DETROIT DIESEL 53
Fuel Injector 2.1.1
a former injector if a new design spray tip assembly is used.
Place the spring cage, spring seat and valve spring assembly (valve spring down) on top of the check valve
CAUTION: When installing a new spray tip assembly in a former injector, a new valve spring
seat must also be installed. The current needle valve has a shorter quill.
Insert the needle valve, tapered end down, inside of the spray tip (Fig. 2). Then place the spray tip and needle
valve on top of the spring cage with the quill end of the needle valve in the hole in the spring cage.
Lubricate the threads in the injector nut and carefully thread the nut on the injector body by hand. Rotate the
spray tip between your thumb and first finger while threading the nut on the injector body (Fig. 39). Tighten the nut as
tight as possible by hand. At this point there should be sufficient force on the spray tip to make it impossible to turn with
Use socket J 4983-01 and a torque wrench to tighten the injector nut to 75-85 Ib-ft torque (Fig. 40).
NOTE: Do not exceed the specified torque. Otherwise, the nut may be stretched and result
in improper sealing of the lapped surfaces in a subsequent injector overhaul.
ASSEMBLE PLUNGER AND FOLLOWER
Refer to Fig. 37 and slide the head of the plunger into the follower.
Invert the injector in the assembly fixture (filter cap end up) and push the rack all the way in. Then place the
follower spring on the injector body.
Refer to Fig. 41 and place the stop pin on the injector body so that the follower spring rests on the narrow flange
of the stop pin. Then align the slot in the follower with the stop pin hole in the injector body. Next align the flat side of the
plunger with the slot in the follower. Then insert the free end of the plunger in the injector body. Press down on the
follower and at the same time press the stop pin into position. When in place, the spring will hold the stop pin in position.
Check Spray Tip Concentricity
To assure correct alignment, check the concentricity of the spray tip as follows:
Place the injector in the concentricity gage J 5119 as shown in Fig. 42 and adjust the dial indicator to zero.
Rotate the injector 360' and note the total run-out as indicated on the dial.
If the total run-out exceeds .008 ", remove the injector from the gage. Loosen the injector nut, center the spray
tip and tighten the nut to 75-85 lb-ft torque. Recheck the spray tip concentricity. If. after several
Fig. 43. Relationship Between Exhaust Valve Bridge and Valve Stems