When I put the Mopar Perf electronic ignition conversion kit on one of my cars, things went fine. I started it five times, but the sixth time, it did nothing. Checked all connections with the volt-ohm-meter and everything had plenty of volts. The battery terminals looked clean, but there was a thin layer of grunze in there. Cleaned it out and thing worked reliably ever since.
On another car, it had a problem that was internal to the ground cable. When it didn't work right, about .5 volt would be lost in the mix regardless of where I checked battery voltage under the hood. When things were working ok, no voltage loss. That one took a good while to track down!