Electrical Failure. Engine Dies. Won't Start

[Glow Worm]

I get in my car...start it....let it idle for awhile...back it out of the garage...put it into Drive, and the engine dies.  I put it back into park, and it will not start.  Everything is dead.  No clock, no dome light, no radio, no ignition.
Once, I replaced the ECU/ECM, and voltage regulator and it started up.   Another time I just replaced the ECM/ECU and it started.
The parts I used were parts that were previously on the car.
A couple of times I was on my way to my sons house and it died in the middle of the road.  I didn't have any tools or parts with me so I wiggled a few wires, and checked connections, and in about 10 minutes it started up again and I drove the car home....about 80 miles, with no issues.
For weeks the car will start and run just fine every time I get in it, but then, out of the blue this power robbing Gremlin shows up.
I have replace the ECU/ECM, voltage regulator, and ballast resistor.
Any suggestions?

[Brads70]

Check the big red wire going thru the bulkhead It's commonly corroded and then a poor connection/burn. Or maybe do the ammeter bypass to eliminate that as an issue.

[Rich G.]

FYI the ECU , distributor and voltage reg. Have nothing to do with you losing all power. You can remove them and you would still have lights and power to crank the car. Ck the main power wire like Brad said. Try pulling on wires when it runs to see what shuts it off too.

[YellowThumper]

I also agree with above noted issue with red wire at firewall connection. They fail.... badly.
Simplest method is to add additional heavier power wire from alternator to (IIRC) starter solenoid. This effectively renders the amp guage worthless as it provides access for charge power to bypass weak point. If while car is running you could use an infrared temp tester and check that point compared to something adjacent to it. If it is original it is failing...
Been there and have bypassed mine. If blades are corroded. It is not from weather it is the heat.

[Dakota]

Check the big red wire going thru the bulkhead It's commonly corroded and then a poor connection/burn. Or maybe do the ammeter bypass to eliminate that as an issue.

   The picture below shows what my bulkhead connector looked like when I pulled it apart (the burned out one is where the big red wire goes through) after having similar "now she runs/now she don't issues" that you described.  Just about every bit of juice that goes anywhere in the car goes through this terminal, so a bad connection can easily impact everything you listed.   The ammeter bypass that's mentioned is a good way to reduce the load on the connection.  Adding relays for headlights will also help.   There are lots of people here who can help you could down this road if you want to.

[dodj]

Check bulkhead connections, fusible link connector, ammeter connections. At least one is probably corroded/bad.
Also check your block and body ground wires.