Coils, coils, help me with my coil

[Chip M.]

I have a '64 FI TI roadster. Now that the FI problems are sorted out, I have electrical problems. I am on my third coil in as many months. The first (well, second since original) was purchased from Jack Podell as the "Correct" coil for my car. It went out and was very very hot to the touch. The second was an old coil from Jerry Bramlett that had the correct numbers and all but best of all... it worked.

It went out last week.

I have replaced the original TI amp with one from Dave Fiedler. He says if I blew the brain I would be the first in 16 years; so he has confidence in his product and I believe in him.

I replaced the harness from the TI unit (amp) to the coil and dist and I replaced the FI solenoid bypass wire. Both were from LL.

By the way NAPA has a direct replacement in their computer for the 1115207 coil which does NOT work!

Question is: what could be taking out my coil(s)?? Is it just fate? Stray electrons? The car has never been through San Francisco.

What do I check and how do I check it?

[Jack H.]

Re: Coils, coils, help me with my coil

Sounds like you're into a diagnose by component substitution mode... That can be a pricey and rather frustrating way to effect repairs!

The new silicone based TI amplifier boards are generally ROCK SOLID compared to the factory original germanium transistor based amplifiers. So, I tend to agree with what you were told in this area.

BUT, all the component substitution in the world won't fix a 'nest' problem... By that, I mean SOLID grounds at the TI systems' different connecting points.

I've seen Jeckyl & Hyde performance issues that were generated by: (1) poor grounding at the TI amplifier, (2) ignition switch integrity, and (3) chaffed wires at the distributor/coil.

Instead of simply swapping components, why not put science to work and go look/see what's happening? The output of the TI amplifier that drives the ignition coil's primary side should be a rather nicely shaped train of square wave voltage pulses (higher in amplitude during crank/start then during run).

An oscilloscope monitoring the coil's primary side should confirm/deny the ignition system is working properly up to the ignition coil. Don't have an oscilloscope or know how to connect/run one? Any auto electric shop or decent garage with an engine analyzer should be able to do the job in short order...

[Dan D.]

Re: Coils, coils, help me with my coil

One other symptom you don't want to ignore is you said the Jack Podell coil was very hot. You don't say the used coil was, but bottom line is the coil should not be that hot. Certinally it will be as hot as the engine is, but not anywhere near as hot as you say it was. If the coil is that hot, then there is too much current in the primary winding. You need to find out why. Also, if the second coil went out, then it too was probably hot. You need to measure some voltages and waveforms as Jack says. -Dan-

[Chip M.]

Re: Coils, coils, help me with my coil

Sounds like you're into a diagnose by component substitution mode... That can be a pricey and rather frustrating way to effect repairs!

The new silicone based TI amplifier boards are generally ROCK SOLID compared to the factory original germanium transistor based amplifiers. So, I tend to agree with what you were told in this area.

BUT, all the component substitution in the world won't fix a 'nest' problem... By that, I mean SOLID grounds at the TI systems' different connecting points.

I've seen Jeckyl & Hyde performance issues that were generated by: (1) poor grounding at the TI amplifier, (2) ignition switch integrity, and (3) chaffed wires at the distributor/coil.

Instead of simply swapping components, why not put science to work and go look/see what's happening? The output of the TI amplifier that drives the ignition coil's primary side should be a rather nicely shaped train of square wave voltage pulses (higher in amplitude during crank/start then during run).

An oscilloscope monitoring the coil's primary side should confirm/deny the ignition system is working properly up to the ignition coil. Don't have an oscilloscope or know how to connect/run one? Any auto electric shop or decent garage with an engine analyzer should be able to do the job in short order...

Thanks Jack. I will hook up the scope and see what we get. I am at the point now where I need to start from the battery and trace current all the way to the explosion in the cylinder. Something is rotten in Denmark with this system and I hate electrical problems, Especially transient ones.

[Ken A.]

Re: Coils, coils, help me with my coil

I would say you still have a coil problem as the first was probably a bad coil and the second a used coil on it's last leg. Also, don't be offended, is the coil hooked up correctly? I seen mechanics swear that "it won't run hooked up like that".

[Chip M.]

Re: Coils, coils, help me with my coil

I would say you still have a coil problem as the first was probably a bad coil and the second a used coil on it's last leg. Also, don't be offended, is the coil hooked up correctly? I seen mechanics swear that "it won't run hooked up like that".

Thanks Ken. It seemed so backward to hook up the positive to the black and negative to the white that I triple checked it. That's the way the wiring diagram showed and the way the old one was wired.

[Wayne M.]

Re: Coils, coils, help me with my coil

... It seemed so backward to hook up the positive to the black and negative to the white that I triple checked it. That's the way the wiring diagram showed and the way the old one was wired.

And that is the correct hookup with a '64 or '65 TI harness -- it does sound counter-intuitive. In 1966+ they switched the in-line resistance (white wire) , to the positive side of the coil "for added protection of the ignition pulse amplifier in case of accidentally grounding the ignition coil wire". [from Nov '65 Chev Service News].

But looking at the difference in the two K66 circuit diagrams ('64-5 vs. 66+) it shouldn't make any difference from the perspective of the coil, IMO.

[Wayne P.]

Re: Coils, coils, help me with my coil

Just a question. Does the balast resistor have anything to do with coil performance. ( sorry if this is a novice question )

[Loren L.]

Re: Coils, coils, help me with my coil

No ballast resistor.
Chip, is this the same CV that I remember judging at Pismo Beach in 1985?
Silver? Large "X" in the engine stamp?
Why can't I remember what I did last week?

[Ken A.]

Re: Coils, coils, help me with my coil

Just a question. Does the balast resistor have anything to do with coil performance. ( sorry if this is a novice question )

There is no ceramic ballast resistor used with TI, however the white cloth wrapped wire is the resistor(about 6 feet long) and does affect coil longevity.

[Jack H.]

Re: Coils, coils, help me with my coil

Yep, no ballast resistor with a TI setup.

But, there IS another potential for error and that lies with the radio RF capacitor that was installed on the coil when a given car (most) were equipped with AM/FM radio option. While this is somewhat unusual, it's possible for the radio capacitor to have a skinned lead wire that's shorting out the ignition coil primary OR the capacitor to have SO MUCH internal leakage that's it's essentially presenting a short circuit path to ground at the coil primary.

Competent techs who troubleshoot ignition system 'funnies' always start by disconnecting the radio RF capacitor (let it's lead wire 'float') before they begin probing the ignition circuit...

[Wayne M.]

Re: Coils, coils, help me with my coil

....But, there IS another potential for error and that lies with the radio RF capacitor that was installed on the coil when a given car (most) were equipped with AM/FM radio option .... internal leakage that's it's essentially presenting a short circuit path to ground at the coil primary ......

Good point ... except that K66 C2's didn't have a radio capacitor on the coil +ve terminal from the factory. Nevertheless, Chip should confirm.