378 Diesel Engine Technology Copyright Goodheart-Willcox Co., Inc. 4. Soak the nozzle holder in a carbon-removing cleaning agent for at least four hours before removing the nozzle cap nut. If this is not done, the nozzle locating pins may be damaged during disassembly. 5. Mount the recommended fixture in a bench vise and assemble the appropriate insert to the fixture holding plate, Figure 18-18. Note: Some holders have a mounting flange and do not require an insert. The flange engages the holder bracket pins. 6. Assemble the holder assembly to the insert and engage the appropriate box-end wrench to the nozzle cap nut. 7. Adjust the fixture clamping plate so that the clamping bolt engages the nozzle tip. Secure the plate in place and tighten the securing bolt to a torque of about 20 ft-lbs. (27 N•m). 8. Loosen the cap nut with a box-end wrench until the nut can be turned by hand. A blow to the end of the wrench is recommended to break any carbon bond between the nozzle and cap nut. On some nozzle holders, it may also be necessary to loosen the adapter and back off the pressure adjusting screw at the top of the holder. 9. Remove the holder assembly from the fixture. 10. Remove the cap nut, nozzle spacer, and nozzle from the holder body, Figure 18-19. 11. Remove the spring seat, spring, and spacers from the holder body. Take care not to lose the spacers. Cleaning While keeping each valve with its original nozzle body, soak all parts of each nozzle in a varnish-removing cleaning agent. The disassembled injector may also be cleaned in a 15% caustic soda solution, an air agitated solvent tank, or an ultrasonic cleaner. If the valve nozzle cannot be easily removed after soaking in a carbon solvent, a hydraulic nozzle valve extractor should be used. Apply hydraulic pressure from the nozzle test stand to force the valve out of the nozzle body. Caution: Do not intermix nozzle valves. Begin by cleaning the needle valve with a brass wire brush and then use a soft brass tool to remove any carbon from the tip or tip area. Clean the needle valve with mutton tallow placed on a soft cloth or felt pad. Check the valve assembly for pitting or discoloration, Figure 18-20. Holding fixture Nozzle cap nut Box wrench Pins Clamping plate Figure 18-18. Nozzles are mounted in a special holding fixture to make disassembly easier. (Navistar International Transportation Corp.) Magnifying glass Plate Nozzle valve body Nozzle valve Figure 18-20. Injector parts must be closely inspected for nicks, scratches, or signs of corrosion. (Detroit Diesel Corporation) Installation (copper) washer Nozzle cap nut Nozzle body Nozzle valve Assembly Intermediate disc Spring Shim Nozzle holder Retaining collar-nozzle holder Spring seat Figure 18-19. Exploded view of a fuel injection nozzle and components. (Mack Trucks, Inc.)