My coil keeps going out?

[Violator]

I posted on here about a week ago about a problem I had with my Bronco just dying. I don't want to steal the thread below about my Bronco just turning off. My problem may be a bit more specific. Last week I replaced the ignition coil after getting stranded on the side of the road. I swapped in a good used one just to check if that was the problem and it started right up. I replaced it with a new one and problem solved, I thought. Today, same damn thing happened. Driving down the road and it just turned off. Lucky for me this time I still had the good used coil in the glove box, "just in case". I swapped the coils and it fired right up. I'm not sure how to test to see if the coil is really bad but I did nothing else but swap coils and it runs fine. What possible reason could there be for this? I'm neurvous about taking it anywhere now without a spare coil. Any ideas?

 

[Violator]

I should add that it's a '73 but the PO has upgraded to an electronic igniton. As far as I can tell it's all OEM parts. No aftermarket coil, distributor or ignition box. Just Duraspark ignition parts.

 

[DirtDonk]

Couple of things come to mind. One is that perhaps your coils are not compatible with the specific type of electronic ignition, and/or your resistor wire has been bypassed, causing them to overheat.

The other thing is the wires and connections themselves. Whenever people have this type of problem, it's as often as not, one of the wires deteriorating or a connection doing the same.
I finally found out why mine kept dying by digging into the harness a couple of inches only to find a rusting and loose power connector to the positive side of the coil.

Hopefully yours is that simple. Still takes some work, but doesn't cost near as much as replacing the parts!
Search around here for how to check your coils to see if they're still good (resistance test), which will also be able to tell you if a specific coil is compatible with your ignition or not.

What type of ignition setup are you running?

Good luck.

Paul

 

[Violator]

From what I can tell it's all factory style Duraspark parts. The coil that went out last week has been in there since I bought the Bronco about 12 years ago. It's been fine up until last week and then again today. I just figured that electronic parts have their lifespan and that it had finally just had enough.

 

[Violator]

I also inspected the connection down in the coil where the plug wire plugs into and there was no sign of fouling or anything at the coil end. Still looks brand new. Also at the distributor cap end everything looks clean with no soot or fouling.

 

[Violator]

Just found something, not sure if it's related. I'm using the factory style wiring to the coil. It has the white plastic clip that snaps onto the coil. The coil has the studs not the threaded posts. On the connector end there was a male end of a wire that has never been connected to anything. I just noticed that on the good used coil I put in there is a female end that matches the wire not used before. That wire is connected to some sort of resister type thing. Is that for the radio noise or is that of some importance? I have a similiar resistor connected to the voltage regulator also. Should I hook this up or leave it the way it was?

 

[ryan287]

I heard that some coils are not designed to lay on their sides - I guess the oil inside drains to one side, which allows the overheating of the coils that are no longer submerged. I have had an MSD barrel style coil for a few years mounted on the side with no problems.

 

[Violator]

Worth a try ryan. Mine was in fact mounted laying on its side through a hole on the end of the right side head. It was a stock replacement from Advance Auto and it's oil filled. Maybe I should try a MSD that is epoxy filled.

 

[Viperwolf1]

My guess is the ignition resistor wire has been bypassed.

 

[Violator]

Where is the ignition resistor located? Is it connected to the coil? Is this the connection that I made with the unused wire from the white clip on connector to the resistor on the coil?

 

[Justafordguy]

The stock resistor is built into the wiring harness. The best way to tell if it's ok is with an ohm meter. It should be about 1.1 - 1.3 ohms.

 

[gledhillt]

Had the same problem. I put a inline resistor on, got it at the parts store. Took care of the problem.

 

[Ranchtruck]

It's often referred to as a ballast resistor. It cuts the voltage at the coil from 14v down to 9v, so the coil doesn't have as much current running through it.

There's often a resistor bypass wire that comes from the starter solenoid. That feeds full battery voltage to the coil while you're cranking the engine to make up for the battery voltage getting pulled down by the starter.

Duraspark needs full battery voltage to the module, but not to the coil. The coil still needs the ballast resistor.

 

[patterdale]

I have read here that you should measure the resitance of the resistor wire and get an ohm reading. The easiest is to measure the voltage at the + side of the coil. If it is more than @ 9 volts you either need a ballast resistor in the line to the coil or just replace it with one that does not need a resistor. They are commonly talked about as "internally resisted" and some will argue there is no such thing. They work well in most applications. One never knows with these 40+ year old beasts what any PO has done. If you have anything more than 9 volts to the input side of the coil something has to be done to reduce the voltage.

 

[motoman]

Worth a try ryan. Mine was in fact mounted laying on its side through a hole on the end of the right side head. It was a stock replacement from Advance Auto and it's oil filled. Maybe I should try a MSD that is epoxy filled.

I had the same issues with mine on it's side..... work fine for a bit and die....I wanted to keep mine on its side so I bought a MSD Epoxy Coil and never had the problem again.

The OIL coil will overheat laying on its side.....

 

[Viperwolf1]

I have read here that you should measure the resitance of the resistor wire and get an ohm reading. The easiest is to measure the voltage at the + side of the coil. If it is more than @ 9 volts you either need a ballast resistor in the line to the coil or just replace it with one that does not need a resistor. They are commonly talked about as "internally resisted" and some will argue there is no such thing. They work well in most applications. One never knows with these 40+ year old beasts what any PO has done. If you have anything more than 9 volts to the input side of the coil something has to be done to reduce the voltage.

That only accurate way is to use an ohmmeter. Voltage is deceptive in open circuits. Don't trust it.