What type of ignition setup are you using? People have experienced this after converting to full MSD setups. There is a diode that needs to be installed to prevent this. Also the fans sometimes produce enough juice to keep it running. I am no expert on this, but if you did change to an MSD setup you could search this forum, it has been addressed here. If you use the search funtion type in "diode" and you get about a dozen responses.
Good luck
Gary #06984
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