Coil Confusion

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equium

equium

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Oct 3, 2014
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Location
Shingle Springs, CA
1970 Plymouth Valiant 318.
Electronic Ignition (brand unknown, installed by PO)
Orange ECU
Resistor .9 ohms
MSD Blaster 2 coil (PN 8202)
Primary Resistance .7 ohms
Secondary Resistance 5.4K ohms

Problem: Car just shuts off. sometimes at idle or under a load. will start after coil cools
Checked ignition wiring and all looks good.
Noticed the MSD Coil is VERY hot, can not touch.

Called autozone and they verified the specs on OEM coil's secondary resistance should be 10K plus ohms.

I thought my coil was bad, but the readings match what their website says.

Do I put a new (non MSD) coil on? or will that blow something up?

thanks,
Danny
 
I'm not sure how you have it mounted, but you might look at it and see if the wires/posts are toward the bottom. If they are on top they could be out of the oil causing it to overheat.

I have mine mounted upright on the firewall, no issues.
 
I have it mounted horizontally on the Edelbrock intake, just behind the carb.
If all the numbers on the coil are good, could it just be a matter of moving the coil off the intake on mounting it verticle? That easy?

BTW, I have the coil sitting next to me and when I shake it, I hear the oil. I guess that means I have not cooked it all out?

If I bought a duralast gold coil as a backup, it should just be "plug and play" just like the MSD, correct?
 
The 0.9 Ohm ballast is giving a saturation current of about 8.7A. That coil is designed for MSD CD ignitions. A CDI is very short duration at a higher current, so the heating is less. The Mopar box relies on the ballast resistor to limit the current, typically to about 5A. Adding a second 0.9 Ohm ballast in series will limit the current to about 5.5A that might work. While MSD suggests only 0.8 Ohm ballast for conventional ignition, they do not provide primary current rating.

I would not trust a coil that has over heated to the point it stalls. The enamel insulation on the magnet wire used in primary winding is likely failed.
 
My coil gets very very hot also and it's been fine for years, I would start by checking to see if you have about 7 to 9 volts at the coil when it's running, if it's more try a ballast with a higher ohm reading. A lot of the part store ones are 1.5 or so. If your at between those voltages you should be fine coil wise.
 
Thanks for the replies.
My voltage at the resistor was 7.9 and dropped to 7.7 by the time it passed through to wire to the coil.
I picked up a new coil tonight and will install tomorrow.
I need to find a spot on the firewall to mount vertically. everything is in the way!
I'm afraid to go too deep with screws in the firewall for fear of hitting something. lol
Thanks again for the fast response. I'll post an update when it's all back together.
 
You sure it's not the orange box? I had one die on the Barracuda. That's why it now has chrome box.
 
lilcuda said:
You sure it's not the orange box? I had one die on the Barracuda. That's why it now has chrome box.
Click to expand...
It's my understanding that when the Orange (or what ever color) box fails, the engine wont start? Have I heard wrong? I thought I was reading good voltages, but the only two leads I didn't check were the ones going to the dizzy.
 
Get that MSD coil out of there. Stock iginition, stock coil. or you can read this hearsay from another website that mentioned Blaster coils burning up...
"I mounted the MSD coil on the firewall in a horizontal position...However someone just informed me that when he once did the same on his car, the MSD coil burned up and died. He stated that it overheated so badly that when he went to touch it one day, it "Left skin on the coil". He also claimed that when he called MSD about this, they told him that there's an air bubble inside their coils that's formed somehow during operation, and that this so called "bubble" needs to remain on top away from the windings in order for them to keep cool. yet, there was nothing in writing with these coils that I've ever received stating that they shouldn't be mounted in a horizontal position...." It goes on to explain that others have mounted the coils horizontally but place the terminals "side by side" not up and down to keep the cooling oil on the contacts. Sounds like a bunch of bull ( but I do know the oil is to cool the coils) but look on some Old factory RB cars and see if you can see how the coil is orientated in its bracket while its laying on its side.
 
When a coil fails it most often a turn to turn short in a winding. The short happens when the enamel insulation burns on the magnet wire. A turn to turn short cannot be determined with an Ohm meter because the change in resistance is small compared to the tolerance of resistance due to other factors including turn count. Typically the failed indication is a weak red spark.

While the oil helps cool and insulate, hot spots carbonize the oil, that is bad because that conducts. A coil can can only get out so much heat. A chrome plate, heavily painted, or fancy stickers hold heat in.

Pishta is correct, use a stock coil. I go further, use correct ballast too. While ignition energy increases with current squared, too much will burn out the transistor in the mopar box. Transistors have a weakness when used at high temperature, current and voltage. The transistor is rated with perhaps little excess for stock application. Transistors typically short when failed. Low Ohms to ground at the disconnected (-) wire that goes to coil, will identify. Do check with ignition off. An open transistor will not pull coil (-) to ground when ignition is on.

If you really want to diagnose ignitions, a current probe and scope provides more meaningful information than a voltmeter. The voltmeter does not measure the peak current, it give an average voltage for the pulsating signal that also varies with RPM.
 
If it is a round coil i was told they where all made overseas and they are junk .Went through about 5 different brands of round coils got so hot you could not touch them .I put a petronix square coil on mine i never had a problem since
 
I recently installed a complete MSD ignition system. In the coil instructions it says to always mount the coil vertically. On a 340/LA motor you can accomplish this by using a bracket Mancini makes specifically for this purpose.

The coil must be matched to the ignition system. In my case I bought the whole MSD package: distributor, coil, and box. The system I have eliminates the ballast resistor. So far so good.
 
Pishta and Kit have it right; the coil resistance is too low for the ignition system. You need to find a coil that has a 1.5 ohm resistance if you stick with the present system. You would be OK on the drag strip but not on the street. And the orange box just exacerbates that. I would ditch it for a standard box for street use.

You may try the Pertronix Flamethower for a stock replacement with a small amount hotter spark. Get the 1.5 ohm version.

Don't just put a higher ballast resistance on it. The problem with higher resistance ballasts is that the rated resistance is when cold. A 1.5 ohm ballast will be about 5 ohms when hot, and then you will have too high a total resistance and spark will be weak when running a while and at high RPM's.

With the coil being hot, it is likely a combination of a low resistance giving higher current than normal, and some shorted turns in the coil.
 
The orange box on the car was installed by the PO.
This is my son's car and he's not a "hot rodder". I'm OK with switching to a square, e core coil and stock ignition box or stock coil (purchased last night).
so, since this is basically a daily driver, can I downgrade from the orange?
Is it as easy as swapping the ECU and coil? What color ECU should I get?
Additional info: Edelbrock performer intake with Edelbrock 1406 carb. Mild Cam, specs unknown.

Thanks
 
The Barracuda that equium now owns used to be mine. It has had a Blaster 2 coil on it since the early 90s with no issues. Maybe the coil in question is newer and made in China?
 
Hi everyone. I have the new coil installed. I went with a duralast gold for now.
I found some aluminum angle and fabricated a bracket so the coil is verticle.
After spending a record time of only 3 minutes figuring out I forgot to plug in the distributor, it fired right up.
I let it warm up and idle for a good 15 minutes and took it for a run around the block.
No stalling. The coil did get hot, but not super hot like the MSD coil. If this happens again, I'll look into getting an E Core coil. But for now, my son want his car back and my wife wants her minivan back. lol
Thanks everyone for all the help.
Danny

Here's some pics:
 

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I know there are purist out there. However I have always upgraded to a msd 6al with built in rev limiter. Then I have always used the e coil whether it's was msd or in the old days I used ford E coils. The e coil doesn't care what position its mounted. This affords you as well to get rid of the resistor as well. I run this set up on my race and street cars. Side note i run stock distributors in all my cars.
 
Not sure if it is an optical illusion. I see a fray at the (+) coil terminal end wire, that seems to be touching the A/C pipe stub.
 
KitCarlson said:
Not sure if it is an optical illusion. I see a fray at the (+) coil terminal end wire, that seems to be touching the A/C pipe stub.
Click to expand...
Could be an optical illusion. I'll check closer when my son comes home from school. And I'll move the wire away from the pipe to prevent fraying, too.
I did notice, though, when I zoomed into the picture to take a look; the dried on RTV is way more embarrassing than I thought. time for clean up. :)
Thanks Kit, for pointing that out. It's always good to have many eyes on the subject.
 
Find an NOS Standard Ignition Blue Streak coil for a mid 70s Mopar and call it done. That's the style ignition box you have.
 
equium said:
My son came home from school and reported NO Stalling!!
He was glad to be spared the embarrassment.
Click to expand...
My son informed me that on the way home, the car "stalled" for a half second, but restarted on its own. (I don't know if there's a special name for that other than stalled)
I immediately checked the coil. It was warmer than the day before, to the point that I couldn't keep my hand on it.
As I mentioned before, I'm running an Orange ECU and a .9 ohm resistor.
My question is now, am I running the appropriate resistor for the orange box?
This is just a daily driver for my son.
I'm trying to avoid jumping into an MSD box (even though I'm so tempted). lol
Thanks
 
Well, since mine seems to be the only, or one of the only ones that just goes and goes, and goes(15 yrs I think), I guess Ill go out and measure what I got. Be back inabit.

Oh boy, Im in big trouble now. Im going to be saying sorry to a lot of people. Seems I dont have the Orange box anymore. Nor the resistor. Nor the wiring. Its all gone. And at first I couldn figure out what was powering my ignition. Then I found it. Jacobs Opto-Timer; my adjustable timing control. Seems theres an amp in there as well.Oh boy that things been on there since the early 2000s. Maybe 2004ish.I dont even remember pulling the Orange box out! S#*t! Guess I can take the spare parts out of the trunk,then.Wonder what else Ive forgotten.

Yeah, so; To all the dear people on FABO, my sincerest apology. I screwed up. No Orange box for these past 10 or more years. I know Ive been bragging on that box for a while now.So sorry.
 
Try a different ballast resistor. Most of the replacements are 1.5
Ohm and will cut voltage to the cool.
You want about 7 to 9volts at the coil at idle.
 
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