Coil frying?, Any electric gurus out there? Options

[kart54]

I posted this in the garage section and got no response so I thgought I would try here. Working on the race car last night I flipped my main power switch to test something else I was doing. After a couple of minutes I heard the oil in the coil making noise. When I jumped out of the cockpit and went to the engine compartment I found the coil was so hot it burned my fingers.
What will cause a coil to burn like that? Is it a fault within the coil itself or something external?
The coil was an MSD blaster 2 and my ignition is a Crane XR700 optical with rev limiter.
I went out today and got a new coil but I want to make sure I'm not going to fry this one as well by just installing it. Anything I should check first?
Any help greatly appreciated.
Thanks
Randy

[Matt Romanowski]

I have no experience with the crane system, but is it likes points were you can't leave the ignition on?

If everything was fine before, I would guess that it was triggering the "points" and that is what fried the coil. I'm sure there are people here better at electronics than me. Hope this helps.

[byndbad914]

I posted this in the garage section and got no response so I thgought I would try here. Working on the race car last night I flipped my main power switch to test something else I was doing. After a couple of minutes I heard the oil in the coil making noise. When I jumped out of the cockpit and went to the engine compartment I found the coil was so hot it burned my fingers.
What will cause a coil to burn like that? Is it a fault within the coil itself or something external?
The coil was an MSD blaster 2 and my ignition is a Crane XR700 optical with rev limiter.
I went out today and got a new coil but I want to make sure I'm not going to fry this one as well by just installing it. Anything I should check first?
Any help greatly appreciated.
Thanks
Randy

Randy, coils should be switched only with the ignition and pretty much that means the car should be starting. By leaving the coil on with 12v running into it and nothing to break the ground (the coil was able to ground out to a spark plug because the dist wasn't turning), the outter windings were sitting at 40,000V and began boiling the oil inside it. At that point it is fried quite literally.

Make sure you only power the coil when you are actually ready to start the car in the future. I have a toggle switch mounted right by my key - I turn the key to run the engine on the starter until oil pressure comes up, then while still holding the key I flick the switch with my index finger to relay 12V to both the coil and the ignition box and the car fires up.

edited to clear up bad previous editing - hahah

[McMark]

I'll have to disagree and post an alternate explaination.

Your Crane must have been lined up just so to create a closed circuit. When the engine is running the crane opens and closes the ignition circuit to create the spark. Normally when the engine is stopped your crane will be in the 'open circuit' position. Occasionally the crane trigger wheel will stop with one of the windows lined up with the trigger. This will close the circuit and allow electricity to flow. So when you turn the key on, you're pumping current/electricity through the coil, basically creating a short to ground. Because the coil is the highest resistance piece in that circuit, it will build up the most heat. If you're crane trigger wheel had stopped in a different spot, you wouldn't have had a problem.

I make a habit of unplugging the coil power when I'm going to be turning the key on for long periods of time.

[byndbad914]

(IMG:style_emoticons/default/agree.gif) I edited that a few times trying to make it clear and made it worse, I meant to say couldn't "break" ground (not "make" ground) and so forth. McMark is correct and even managed to explain it clearly. (IMG:style_emoticons/default/headbang.gif) You weren't able to break ground so you had a constant flow is what I meant to say and McMark is right, that is a VERY rare case that all is aligned.

You must have bad luck like I do as I burnt one up years ago for the same reason - I had the ign switch on and messing around and had the same thing. In fact when I pulled the coil wire the tower cracked into pieces is was so brittle from the heat and constant current flow.

[McMark]

(IMG:style_emoticons/default/thumb3d.gif)

[kart54]

Thank you both very much for your responses and your clear explanations. I've gotten a new coil and will be installing it this weekend.
Have a great weekend everybody.
Randy

[kart54]

It Lives. The new coil is in and the car fired right up. Nice to hear the open exhaust again (wife didn't appreciate it and neither did the neighbors but I don't really care at this point.) I'm amazed, you guys were right. I'm not amazed you were right just that the optical trigger managed to get in just the right position to fry the coil. It was completely fried toooo!!! when it came out it fell into two pieces.
Thanks again for all the help!!
Going out to defend the title this year and race a few national races as well. Car seems to be ready to go. All the new stuff is in. I'll tell ya what, it's hard to get in and out that little bitty window opening with a full containment seat installed but the new seat is very comfortable. Can't wait to try it on track.
Any of you so cal porsche guys make it to an SCCA race look me up. For the first time with this car I'll have a pit crew this year so that should mean a little more free time. Car has a new paint scheme on it when I get a chance I'll take some pictures and post them.
As I'm writing this there is one of the new VW adds on. "unpimp my ride" Love em. very funny
Randy
"Car 54 Here I Am" G prod 1.7 liter fuel injected Porsche 914