I did check voltage at the coil, (12v ish, which I thought was high which lead me to the ballast resistor. But it wasn’t under load) and I pulled plug wires checking for spark after it died. Seemed fine.
Battery cables, not the things that they supply voltage to, but the positive and negative cables themselves. I went through a situation where my car engine would randomly start to decrease rpms at stop lights. I noticed a buzzing noise from the radio when it did that. I could blip the throttle and things would come back and no more issues until the next time it did that. I looked for things, even neutral safety switches as it would also not start after a short hot soak. Nothing I tried seemed to help that part of things. This went on for about a month! I finally went down to Radio Shack and spent $50.00 on a good volt-ohm meter.
One day, I drove home for lunch and the a/c didn't work, but it was a 10 minute drive. When I parked in front of the house, I left the engine running and got out the meter. While there, suddenly the fan relay kicked on as did the compressor, as they suddenly got voltage. With then not running, I measured a .5 volt loss between the battery and the engine block (or any other place I checked the voltage from the negative cable). After the blower relay clicked, the voltage loss was less than .1 volt. Both battery cables were OEM from when the car was new, so they looked just fine, but apparently the ground cable had an internal situation in it that could not be detected by looking at it. A new ground cable fixed it. In checking the voltages, they were always well within specs, or not nearly low enough to cause any issues.
After I put the old MP Electronic Ignition kit on my '67 Newport, I started it 4 times consecutively, but on the 5th try, nothing. Got the meter and checked voltage everywhere. Voltage was everywhere and in the right amounts. Al harness connections were clean and solid. Then I put a new solenoid on the next night. Same thing, voltage everywhere but no start.
Then I looked at the "good" battery terminal posts. I could barely see a bit of thin grunge on top, in the groove. They were "tight", so I tried to move them. No change. THEN I pulled one off and found a thin layer of grunge on them, between the cable end and post. More there than first suspected! So I got a wire brush tool and cleaned all contact surfaces and re-installed them. Had the same amount of voltage everywhere, BUT the car started and ran. Only thing I could think of, in this situation, was "volts" were getting through, but not "amps"?
These two situations, several years apart, proved to me that many of the "things" which might be in diagnostic trouble trees rarely cause problems. It's some of the things we normally figure "as good enough" that cause issues. In one case, a car just seemed to be "a bit off" in performance, so one of the things in the diagnostics was the ignition coil. After all, it was 30+ year old, so I got a new ACDelco coil for it. NO paint markings on the coil, other than a small, gold, ovaloid sticker on the bottom, "China". I installed it and no change, put the OEM coil back on and looked elsewhere.
For people who perceive they have to have the correct numbers in measurements? I once tried to set the dual points on a 440 6bbl factory distributor I had acquired, as a used unit. I put new points in it and adjusted the points with a feeler gauge. Wanting to get things exactly "right", I then got out my dial indicator for a completely precise adjustment. THAT's when I discovered that not all of the breaker cam lobes were the same height, which meant that each lobe had a different gap/dwell reading! YIKES!! The resulting dwell would vary PLUS depending upon which breaker cam lobe that "got lucky" enough to be used to do the settings. Which then can get down into coil saturation times and then into spark plug firings. Then consider that dwell affects ignition timing, degree for degree, and things can get worse, with not all cylinders firing at the exact optimum time as others might be. THAT was when I made the decision to get a Mopar Perf electronic ignition conversion kit for the car and not look back. UNTIL, of course, I might find a good source of new or refurb distributor breaker cams. Easier to find the electronic ignition kits that are good.
When the Mallory Uni-Lite system came out in the middle 1970s, that seemed to be the most exact-working unit at the time. Probably still is?
But with any of the electronic ignition kits ALSO comes the need for a good charging system. Each control box/mechanism has a minimum voltage requirement to fire the plugs. This can vary from about 10 volts down to 5.5 volts, depending upon the brand and performance orientation, it seems. In some extreme cases, the engine will turn over normally and "should start" otherwise, but with the addition of jumper cables from another running car, it fires off immediately (with the little bit of extra voltage, in this case, the car had a Chrysler Orange box on it, many years ago before knock-offs existed).
Gotta keep those volts and amps jumping to the correct places in the correct sequence and amounts for best results!
Just my experiences and observations,
CBODY67
