DETROIT DIESEL 53
Fuel Injector 2.1.1
or scratches. Also check the surface which contacts the
injector bushing for scratches, scuff marks or other
damage. If necessary, lap this surface. A faulty sealing
surface at this point will result in high fuel consumption
and contamination of the lubricating oil. Replace any
loose injector body plugs or a loose dowel pin. Install
the proper number tag on a service replacement injector
body.
Inspect the injector plunger and bushing for scoring,
erosion, chipping or wear. Check for sharp edges on
that portion of the plunger which rides in the gear.
Remove any sharp edges with a 500 grit stone. Wash
the plunger after stoning it. Injector Bushing Inspectalite
J 21471 can be used to check the port holes in the inner
diameter of the bushing for cracks or chipping. Slip the
plunger into the bushing and check for free movement.
Replace the plunger and bushing as an assembly if any
of the above damage is noted, since they are mated
parts. Use new mated factory parts to assure the best
performance from the injector.
Injector plungers cannot be reworked to change the
output. Grinding will destroy the hardened case at the
helix and result in chipping and seizure or scoring of the
plunger.
Examine the spray tip seating surface of the injector nut
and spray tip for nicks, burrs, erosion or brinelling.
Fig. 37. - Injector Plunger, Follower and
Reseat the surface or replace the nut or tip if it is
Relative Location of Parts
severely damaged.
The injector valve spring plays an important part in
Part
Minimum
establishing the valve opening pressure of the injector
Name
Thickness
assembly. Replace a worn or broken spring.
Tip, Spray (Shoulder)
.199
Cape, Check Valve
.165-.163
Inspect the sealing surfaces of the injector parts
Volve, Check
.022
indicated by arrows in Fig. 31. Examine the sealing
Cage, Valve Spring
.602
surfaces with a magnifying glass as shown in Fig. 32.
for even the slightest imperfections will prevent the
MINIMUM THICKNESS (Used Parts)
injector from operating properly. Check for burrs, nicks,
erosion, cracks, chipping and excessive wear. Also
stick 6 to 12 times, applying a light pressure with the
check for enlarged orifices in the spray tip. Replace
thumb and forefinger.
damaged or excessively worn parts.
Check the
CAUTION:
Be sure that no
minimum thickness of the lapped parts as noted in the
compound is accidentally placed on
chart.
the lapped surfaces located higher
up in the spray tip. The slightest
Examine the seating area of the needle valve for wear
lapping action on these surfaces can
or damage. Also examine the needle quill and its
alter the
contact point with the valve spring seat. Replace
damaged or excessively worn parts.
Examine the needle valve seat area in the spray tip for
foreign material. The smallest particle of such material
can prevent the needle valve from seating properly.
Polish the seat area with polishing stick J 22964. Coat
only the tapered end of the stick with polishing
compound J 23038 and insert it directly into the center
of the spray tip until it bottoms.
Rotate the
1972 General Motors Corp.
July, 1972
SEC. 2.1.1 Page 17
