CHECKING INJECTOR TESTER J 23010 OR J 9787
The injector tester J 23010 or J 9787 shoul4 be checked monthly to be sure that it is operating properly. The
following check can be made very quickly using test block J 9787-49.
Fill the supply tank in the injector tester with clean 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
connector clamp. Operate the pump handle until all of the air is out of the test block, then clamp the fuel outlet
connector onto the test block. Break the connection at the gage and operate the pump handle until all of the air
bubbles in the fuel system disappear. Tighten the connection at the gage. Operate the pump handle to
pressurize the tester fuel system to 2400-2500 psi (16 536-17 225 kPa). 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 located,
corrected and the tester rechecked before checking an injector. Occasionally dirt will get into the pump check
valve in the tester, resulting in internal pump valve leakage and the inability to build up pressure in the tester
fuel system. Pump valve leakage must be corrected before an injector can be properly tested.
When the above occurs, loosen the fuel inlet connector clamp and operate the tester pump handle in an
attempt to purge the dirt from the pump check valve. A few quick strokes of the pump handle will usually
correct a dirt condition. Otherwise, the pump check valve must be removed, lapped and cleaned, or replaced
(J 9787). The pump check valve in J 23010 must be replaced.
If an injector tester supply or gage line is damaged or broken, install a new replacement line (available from the
tester manufacturer). Do not shorten the old lines or the volume of test oil will be altered sufficiently to give an
inaccurate valve holding pressure test.
If it is suspected that the lines have been altered, i.e. by shortening or replacing with a longer line, check the
accuracy of the tester with a master injector on which the pressure holding time is known. If the pressure
holding time does not agree with that 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 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
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.