Spark to coil, not to plugs Ford 8n Side Mount Dist.

Hello All,

I have been reading everything I can that is related to this problem and am out of ideas, kinda. Let me explain.

So racking my brain a bit...after getting through a bunch of wiring issues and getting spark, seems I am not able to get spark across the rotor out the cap and down the wires.

I turn the key on and crank, no spark at the end of the plug wires. I hook a plug tester to the wire and nothing shows. I used an old plug gapped out a bit at the end of the plug wires and no spark.
I pull the coil wire from the cap and hook to either a plug tester or old plug and get lots of spark. Opening up the cap and rotor look ok. The metal clip is on the shaft of the dist. under the rotor. I did not install the cap and rotor but they are new.

Question - is there a different cap and rotor for the original dist.? This looks original and cap and rotor are new. Is it possible the last guy got the wrong cap and rotor? I did order some replacement wires but they are the copper type which I believe are no good with an electronic ignition, and they do not change the outcome when installed, no spark.

Current configuration:

This is a 12V converted 8n with side mount distributor. I am running the petronix ignition module.

Currently wired, as far as I can tell, per the wiring diagrams I am finding from google. Positive 12V, hot with key, to positive of coil. The coil is a NAPA 4.0 ohm primary resistance. Petronix is wired black to negative of coil, red to positive. I also replaced the starter solenoid to a 4 post that I found recommended on another forum. I have +12 in, starter on the other side. Pushbutton starter switch to ign. post and other small post is jumped. That all seems to work fine.

The wires that are on it are spiral wound, not copper.

Thank you very much!

Take your dist. cap off, hold a gap from your coil wire to your rotor and see if it arcs. If it does, you have a shorted rotor. Also look for hairline cracks in your dist. cap, or look for carbon tracing. In the past, as a practical joke, I have taken a lead pencil and drawn a line inside a dist. cap, rerouting spark to ground.

(quoted from post at 18:47:53 07/18/21) Take your dist. cap off, hold a gap from your coil wire to your rotor and see if it arcs. If it does, you have a shorted rotor. Also look for hairline cracks in your dist. cap, or look for carbon tracing. In the past, as a practical joke, I have taken a lead pencil and drawn a line inside a dist. cap, rerouting spark to ground.

Click to expand...

hat is about as bad as saran wrap across the toilet bowl! :twisted:

I'm basing this on previous posts on the subject, and a very weak memory!

But as I recall there was a way to not get the trigger ring on the distributor shaft properly, or something along those lines.

Doing so caused the coil to fire between the cap terminals.

If you can't see what's happening with the trigger, and it appears the fire is between the terminals, give Pertronix a call, they are very helpful.

Also be aware aftermarket caps and rotors are notorious for being improperly made or boxed. If you have an old cap and rotor, compare them closely.

You can use the solid wires with a standard coil. If you bought the super flame thrower, for some reason they recommend resistor wires, specifically spiral core resistor wires, something else to discuss with Pertronix customer service.

(quoted from post at 15:47:53 07/18/21) Take your dist. cap off, hold a gap from your coil wire to your rotor and see if it arcs. If it does, you have a shorted rotor. Also look for hairline cracks in your dist. cap, or look for carbon tracing. In the past, as a practical joke, I have taken a lead pencil and drawn a line inside a dist. cap, rerouting spark to ground.

Click to expand...

Think that narrowed it down... Removing the cap and taking the coil wire from the cap and holding to top of rotor I get no spark (guess makes sense because the spark has no where to go?). Holding to the center of cap same result. Holding coil wire to point in cap that goes to a plug wire and I get a healthy spark.

I will order cap and rotor and see what the outcome is.

Thank you very much for the insight!

It may well be that you cap or rotor are somehow causing this issue, on the other hand it's possible that somehow parts have become mixed and unmatched and your junquetronics "module" is "firing" the coil when the tip of the rotor is between high-tension terminals in the distributor cap. Have seen that a number of times.

Doesn't work well.

Make sure that the rotor spring or contact is making contact with the button on the top center of the distributor cap. Measure the distance from the center of the rotor to its outside edge and make sure it is wide enough to pass over the outlying terminals on the distributor. Often the terminals will have L-shaped cut out so the rotor arm comes close to the teminals at both the side and vertical gap.

I ran into exactly this problem with a friends late 60s Barracuda. The replacement rotor or cap was not high enough to touch the button on the cap or the rotor arm was not long enough or high enough to come into close proximity to the cap outer contacts. What many people don't realize is that the spark generated by the coil has to jump a very short gap between the rotor arm and the cap terminals.

I just read that the rotor clearance between the arm and the terminals should be between 0.10 to 0.035 inch. I would double check this.

I made a mistake in my previous reply. The recommended gap between rotor and terminals should be 0.010 to 0.035 inch and not 0.10 inch. That is too great of a gap. My bad.