[The Kook Abides]

Sounds like a wiring error. Do you have an engine room fire extinguisher system? That should be wired to shut off both engines in the event of a fire so that your extinguishing agent is not inhaled and consumed by the diesels. Perhaps the error is in this circuit. Sounds like you need a GOOD tech that knows his stuff, not just a 12 volt man.  Capt. George

Thanks for the insight to the fire system.  I will report back next week when I get to work on this.