Keep burning up coil

[orange69]

Ok guys, I'm getting desperate for some help. I keep burning ignition coils. Here's some specs:

351W, Crane Cams XR-1 electronic ignition, stock coil, 3G alt.

I have replaced the resistor wire, tested voltage (7 volts) thought everything was good then smoked a coil. Installed a ballast resistor, tested voltage (7 volts) then cooked another coil! I've tested the running/charging voltage at battery and it's around 14.5-7. I thought that seemed a little high so I had it tested at NAPA and they say its fine. Talked to a mechanic and he said to make sure all your grounds are good. So I cleaned all the grounds going to engine. Battery cables are clean and look good. I put in a new ignition switch a while ago. Replaced wiring from starting solenoid to ign switch and to coil. I have one wire running from solenoid to coil (for 12v on startup), then another from ignition switch (using existing resistor wire) to ballast resister then to coil +. Yes I'm using both resistor's now.

So on first startup, electric choke works fine (it's also hooked to starter solenoid where the coil is hooked to, been this way for years) so it idles around 1100 rpm. Voltage at coil reads 7.5. After it warms up I bump the throttle and it idols around 650-700 rpm. Check voltage again and it starts climbing to 8, then 8.5 then 9 then 9.9 so I turn engine off. So I disconnect the alternator and try again. Voltage at coil is 6.5. I let it run for a while and it starts to run a little ruff. A quick bump of throttle and it stumbles a little. After its good and warm I check voltage and it goes up to 7. Hook up alternator and it runs smoothly again. Voltage at coil is over 9 volts now. So is my alternator putting out too much voltage when it gets warmed up?

I've double checked the Crane Cams XR-1 electronic ignition and it does require resisted voltage. It hooks directly to coil + and -. It's been on for several years with no issues. I have not tested the spark plugs wires. They're several years old, but it runs great. The coil is just a stock replacement from local auto parts store that requires resisted voltage. I also have a tach hooked to it, not sure if that could cause any issues.

I'm at a loss at this point. Not sure what to try. A new alternator, new ignition system? Sorry for the long post.

Thanks

 

[B RON CO]

Hi, I call crane and see what coil their tech guys recommend. If you have a tach disconnect it for now. Good luck

 

[SHX669]

By " burning up coils' do you mean they get hot an quit working ? - and hot enough to distort the housing ? Or do you mean they just quit working ?

 

[blubuckaroo]

I've had to replace several coils too.
It would always happen when the kids used the car and sat listing to tunes with the engine off and the ignition switch in run rather than in the accessory position. Coils hate that, and will fail pretty quickly if energized with the engine not running.
The coil failure was always obvious. The little bellows on the bottom would bulge out.

 

[welndmn]

Why if your voltage changing?
It should be 9V at all times (outside of starting, where it should spike to 12v to aid in cold starting)
You have something wired incorrect.
The starter solenoid is where I would start.
http://www.bronco.com/graphics/diagrams/68-71ignition-color.gif

 

[orange69]

Thanks for responses. I called Crane Cams and they no longer deal with these ignitions, they told me to call Fast. Called them and they say there's no "field testing" that I could do. They said the electronic module would more than likely fail before the coil would.

And when I mean it burns up is probably not the best description. It just stops working.

 

[orange69]

So I disconnected the electric choke, tach, and 12V starting wire from starter solenoid. Hooked choke up to battery directly (just for testing). Started bronco and measured voltage at coil+ and it was 11.6V. I then measured voltage on the resister and it was 13. something on one side and 11.6V on the other. I thought it should be around 8-9V. Ohm out resister with wires disconnected and it was 2.5ohms. Checked Crane Cam directions and it said to use a 1.2-1.5ohm resister (Chrysler CR107). So I run to store and buy one and it didn't make any difference. It still read 11V. So why are these resisters not working? Am I taking measurements from the wrong spots. I take red+ lead from multimeter to coil+ and black- to ground.

 

[Justafordguy]

Sounds like you're testing correctly. I have noticed that the voltage will be a little higher on the coil when you first start it up. After the engine warms up (actually it's the resistor that is warming up) a while the voltage will be lower.

 

[orange69]

Update: I finally got it figured out. It was the Crane Cams XR-1 module. After trying several more things I finally put in a set of Accel Electronic Points. It was funny because when I went to start it, it would fire right up in the start position. But when it switched to the run position it would die. After more troubleshooting I measured the voltage at the coil + and it only had 2 volts! I checked voltage on the "input" side of the ballast resister and it was only 7! So that meant bolt resisters (the resister wire and ceramic resister) were doing what they were supposed to. Of course now I only needed one. So I bypass the ceramic resister and it starts and runs better than ever! WooHoo! Man that gets so frustrating at times. It had left me dead in the middle of the road one to many times, to the point I didn't want to drive it anymore. Now I can finally enjoy the new power brakes and Spartan locker I put in a few months ago.