DETROIT DIESEL 53
Fuel Injector 2.1.1
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. Re-seat the
surface or replace the nut or tip if it is severely damaged.
The injector valve spring plays an important part in establishing the valve opening pressure of the injector assembly.
Replace a worn or broken spring.
Inspect the sealing surfaces of the injector parts indicated by arrows in Fig. 31. Examine the sealing surfaces with a
magnifying glass as shown in Fig. 32 for even the slightest imperfections will prevent the injector from operating properly.
Check for burrs, nicks, erosion, cracks, chipping and excessive wear. Also check for enlarged orifices- in the spray tip.
Replace damaged or excessively worn parts. Check the minimum thickness of the lapped parts as noted in the chart.
Tip, Spray (shoulder
Cage, Check Valve
Cage, Valve Spring
MINIMUM THICKNESS (Used Parts)
Examine the seating area of the needle valve for wear or damage. Also examine the needle quill and its 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 stick 6 to 12 times, applying a light pressure with the thumb and forefinger.
FIG. 38. Comparison of former and New Design Injector Parts
Fig. 37. Injector Plunger,
Follower and Relative Location
CAUTION: Be sure that no compound is
March, 1973 SEC. 2.1.