quality of the finished work depends to a
damage and dust by storing them in a close fitting
great degree on the condition of the lapping surfaces of
MASTER INJECTOR CALIBRATING KIT
Use Master Injector Calibrating Kit J 26298 to determine
Injector testing can be carried out now without any
the accuracy of the injector calibrator.
adjustment of figures. However, when testing new
injectors for output, any difference between the
With the test fluid temperature at 100 1 (38 1
calibrator and the masters should be used to compute
and each injector warm after several test cycles, run
the three injectors contained in the kit. Several readings
from the masters is noted, consult the calibrator
should be taken with each injector to check for accuracy
manufacturer for possible causes.
and repeatability. If the output readings are within 2% of
the values assigned to the calibrated masters, the
The calibrated masters should only be used to qualify
calibrator can be considered accurate.