Ignition Coil very hot and engine won't start? - Pirate4x4.Com : 4x4 and Off-Road Forum
 
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Old 07-22-2003, 10:34 PM   #1 (permalink)
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Ignition Coil very hot and engine won't start?

Ok, its not a 4x, it is a marine application, but its a ford anyway its a ford 351 windsor, 4barrel 275 hp, with an ancient ignition system.

motor is an 83, but the ignition reminds me of 60s vintage, breaker point dist, and a coil.

The problem is when it gets H-O-T, after it is shutoff it won't start again for an hour or so.

after sitting a while, it starts and runs great. Got fuel, but no spark.

I'm guessing it is a two-fold problem of a weak coil, and alot of cranking amps because the motor is hot and ???

Ok, now my questions:

1) other than the coil is there anything else in the ignition that is heat sensitive?

2) assuming it is the coil, whats a good hi-temp coil.

3) breakerless ignition is an option, just spendy for the marine duty ones, and it runs fine with points. max RPM is about 4400, and that's well past the limits of the prop anyway.

4) I vaguely recall a ballast resistor on one of my old cars ( can't remember if it was ford or GM though) that would give 12v across the points, and less as it warmed up. this was supposed to help a cold start, but if it got too hot, could it affect a hot start.


Yes I had plenty of fuel, had fuel at the carb (accel pump squirted as normal) and I even tried starting fluid. It did not appear flooded. I did prop open the throttle at one point for about 15 mins, but it wouldn't fire after that either.

each time it failed, the coil was too hot to touch, and seemed hotter than the valve covers. overall the engine wasn't that hot, but the ambient temp under the motor cover was probably 250+

Next time I'll have a timing light and a dwell meter and a multi meter with me, but before then I'd rather shotgun fix the suspect parts and hope not to use them.

any ideas?

- Dan (who tossed all his old repair manuals )
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Old 07-22-2003, 11:22 PM   #2 (permalink)
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You need a Ballast resistor or a resistor wire in order to run a points ignition. Without it you will run too much current thru your points/coil. This usually just burns up the points though.
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Old 07-22-2003, 11:38 PM   #3 (permalink)
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is a ballast resister a coiled wire in a piece of white porcelin?

Like a rectangle 3/8" square, two inches long?

If so it has one. Can these go bad?
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Old 07-23-2003, 08:35 PM   #4 (permalink)
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Yes, ballast resisters can, and do, go bad I've had it happen to me before. Under hot start (and cold) conditions you need full battery voltage to the coil but, when the resister's hot, of course, you won't. Here's an idea: use a normally open relay to bypass the resister to get full voltage to the coil at start up only, by wiring the relay so it's energized only when the starter's cranked. After the starter stops the relay goes back to open and current flows back through the resister. Works really well Oh, yeah, I hope that made sense
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Old 07-23-2003, 10:05 PM   #5 (permalink)
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yeah it made sense.

thanks.

I'm considering solid state ignition, but a short term fix would be good
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