DETROIT DIESEL 53
SHOP NOTES-TROUBLE SHOOTING-SPECIFICATIONS-SERVICE TOOLS
CHECKING INJECTOR TESTER J 9787
Occasionally dirt will get into the pump check valve in
The injector tester J 9787 should be checked monthly
the tester, resulting in internal pump valve leakage
to be sure that it is operating properly. The following
and the inability to build up pressure in the tester fuel
check can be made very quickly using test block
system. Pump valve leakage must be corrected before
an injector can be properly tested.
Fill the supply tank in the injector tester with clean
injector test oil J 8130. Open the valve in the fuel
When the above occurs, loosen the fuel inlet connector
supply line. Place the test block on the injector locating
clamp and operate the tester pump handle in an
plate and secure the block in place with the fuel inlet
attempt to purge the dirt from the pump check valve.
connector clamp. Operate the pump handle until all of
A few quick strokes of the pump handle will usually
the air is out of the test block; then clamp the fuel
correct a dirt condition. Otherwise. the pump check
outlet connector onto the test block. Break the
valve must be removed, lapped and cleaned. or
connection at the gage and operate the pump handle
until all of the air bubbles in the fuel system
If an injector tester supply or gage line is damaged or
disappear. Tighten the connection at the gage. Operate
broken, install a new replacement line (available from
the pump handle to pressurize the tester fuel system to
the tester manufacturer). Do not shorten the old lines
2400-2500 psi. Close the valve on the fuel supply line.
or the volume of test oil will be altered sufficiently to
After a slight initial drop in pressure. the pressure
give an inaccurate valve holding pressure test.
should remain steady. This indicates that the injector
tester is operating properly. Open the fuel valve and
If it is suspected that the lines have been altered, i.e.
remove the test block.
by shortening or replacing with a longer line, check
the accuracy of the tester with a master injector on
If there is a leak in the tester fuel system, it will be
which the pressure holding time is known. If the
indicated by a drop in pressure. The leak must be
located, corrected and the tester rechecked before
pressure holding time does not agree with that
checking an injector.
recorded for the master injector, replace the lines.
REFINISH LAPPING BLOCKS
As the continued use of the lapping blocks will cause
worn or low spots to develop in their lapping surfaces,
they should be refinished from time to time.
It is a good practice, where considerable lapping work
is done. to devote some time each day to refinishing
the blocks. The quality of the finished work depends to
a great degree on the condition of the lapping surfaces
of the 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. 1. Alternate the blocks from
time to time. For example. assuming the blocks are
numbered 1, 2 and 3, work 1 and 2 together, then 1
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
Fig. 1 - Refinishing Lapping Blocks
and held under a strong light. The blocks are
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