A drop or two of fuel at the spray tip is only
an indication of the fuel trapped in the spray tip
at the beginning of the test. It is not detrimental
as long as the pressure drop specified is not less
than 40 seconds.
HIGH-PRESSURE TEST. This testis performed
to discover arty fuel leaks at the injector filter cap
gaskets, body plugs, and nut seal ring which did not
appear during the valve holding pressure test. The
high-pressure test also indicates whether the injector
plunger and bushing clearance are satisfactory. To
perform the test, place the injector rack in the
FULL-FUEL position. Operate the pump handle (fig.
5-30) to build up and maintain a pressure of 1,600 to
2,000 psi. Then inspect the injector filter cap gaskets,
body plugs, and injector nut seal ring for leaks.
Next, you should use the adjusting screw in the
injector tester handle to depress the injector plunger just
far enough to close both ports in the injector bushing.
Both ports are closed if the injector spray decreases and
the pressure rises. Now, you can determine the condition
of the plunger and bushing. If there is excessive
clearance between the plunger and bushing, it means
that pressure will not rise beyond the normal
valve-opening pressure. Next, you should replace the
SPRAY PATTERN TEST. This test is performed
after you have completed the valve holding pressure
test. After placing the injector in the tester, open the fuel
shutoff valve; then place the injector rack in the
FULL-FUEL position. Operate the injector several
times in succession by pumping the tester handle (fig.
5-31) at approximately 40 strokes per minute. Observe
the spray pattern to see whether all of the spray tip
orifices are open and injecting evenly. The beginning
and ending of injection should be sharp, and the fuel
injected should be finely atomized. If all the spray tip
orifices are not open and injecting evenly, clean the
orifices in the spray tip during injector overhaul.
To prevent damage to the pressure gauge,
do not exceed 250 psi during this test.
You should visually inspect the injector plunger
even if the injector passes all of the previous tests. The
plunger is visually checked under a magnifying glass for
excessive wear or a possible chip on the bottom helix.
There is a small area on the bottom helix and the lower
portion of the upper helix, that, if chipped, will not be
indicated in any of the tests.
FUEL OUTPUT TEST. This test is performed to
check injector fuel output. To test the injector, place it
plunger and bushing.
Figure 5-30.-Injector high-pressure test.
Figure 5-31.-Spray pattern test.