What happens when you try to pump the gas? Does the pump handle keep clicking off?
The neck quickly fills up with gas and the pump shuts off.

I wonder what would happen if you poured a small amount in the filler neck, like 8 ounces from a bottle. Would it drain passed the check valve?
Once the neck fills up, there is some kind of bypass to allow the gas to drain from the neck. I suspect it's around the gas float shutoff.

As for ignorance, we are all in the dark with obscure issues like this. The purpose of this forum is to learn and keep these cars on the road.

I took some pictures last night. I use my cheap endoscope to take a look see down the gas filler neck.

Once the camera is down the neck, this is first adventure. I have no idea of what this could be. I suspect it's to get the flow of the gas straight or support for the neck.

First Obstacle

Once you get past that then you find the second obstacle which is the fuel filler tube check valve.


Second Obstacle


The last item must be the fuel tank overfill check valve.

The third and last Obstacle

I suspect it's closed and not allowing gas to flow by. I might want to take some more pictures again once I get the gas out of the car.