I've done the starter fluid trick on tires for years, works great.
Several years ago, I had a CJ5 Jeep. The original tank was mia, so I had a 5 gallon tank off of a small air compressor I welded some fittings into to use as a gas tank. Well, my stick welded bottom fitting had a pinhole in it and leaked. Didn't find it until after I had put gas in it, it didn't leak when I had tested it with water, I figure maybe a piece of slag chipped off or something. So, I needed to reweld it. This was way before the internet, I asked a few guys how best to do it, everybody said just drain the gas and fill it with water, so I did. I was welding away, took off my helmet to see a 2 foot high flame coming out of the filler neck! Scared the crap outta me! Even with the water in there, there were enough fumes to ignite. I was glad I had the cap off, or it might have been a bomb! I got away, let it burn out, then finished my welding with no problems....