Hopefully this helps someone in the future. If anyone has questions just let me know. My car developed a wicked raw gas smell. Any time a window or the sunroof was opened beyond a crack it was awful. A lot of searching revealed a think crack in my coupe's fuel filler neck right where it exits the tank itself. I've put a few pictures here to give a decent view. The red arrows point to the crack but isn't really seen in the photo. The leak found, the next problem was how to repair it. The fuel tank is made of polyethylene which has one massive inherent problem. Almost nothing except polyethylene itself will stick to it! My first thought was to rough the area up with sandpaper and pour some melted polyethylene onto the crack and surrounding area. But that would mean draining and flushing the tank and that means removing it. Right now I can't afford the cost of removing the tank and if I did remove it, I would just replace it. A call to 3M revealed a product called DP8005. It's one of the only epoxies that will adhere to polyethylene. It's actually a structural adhesive. Finding a place that will sell individual tubes wasn't easy but in the end you have to buy the DP8005 in a 35ml 2 part cartridge, a gun to use the cartridge, a 10:1 plunger and a mixing nozzle. I had to buy a 12 pack of the nozzles. Total was about $160
According to 3M no prep of the area beyond removing grease and dirt is necessary and the 2 part epoxy has a 3 minutes time frame for use once mixed. Since the plastic was cracked, the first think I did was use a sharp point to make relief holes at either end of the crack. I used a test light probe. I scuffed the area with sandpaper (even though the instructions didn't say it was necessary) and cleaned it with brake cleaner. The instructions were simple. The mixture swirls around in the mixing nozzle and came out a bit more liquid than I had hoped. I went around the entire base of the filler neck slowly. I tried to be careful not to get any on the body of the neck where I would have to replace the filler rubber flex hose. Full curing time is 24 hours.
Once cured, the adhesive had a sort of micro bubble appearance. My fear was that while it might be a strong bond, it might not be air tight and still allow gas vapor to escape. The greatest surprise was when I removed the mixing nozzle and fitted a new one. It STILL worked! The seal from the nozzle to the cartridge was so good that the epoxy parts in the cartridge didn't dry out! So, I made a second pass over the first application. The next day I was able to do the same thing making a total of 3 applications. And to think I was angry at having to buy 12 nozzles!!!
Well it's been 3 days since the 3rd application fully cured and knock on wood it's sealed and no gas smell even with both windows wide open. As an aside, I have also decided that to keep the old hoses and anything further happening to the tank, I'm making it a habit of cracking open the fuel filler cap after each decent drive of 50 miles of more to relieve the strong vacuum created in the system. I think that going from full down to a quarter of a tank puts a tremendous vacuum strain on these parts that have been doing their job since 1995 on my car.
Pic 1 shows the filler hose still attached and I'm pointing to the crack
Pic 2 has poorly drawn red arrows shwoing the length of the crack, about 1.5". The hose is removed and I have painters tape over the opening.
Pic 3 shows the finished seal after 3 applications from the single 35ml cartridge.
Hope this helps.