TM 5-3895-346-14
FUEL INJECTOR
ENGINE OVERHAUL
If inspection does not reveal any external damage, perform a series of tests to determine the condition of the
injector to avoid unnecessary overhauling. Tests must be performed using injector test oil J 26400.
An injector that passes all of the tests outlined below may be considered to be satisfactory for service without
disassembly, except for the visual check of the plunger.
However, an injector that fails to pass one or more of the tests is unsatisfactory. Perform all of the tests before
disassembling an injector to correct any one condition.
Identify each injector and record the pressure drop and fuel output as indicated by the following tests.
Injector Control Rack and Plunger Movement Test
Place the injector in the injector fixture and rack freeness tester J 22396. Refer to Fig. 8 and place the handle
on top of the injector follower.
If necessary, adjust the contact screw in the handle to ensure the contact screw is at the center of the follower
when the follower spring is compressed.
Figure 8. Checking Rack and Plunger for Free Movement with J 22396
With the injector control rack held in the no-fuel position, push the handle down and depress the follower to the
bottom of its stroke. Then very slowly release the pressure on the handle while moving the control rack up and
down as shown in Fig. 8 until the follower reaches the top of its travel. If the rack does not fall freely, loosen
the injector nut, turn the tip, then retighten the nut. Loosen and retighten the nut a couple of times if necessary.
Generally this will free the rack. Then, if the rack isn't free, change the injector nut. In some cases it may be
necessary to disassemble the injector to eliminate the cause of the misaligned parts.
Visual Inspection of Plunger
An injector which passes all of the previous tests should have the plunger checked visually, 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
lower portion of the upper helix that, if chipped, will not be indicated in any of the tests.
Remove the plunger from the injector as follows:
1. Support the injector, right side up, in holding fixture J 22396.
2. Compress the follower spring. Then raise the spring above the stop pin with a screwdriver and withdraw the
pin (Fig. 9). Allow the spring to rise gradually.
3. Remove the injector from the holding fixture. Turn the injector upside down, to prevent the entry of dirt, and
catch the spring and plunger as they drop out.
4. Inspect the plunger. If the plunger is chipped (Fig. 10), replace the plunger and bushing assembly.
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