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Foxbody Ignition Miss Help!!


Guest jbird79

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I have a 91 GT with a 347 stroker... it has full MSD ignition.. It started having an ignition miss at high rpm's Thursday.. I drove it home last night, and it continued to get worse.. When I pulled in it died, and now it wont start.. it will try to fire, and it backfired through the exhaust... the plugs are autolite 3924's, and are about a year old... Does anyone have any idea's???
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It sounds like the coil failed. It's common with MSD boxes because they hit the coil with 375 volts and not the 12 volts alot of coils are designed for. Some coils even say they can't be run with a capacitive discharge ignition system. Short of that, I have a couple MSD 6 boxes that are good, as well as coils that you could use to check it. I also repair MSD boxes, except for the NASCAR specific ones (they are filled with an epoxy that has be to soaked off in acetone).

 

My guess is that you went out and got an MSD box, installed it per the instructions with the white wire feeding from the coil feed out of the ford factory system and used the factory coil. The factory coil is not designed to be hit with the voltage an MSD puts out and it failed. The only way to check the coil is with a low ohm meter, because a regular meter, even a digital will not read the 3 ohms that the primary side should read. The secondary will read about 1200 to 1500 ohms and can be checked with a digital meter though. One other possibility is to temporarly disconnect the MSD and reconnect the Ford ignition to the coil and see if it runs. This would only be possible if you didn't eliminate it. (which I do, two seperate ignitions, one feeding the other is a troubleshooting nightmare) Call me at 989-2459 and I can talk to you about this more or if you have quesiotns feel free to ask.

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