I'm trying to figure out why my car suddenly has no spark from the coil. I replaced the coil and still no spark. Also changed the ballast resistor and ignition control box and cleaned the engine ground wire. Still nothing. What else could cause this? Voltage regulator? The car has a Rev-N-Nator ignition on it.

Gahhhh....been awhile. 2013 to be exact. Off the top of my head

Do you have between 6 and 9 volts at coil +, key in "run"?

Do you have battery voltage at coil +, key in "start"?

Do you have battery voltage at the big usually blue ECU power wire, key in both start and run?

Does your pickup coil have continuity? Pull the plug and check resistance, if "0", it's gone open

Do the pickup coil wires show continuity/low resistance all the way to the ecu plug? If super high resistance, bad connection. If no resistance, wire or connector is broken/open circuit

Is the black wire with a yellow tracer between coil - and the ecu good? Should have next to nothing for resistance, but enough to notice...a few ohms.
If none, open circuit. If super high, bad connection.

Does the ecu case show continuity/low resistance to ground? ECU case must be grounded. If super high resistance is found, bad connection.

Rev-N-Nator? What am I missing?

Well OK. I learned something. I would assume diagnosis would be the same as OE stuff as outlined above. Check the ballast if there's one in the system. Simply jumpering the connectors to bypass it will do that. I would make sure that poking around with a test light won't damage anything like an MSD before doing so.

At some point, if voltage and resistance checks don't show a problem, you will have to throw something at it. We always had a spare known good distributor handy. Plug it into the 2 pin connector in place of the one in the engine, use some type of a spark tester on the coil wire, ignition on, spin the distributor by hand. Should fire the distributor. Same thing with a spare ECU.

Back in the old days, we carried that stuff in the car. Just to get home if needed.

pull the yellow wire off of the "ign" terminal on the starter relay to disable the starter. seperate the dist pickup zigzag 2 wire connector. Pull the coil secondary wire out of the dist & hold it 1/4 from a metal ground (such as the intake). have a helper hold the ign switch to "start". You drag the metal tip of the body half of the zigzag connector across the intake metal to make/break contact & see if the coil wire sparks. this takes the dist out of the picture so if it sparks the dist is the issue