[Rob Doe]

Fuel or spark. That's the big question. I had a run and die issue a couple months ago. I too had a freshly rebuilt engine. But the car was new to me and it had several issues that I ran into before it was reliable again.

My car turned out to be wired incorrectly for the model A. The ignition switch was wired into the circuit before the coil instead of after the coil. (Between the coil and the points) This prevents you as the driver/mechanic from receiving the correct voltage when following the known trouble shooting voltage tests at the primary terminals of the coil.

I watch to see if the ammeter is flickering from negative to positive when attempting to start the car. (switch on, of course) If you see the flicker then your ignition circuit is at that moment good all the way to the points.

So, assuming you see the flicker when you start the car and it does start; I would immediately try to restart the car when it fails and watch for the flickering ammeter. No flicker no primary ignition circuit, therefore no spark.