Diesel Engine Troubleshooting

Detroit Diesel Injector Troubleshooting

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To determine if repair is possible or replacement is necessary perform the following procedure.

Flowchart for Repair or Replacement of Electronic Unit Injector

To remove the injector, complete the following steps: ?

  1. Loosen the injector wire terminal screws two full turns and remove the terminal wires.
  2. Remove injector hold down crab.
  3. Lift the injector from its seat in the cylinder head by inserting a pry bar under the injector body.
  4. Cover the injector hole in the cylinder head to keep out foreign material. Remove carbon from the injector exterior in the area where the tip joins the nut, using wire buffing wheel, J 7944 .

Disassembly of Electronic Unit Injector

On a Series 60 engine EUI, only the injector solenoid and seal rings are serviceable. The injector must not be disassembled. ?

Inspection of the Electronic Unit Injector

To clean and inspect the injector, complete the following steps: ?

  1. Clean the exterior of the injector with clean solvent and dry it with compressed air.Note: Do not test new or reliabilt ® remanufactured electronic unit injectors prior to installation in the engine. The Kent-Moore ® POP stand should only be used as a diagnostic tool on fuel injectors that have been removed from an engine.
  2. Test the EUI using J 34760 . Follow procedures supplied with this tool. Reuse or replace injector or injector and solenoid as indicated by testing.
  3. Inspect the O-rings for damage or foreign material. Replace O-rings.
  4. Inspect the fuel injector tubes at the injector seat. If required, replace the fuel injector tubes.

Repair of Electronic Unit Injector Solenoid and Seals

Perform the following steps for solenoid replacement: ?

  1. Loosen the injector wire terminal screws two turns and remove terminal wires.
  2. Loosen four hex-head screws and remove old solenoid.
  3. Perform the appropriate step for the DDEC unit used. For DDEC I and DDEC II, discard the solenoid, load plate, follower retainer, and screws. Do not reuse old screws. For DDEC III/IV, discard the solenoid, follower retainer, and screws. Do not reuse old screws. The load plate must be reused.
  4. Remove spacer and seals from injector body.
  5. Discard seals, but do not discard spacer.
  6. Install new seal in spacer groove and position spacer on body with seal facing down. Seal may be retained in groove with small quantity of grease.
  7. Install new seal in solenoid groove.
  8. Install solenoid on spacer.
  9. Install new screws through the load plate and follower retainer, solenoid, and spacer.
  10. Thread screws into body and tighten all screws until heads contact retainer and load plate with a slight force (less than 0.6 N · m [5 lb · in.] torque) in the sequence shown.
  11. Torque screws to 2 N · m (19 lb · in.) in the sequence shown.
  12. On DDEC II injectors only, etch the last four digits of injector part number on the load plate.

Installation of the Electronic Unit Injector

Perform the following steps: ?

  1. If the fuel system is contaminated with coolant:
    1. Drain the fuel tanks and refill with clean fuel.
    2. Replace both filters with new, and clean the fuel/water separator, if equipped.
    3. Inspect fuel injectors for damage and replace as required.
  2. If the coolant system is contaminated with fuel, flush and reverse flush the system.
  3. Using clean compressed air, blow out any fuel remaining in the injector bore.
  4. Detroit Diesel encourages the use of an additional service seal (5104701) that is impervious to both coolant and fuel. This seal should be used in situations where injector tube seal leakage or deterioration is suspected or confirmed. Place the auxiliary seal in the injector hole and seat it against the top of the injector tube with a 41.3 mm (1-5/8 in.) diameter wood or plastic dowel.
  5. Check to make sure the injector bore is thoroughly clean.
  6. Apply a thin coat of clean ethylene glycol to the injector seal rings and install them in the injector nut ring grooves. Make sure seals are properly seated.
  7. Insert the injector into its respective injector tube bore. Visually align the injector body for equal clearance between valve springs (there is no locating dowel pin on the underside of the EUI). After locating the injector, press down on the top of the injector body with the heel of your hand to seat it in the injector tube.
  8. Determine which type of hold-down crab is used by measuring the overall height.
  9. Position a 0.762 mm (0.030 in.) feeler gage between the crab and injector spring on the side of the spring that faces the intake manifold.
  10. Install the hold-down crab, hemispherical crab washer (flat surface up against bolt) and hold-down bolt to the injector. Ensure the clamp does not interfere with the injector spring or valve springs.
  11. Torque the hold-down bolt to 58-66 N · m (43-49 lb · ft).
  12. Install the EUI terminal wires by positioning the keyhole in the terminal over the screw in the injector solenoid housing. Pull the terminal end down so that the screw rests in the smaller slot in the terminal. Torque the terminal screws to 1.08 – 1.13 N · m (9.5 – 10.0 lb · in.). Do not bend the terminals down after installation.
  13. Install the rocker arm shafts, with rocker arms in place.
  14. Adjust the intake and exhaust valve clearances and injector height. 
  15. Install the inlet and outlet fuel lines to the fittings at the rear of the cylinder head.
  16. On DDEC III/IV engines, record the injector calibration code from the load plate with the proper cylinder location.
  17. Install the valve rocker cover.
  18. For one-piece valve rocker cover. For two-piece and three-piece valve rocker cover.
  19. Verify repair of electronic unit injector.

Written by Ed

October 24th, 2011 at 3:45 am

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