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tech supt

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  • tech supt

    any idea possible causes of mis firing of hitachi B&W engine 8L42MC on cylinder no.8
    all was new pumps, liner, piston, rings , injectors. transfer the fuel pump to another cylinder
    but its working.

  • #2
    edgar sy : Further troubleshooting-
    • Check governor linkage to the fuel pump of the affected unit
    • Fuel valve seat on cylinder head must be lapped and check for any leakage signs
    • Check for wrongly adjusted or slipped fuel cam
    • If engine has reversible roller guide, check if it fitted in wrong position

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    • #3
      Locate the fuel header (8 bar?) which feeds all the fuel pumps.
      One end of it will have a pressure regulating valve, the pipe of which will lead up to the FO mixing column.
      I am assuming that the misfiring cylinder #8 is the last cylinder (power take off side?) located close to this pressure regulating valve.
      If so, air is possibly getting trapped at the end of the fuel header, close to the regulating valve.
      (You may notice that the fuel header pipe is slightly at an incline, with the higher end at the regulating valve).
      Normally, the small quantity of air in the fuel header goes to the mixing column and gets vented.
      If it accumulates in the fuel header, it will interfere with the injection / firing of the end cylinder.
      So check
      ​1. How is air entering a pressured line - check the suction side of the FO booster / circulating pumps - loose suction filter covers, worn shaft seals etc.
      2. Drain valve of fuel header pipe (forward) leaking? Is FO leak off tank filling up?
      3. Pressure regulating valve faulty. Use a listening rod to see if it is chattering.
      4. Open vent cock near regulating valve to check for air. Careful - hot oil under pressure
      5. Recirculating valve on mixing column partly shut.
      6. OR FO is being overheated.
      Let me know how you fare

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