DETROIT DIESEL 53
Fuel Injector 2.1.1
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 screw driver and withdraw the pin
(Fig. 11). 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. 12), replace the plunger and bushing assembly.
5. Reinstall the plunger, follower and spring.
NEEDLE VALVE TESTS
Remove the injector nut and remove all of the parts below the injector bushing as outlined under Disassemble Injector.
Clean all of the carbon off of the spray tip seat in the injector nut as outlined under Clean Injector Parts.
If the spray pattern test indicated that tip cleaning is necessary, clean the carbon from the tip cavity below the needle
valve and orifices as outlined under Clean Injector Parts.
With the injector nut and spray tip cleaned, assemble the check valve, check valve cage, spring, spring seat, spring
cage, needle valve and tip assembly on auxiliary tester J 22640 (Fig. 13). Carefully pilot the injector nut over the spray
tip and valve parts and thread it on the body as shown in Fig. 13. Tighten the injector nut to 75-85 Ib-ft torque.
Install the shield in the auxiliary tester as shown in Fig. 14 and operate the pump handle until the spray tip valve has
opened several times to purge the air from the system.
Operate the pump handle with smooth even strokes (40 strokes per minute) and note the pressure at which the needle
valve opens. The valve should open between 2300 and 3300 psi. The opening and closing action should be sharp and
produce a finely atomized spray.
If the valve opening pressure is below 2300 psi and/or
Fig. 18. Setting Comparator Stroke Counter
Fig. 17. Placing Injector in Comparator J 7041
March, 1973 SEC. 2.1.1
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