TM 10-4320-307-24
4-11
INJECTOR REPAIR (CONT).
b.
Check closely for metal seizure. This is the only true indication of scuffing or scoring.
c.
Bright spots or surface disruption at top of plunger machined area, on the opposite side at the bottom of
plunger, or at mid-point, usually are normal results of rocker lever thrust action. Unless metal is displaced or
wear is measurable at these points, the plunger can be reused. If barrel and plunger do not pass a leakage
test a new barrel and plunger assembly must be installed.
d.
Narrow streaks running the length of the plunger usually are the result of varying thicknesses of penetrant
treatment used to prevent rusting. The plunger may be reused unless surface disruption in metal is evident.
e.
Carbon deposits on the small diameter near tip of plunger may be caused by injector timing being set too
slow.
NOTE
This condition, if present, will have been observed and noted before cleaning.
7.
Inspect injector barrel as follows:
a. Inspect injector barrel plunger bore for scoring or corrosion. If injector will pass leakage test, the barrel is
usable. If leakage is too high, barrel and plunger must be replaced.
b.
Use a strong magnifying glass to check for burrs, carbon, and distorted radii in the orifice. When metering
orifice is damaged, the injector will not function properly. Do not attempt cleaning with wires, plug gauges,
etc. Use solvent cleaners.
c.
Check fuel passage plugs for looseness and the barrel for cracks.
d.
Check injector barrel surfaces for mutilation.
8.
Inspect check ball and barrel check ball seat as follows:
a.
Replace check ball if worn or damaged.
b.
Inspect check ball seat for damage.
c.
If damage is found, the check ball seat can be improved by lapping a ball to the seat as follows:
(1) Weld check ball to end of a small rod.
(2) Use 600 grade paste lapping compound to lap the seat.
(3) Clean lapping compound out of barrel.
d.
Inspect depth of check ball seat.
(1) Install check ball in barrel.
(2) Using depth micrometer, check that depth of ball does not exceed 0.055 inch (1.40 mm). If it does,
barrel and plunger must be replaced.
e.
Perform leakage test to determine if check ball and check ball seat form an adequate seal. Replace barrel
and ball if leakage exceeds recommended limits.
4-83
