replaced voltage regulator, now no spark

[VitoV]

Hello all,

I have a '66 that's my daily driver while we're in driving season down here in Texas. (Sunny and 74 degrees at the moment...)

Motoring home last night, I noticed at one point that the instrument lights were unusually bright. I started to think, gee, why are those guys on Pelican always making such a big deal about how dim the lights are, when obviously you just have to let your eyes adjust and... then I noticed that the volt meter was pegged high. Whoops!

I dipped the clutch and gave a blip of throttle, and voltage dropped down to the 12V range. It was alright for the remaining few blocks to the house. The incident was a matter of seconds, I'm sure.

Today, I replaced the (original?) mechanical voltage regulator with a modern solid-state item, thinking how pleased I was that this problem was such an easy fix and I wouldn't miss a single day of pleasant weather.

But now I find that I have no spark! Getting fuel at the carbs, starter turns over fine, and the remaining electrical systems seem to be working normally. Swapping the original VR back in and trying again made no difference.

My ignition system has a Pertronix module and a Delta Mk Ten (I think) aftermarket CDI.

It seems to me unlikely that something would have burned out during the voltage excursion, particularly since the car ran without any symptoms of trouble after the volts had returned to normal levels. So why won't it start now?

Before I start going through the ignition components and connections-- wasting precious winter driving weather!-- I thought I would ask the board if anyone out there had a similar experience, and if so what your solution was. Am I missing something obvious? Thanks in advance for any light (or sparks) shed.

Vito

[Neel]

Vito,
Voltage spikes do nasy things to electronics.. First, double check that you didn't knock a connection loose during the new V/R install, it happens to the best of us.. Second, you may have fried a circuit in the CDI unit or the Pertonix unit..

[VitoV]

Thanks Neel. I can certainly see how a voltage spike could ruin electronics, though as I said I would expect that kind of failure to manifest itself more or less instantly.

Pertronix does have a handy test procedure for their units-- fyi to others reading this thread-- and if it gets down to that I will try it. Testing the CDI might just mean bridging it out of the circuit and checking for a result at the spark plug.

[VitoV]

Well, this turned out to be educational! Once I got a chance this evening to sit down and do some serious Googling, an answer popped up from an obscure corner of the Web. I hope you guys don't mind one of those annoying threads where the OP answers his own question at the end...

The voltage regulator: I am probably the last person in the world who was using a mechanical VR on a 911, but wow what a difference with the solid-state unit! I think my "if it ain't broke" philosophy let me down on this one-- if I'd known how much better the modern VRs were, I would've swapped in that new one I had on the shelf a long time ago. And, not surprisingly, the VR was not the source of my starting problem...

The Pertronix: Internet scuttlebutt suggests that these units can handle overvoltage situations fairly well. My experience shows that this is true to at least some degree, as my brief voltage frolic did not cause a failure. The Petronix was not the source of my starting problem...

The CDI unit: Now this is interesting. I thought this aftermarket CDI was just another odd "gift" from the PO, like the top-of-the-line tape deck.* But it turns out that the Delta Mark Ten-- there were no Marks One through Nine that I could find-- is actually kind of a cool piece of vintage speed equipment. And, more to the point, it is a somewhat quirky piece of speed equipment. It seems that it is something of a small miracle that mine was still operating after probably 40 years, because certain internal parts are known to degrade and cause strange operating behavior and, finally, total failure.

Which is what happened to my unit. So why didn't it happen immediately during or after the voltage spike? I think it's down to the peculiar characteristics of some rather primitive internal capacitors. An analogy might be how you can wrench your back and feel pretty much ok afterwards, but the next day you can hardly get out of bed. Not to get technical.

But here's the good news: it turns out that I actually have a Delta Mark Ten B. The B is significant, because it means that, tucked away out of sight, there is a handy-dandy Bypass switch. So, one press of a button, and my '66 was rarin' to go once again!

At some point, I'm going to take the CDI out and see if I can renovate it with some modern components. It's kind of a neat old thing, and at least theoretically it can serve a purpose. But I think I'll wait a while before I start digging into the wiring... did I mention that it was 74 degrees and sunny today?

Thanks all,
Vito

*the pristine, high-end tape deck is especially weird in this car because it wasn't installed until sometime early last decade. Where did he find a brand new tape deck in 2004?