How big are the holes?
If it's not crazy bad maybe you can use JB weld that can be used in gas tanks.
I hope this helps.

 

It's big enough that I can get my hand through it. I'd say a good 3rd of it is gone. I'll try to get pictures tomorrow.

 

Is it just the sheet metal around the filler neck or is it the filler neck?

I noticed on my 99 that it was rusting through just below the filler neck. I treated snd painted it. I took out the rear speakers and found lots of rust inside the cavity there. I treated that too. I think the filler neck is probably a separate piece that sits inside that body metal. I guess I could look up a parts diagram from the manual but no need since it’s intact.

 

It's just the steel around the neck. But it's completely rotted through. I'd need to cut out a good chunk to stop the rust. I was hoping that there might be something like a drop in piece I could patch into it or rivet in place instead of attempting fiberglass or welding around a gas pipe. But the only things I've found that are along those lines are for jeeps and fords. I was thinking I might be able to modify a Ford one to drop in after cutting out the rot.

 

Same issue on a 2004 EX we just purchased for our son. I’m wondering is someone could 3D print something out of plastic to rivet to the remaining scraps.

 

If the fill adapter is rotten, how is the rest of the car,floor ,rocker pannels frame where the trailing arm bolts to?

 

Ours goes on the lift for the alignment hopefully this week so we will know more but from what I can see from my creeper is the inner rockers have some rot nearer the rear and the gas tank skid as well around the edges. We have a 1994 Toyota pickup and a 2004 F250 so rust doesn’t scare us too bad. Ha. I can stick stuff together with a welder but it might not look pretty when I’m done. I’m a better grinder than a welder but I have some talented friends. lol