Burning coils

[ALAN FAIRCLOUGH]

My 1926 Tudor has been modifies with a distributor and coil. I get anywhere from 5 to 1 mile and it stalls and will not statrt. No sparks. I have burnt 5 coils so far. What can cause the coil to die?

[speedytinc]

Excessive heat will do it. I have not heard of this happening this quickly.
Do not mount the coil over the exhaust manifold. Best to not mount right under the top of the hood either.
I like mounting a coil low off a generator mount bolt.
Thats about the coolest place I can think of.
Buy a quality coil like a Bosch. Many of the Asian import ignition parts, like condensers, have a high failure rate from being poor quality.
Sounds/acts more like condenser failures, but you ruled this out?.

[Charlie B in N.J.]

6 or 12 volt? Are you buying the correct voltage coil for whatever your car is using? Now I don’t believe it’s possible to burn out a coil that fast if you’re not using a resistor in the circuit but it sure as heck helps. When buying a coil make sure you get one with a built in resistor. If one’s not available built in add one on the feed side of the circuit. Another thing: unless you’re mounting the coil on the exhaust manifold (and I know you’re not. Just busting chops), it’s really really hard to cook a coil. Traditionally they’re mounted right on the block somewhere with seemingly no regard for generated heat leading me to think something else is going on. Like a 6 volt coil being used on a 12 volt system.

[got10carz]

I'm wondering if the condenser is bad, masking as a coil. By the time you go get a coil, the condenser is cooled off, allowing the car to start.

[big2bird]

1) Excessive hold current.
2) incorrect coil
3) P.O.S. coil. Yes, they are out there now. MSD red coils are junk.
4) Oil filled coil horizontal. Most like vertical. Epoxy filled don't care.
Weak condenser may kill the car, but not a coil
5) Too much dwell. The coil needs to be off to cool more than it is on. Think 50 % duty cycle.

[Craig Leach]

Hi Alan,
Is the distributor you are using a Bosch 009, 005 or 006? this is a rather common problem & most of the time I have dealt with this it is nothing
described. Very often it is the rotor. Bosch used a resistor in the rotor for radio suppression. If your rotor has what looks like epoxy between
the center contact & the terminal contact it can be burned & they will work for a little while & then fail. over & over. You will have spark to the
cap but not to the plugs when the issue rears it's ugly head. I have run across this on several peoples cars. There is a rotor for Porsche that doesn't
have the resistor but they are usually hard to find & rather expensive if you do find one. I carry a spare rotor, points, condenser & coil the same as others carry a spare roller, timer & coils. Give it a try & see. All of the fore mentioned items can be present @ the same time & contribute to the
issue.
Craig.

[Whitehair]

Allen,

I have had a very similar problem recently. I replace 3 sets of points coils and condensers in less than a month. One of our suppliers ask how the coil was mounted, when I bought my T the coil was laying on its side. He said if it was vertically mounted the electrolytic oil would have a better chance of insulating the internals.
I changed the mounting position about a month ago and the problem has gone away. I'm in my mid 70's, grew up around old tractors and can't remember ever seeing a coil mounted on its side. Well, it worked for me.

[Mark Gregush]

Are modern coils even still oil filled? I didn't think they still were. I have hung a few from the radiator support rod with no issues.

[jsaylor]

I made a bracket to mount the coil on the driver side off the water neck away from the heat.

[TRDxB2]

My 1926 Tudor has been modifies with a distributor and coil. I get anywhere from 5 to 1 mile and it stalls and will not statrt. No sparks. I have burnt 5 coils so far. What can cause the coil to die?

As you can see by the responses there are more questions and many questions.
When was the modification with the distributor & coil made? Had it run correctly before with the distributor set-uo & this problem just started to occur.
It would help to identify the what distributor & model you have. American Bosch, Atwater Kent, Texas-T, Bosch 009, Delco, other?
Is it connected to a 6 or 12 volt system.
Battery or alternator?
What coils have you been using as well. Most 6v coils usually don't require a ballast resistor but (internal or external) 12 volt coils usually do, but some have the internal.
How and where is the coil mounted.
How do you have everything wired (ignition switch, starter switch, coil, distributor, voltage source)

[big2bird]

Are modern coils even still oil filled? I didn't think they still were. I have hung a few from the radiator support rod with no issues.

Kettering coils are either oil filled, or epoxy filled.

[big2bird]

Any Kettering type ignition design uses 4 ampere primary current.

A 6 volt system require 1.5 ohms total
6 volts/ 1.5 ohms=4 ampere

A 12 volt system requires 3 ohms total.
12 volts/3 ohms=4 ampere.

This requires a 3 ohms coil, or a 1 ohms coil with a 2 ohms ballast resister. The ballast limits the let thru current to 4 amperes.

The condenser matches coil inductance in Milla Henry's.
That info is not published, so you have to observe point material transference to dial it in.

[big2bird]

Before it is asked, there is no such thing as a 9volt system.

The ballast register on a 12 volt system sees 12 volts.
The voltage drops to 9volts AFTER the coil sees 12volts.
This happens faster than your meter can see it.

It's purpose is current limiting to keep the coil cool, and prevent burning up the points.

[Norman Kling]

If you use the magneto and 4 coils with buzz points as Henry devised the T you will have less problems and the engine will run better with more power and speed because they run on AC and the faster the engine goes, the quicker the voltage raises enough to fire the coils. More cars on tours seem to break down with distributors or with alternators than those running as Henry designed them.
Having gotten that off my chest, now I will add something you can check. If you happen to turn on the ignition switch with at the position where the points are closed and leave the ignition on without immediately turning the starter or crank, you could burn the primary winding of the coil by overheating.
Norm

[Charlie B in N.J.]

Geez I love when someone posts an interesting problem then doesn't come back.