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I'm a bit concerned about the two recent engine fire stories. I posted my thoughts on the latest thread about this (http://www.brickboard.com/RWD/index.htm?id=833727&show_all=1) but I'd like this out here for some thought and comment. As I noted, I had the "engine died but it was cranking and wouldn't stop" sydrome strike a while back in my 1980. I was sure the problem wasn't in the under-the-front-of-the-engine wires because I had just had those wires out tracking down an alternator failure (turned out to be a broken brush holder to brush lead that time). The previous owner had paid a shop to repair the wires there: they were in good condition and I had put a new loom cover over them before putting them back in place. As I have said, my first defense was to use the battery disconnect switch (not everone has one) and then temorarily ran with the solenoid deactivated. My theory was that the ignition switch's bad behavior had progressed from not always completely engaging the run position after releasing the key (had to sometimes manually turn back a bit more to engage wipers, heater fan, turnsignals, everything but what it takes to run the engine) and now was leaving the starter solenoid connected after the key was released. It hasn't relapsed since I replaced the switch.
I can see how having the insullation chafe through on the main lead from the alternator to the battery (via the starter solenoid terminal) whould arc and start a fire especially if there was oil from a leaky front seal. After all, you can weld with a battery. But I don't see how that would keep the engine cranking. I can imagine the lead from the switch to the starter melting down and starting a fire if it was continuously energized since I don't see any fuse in the diagrams.
Is it possible that if the solenoid stays engaged while the engine is running there could be enough of a draw on the alternator to melt the main lead, especially if the insulation was already degraded with cracking and oil? If so , maybe we ought to think of the common partial failure of the ignition switch as much more than a nuisance.
(Remember, crappy insulation blows 747s out of the sky.)
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