TM 5-4310-379-14
5-11. Fuel Injectors (Cont).
a.
Test. (figure 5-5)
(1) Using injector fixture and rack freeness tester check for freeness of rack. If the rack (1) does not fall freely
it may be necessary to loosen injector nut (2), turn spray tip (3), and retighten injector nut to 75-85Ib-ft
(102-115 Nm). If rack still binds, repair fuel injector.
(2) Depress follower (4), raise spring (5) above stop pin (6) and remove pin (6) and allow spring (5) to raise
gradually.
(3)
Remove follower (4), spring (5), and plunger (7).
(4)
Inspect plunger (7) and repair fuel injector if plunger is chipped, scored, or otherwise damaged.
(5)
Place stop pin (6) in injector body (8).
(6)
Install spring (5) on injector body (8) so that spring (5) rests on narrow flange of stop pin (6).
(7)
Aline slot in follower (4) with stop pin (6).
(8)
Aline flat side of plunger (7) with slot in the follower (4).
(9)
Install plunger (7) in injector body (8).
(10)
Press on follower (4) while pressing on stop pin (6). When follower (4) is in place, the spring (5) will hold
stop pin (6).
(11)
Install fuel injector in fuel injector tester.
(12)
Test spray pattern and valve opening operations. Observe the spray pattern to see that all orifices are
open and test fluid is dispersed evenly. The test oil should be finely atomized with no drops of test oil
forming on the end of the tip. The acceptable pressure readings are 127-146 psi (876-1007 kPa).
(13) Perform high pressure test on injector. Pump up pressure to 1600-2000 psi (11,024-13,780 kPa). Check
for leakage at injector filter caps (9), body plugs (10), and nut seal ring (11). Repair a fuel injector that
leaks.
(14) Perform pressure holding test. Pressurize fuel injector to 700 psi (4,823 kPa). Time the pressure drop
from 450-down to 250 psi (3, 100 down to 1, 723 kPa). If the pressure drop occurs in less than 15
seconds, leakage is excessive. Repair a fuel injector that has excessive leakage.
NOTE
Needle valve tip test and spray tip leakage test can also be performed using injector tester and
auxiliary tester.
5-18
