TM-9-2815-200-35 Maintenance Manual for AVDS-1790-2M AVDS-1790-2A and AVDS-1790-2AM Engines Download
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nozzle body over valve and lap valve to seat with a very light pressure for 15 to 20 seconds at 500 to 600 rpm chuck speed. Wash body and valve very thoroughly in clean fuel before assembly. (b) A sticking valve can, in some in- stances, be made to slide freely by cleaning the valve stem with tallow and a felt pad with valve clamped in rotating chuck. If the valve cannot be made to slide freely, the fuel injector nozzle assembly must be replaced. (c) Replace nozzle body and valve assembly when any of the spray holes or the drilled fuel passage cannot be cleaned so that they are free from obstructions. (d) Replace nozzle body and valve assembly when lapped sealing surface of body is badly nicked, scratched, or cracked. Remove minor scratches from sealing surface by lapping with fine lapping compound on a smooth lapping plate. The nozzle body must be held flat on the lapping plate during this operation or the sealing surface will become rounded on the edges. (2) Valve stop spacer. (a) Replace valve stop spacer (L) when lapped sealing surfaces on either end are cracked, deeply scratched, pitted, or when the area around the center hole at nozzle end is worn or pounded beyond 0.003-inch depth. (b) Remove minor scratches and im- perfections from lapped sealing areas on ends of spacer by lapping with fine lapping compound on a smooth lapping plate. The spacer must be held flat against the lapping plate during this operation or the sealing surface will become rounded on edges. (c) Replace valve stop spacer when drilled fuel passages cannot be cleaned so that they are completely free from obstructions. (3) Adjusting spring and spring seats. Replace nozzle opening pressure adjusting spring (N) and spring upper and lower seats (D and M ) when cracked or worn, or when nozzle opening pressure does not meet the limits specified in paragraph 4-17c(2). (4) Holder spring. Replace holder spring (P) when cracked, broken, or when inspection revealed discoloration due to overheating. Replace the holder spring when it does not conform to the dimensions detailed in para. 4- 18c(4). (5) Holder body. (a) Replace holder body (A) when cracked, burred, nicked, or when threads are stripped or damaged. (b) Remove minor scratches and im- perfections in lapped sealing surface of holder body by lapping with fine lapping compound on a smooth lapping plate. The holder and plate must be held 90 degrees to each other. There should be no rocking motion during lapping. (6) Nozzle cap nut. Replace nozzle cap nut (J) when badly nicked, burred, or when cracks are evident due to overheating. Replace cap nut when threads are stripped or damaged, and when gasket area is scratched, nicked, or burred. (7) Nozzle retainer. Replace nozzle retainer (F) when cracked, badly nicked or burred or when hexagon nut area is damaged, Replace retainer when threads are stripped or damaged. (8) Fuel injector tube connector. Replace fuel injector tube connector (Q) when cracked or threads are stripped or damaged. e. Assemble and Test. (1) Assemble. Refer to figures 4-169 and 4- 170. (2) Test. Refer to paragraph 4-17c. The fuel injector nozzle and holder assembly should be tested whenever nozzle has been disassembled. 4-87