TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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b. Cleaning. Note. D O not remove carbon from the valve, (K-2, figure 4-170), or inner surface of nozzle body (K-1 )with a sharp tool, abrasive material, or steel wire brush, as these implements and materials will severely damage the highly polished surfaces. (1) Fuel injector nozzle assembly. Soak nozzle body in carbon removing solvent to remove major carbon deposits. Remaining carbon deposits should be removed using a soft cloth or felt pad and mutton tallow. A piece of soft wood, soaked in oil may also be used as a carbon remover. (2) Nozzle body spray orifices. Clean carbon from the orifices of the nozzle body by soaking nozzle body in a carbon removing solvent only. Do not attempt to clean orifices with cleaning wire as this method will distort nozzle orifices and also may block opening due to wire breakage. It is difficult and often impossible to remove broken pieces of wire. (3) Fuel injector holder and associated parts. Clean all parts thoroughly. Be sure hands are kept free from accumulation of grease which will cause collection of dust and grit on parts. Cover or wrap all parts after cleaning to protect them from dirt accumulation. c. Inspection. (1) Nozzle body and valve. Inspect seat of nozzle valve (K-2. fig. 4-170) for evidence of wear, distortion of the valve seat due to pound- ing, discoloration due to overheating, and pitting. Inspect the valve stem between seal and shoulder for scratches and discoloration. Check fit of valve in nozzle body by lifting the valve about one-third of its length out of the body. The valve should slide back to its seat without aid when the assembly is held at a 45 degree angle. Mark sticking assemblies for repair. Inspect the eight spray orifices in the nozzle body tip and the drilled passage in the body for freedom of ob- structions, Inspect lapped sealing surface of valve body for scratches, discoloration, and cracks. Inspect nozzle body valve seat, using a strong light and a magnifying glass (5 to 7 power magnification minimum) for scratches, discoloration, wear, pitting, and evidence of pounding. Note. An otoscope, such as used by physicians for examination of the inner ear, is well suited for this purpose. (2) Valve stop spacers. Inspect the lapped sealing surfaces on the ends of the valve stop spacer (L) for scratches, discoloration, and cracks. Inspect the area around the center hole on the nozzle end for evidence of wear and pounding by the nozzle valve. Maximum allowable depth of wear or pounding at this area is 0.003-inch. Inspect drilled passages in spacer for obstructions. (3) Adjusting spring and spring seats. Inspect the nozzle opening pressure adjusting spring (N) and spring upper and lower seats (D and M) for cracks and evidence of wear. (4) Holder spring. Inspect holder spring (P) for cracks, and for evidence of discoloration due to excessive heat. Inspect free length of holder spring. Limit should be from 1.403 to 1.409-inch when the new copper gasket, FSN 5310-861- 1406, is used. If the old copper-asbestos gasket is used the limit should be 1.407 to 1.409-inch. (5) Holder body. Inspect the holder body (A) for cracks, burs, nicks, and raised metal. Inspect lapped sealing surface for scratches and discoloration. Inspect the threaded area and tapped openings for stripped or damaged threads. (6) Nozzle cap nut. Inspect the nozzle cap nut (J) for nicks, burs, raised metal surfaces, and for cracks due to overheating. Inspect threaded area inside nut for stripped or damaged threads. Inspect the gasket area on end of nut for deep scratches. (7) Nozzle retainer. Inspect the nozzle retainer (F) for cracks, nicks, burs, and raised metal, and for rounding of the hexagon nut area. Inspect threaded area for stripped or damaged threads, (8) Fuel injector tube connector. Inspect the fuel injector tube connector(Q) for cracks and for stripped or damaged threads. d. Repair. (1) Nozzle body and valve. (a) Replace nozzle body (K-1, figure 4- 170) and nozzle valve (K-2) when body seat or valve seat is badly worn, pounded, or pitted, or when nozzle does not conform to spray pattern limits specified in paragraph 4-17c(3). Minor discoloration or imperfections of body and valve seat can be cleaned up by lapping the valve into the body. Clamp valve by its stem in jaws of rotating chuck. Place a very minute quantity of fine lapping compound on tip of valve. Slide 4-86