Only thing I’ve ever seen patch a gas tank on a car, is Seals All. I used it on my 66 Chrysler, and my current 65,10 yrs ago, still holding, both times, rusted at the half way seam. A plug of some sort,on a diesel tank and a sheet metal patch using the Seals All should work. It’s cheap, goop type stuff, sold at any hardware store. I keep it in the tool box. Good for radiator tanks, plastic oil pans. ”Seals All” in the yellow tube, with a Farmer on a Tractor. It works.
I was at a Flying J truck stop working on my truck about a month ago and I accidentally broke a plastic coolant hose. I was stuck for several minutes holding the hose and trying to think how to get out of this. I used my mechanic gloves to hold it in place while I quickly took out 3 buckets that I keep inside my truck. All in all, I think I spilled about 3 gallons, but it felt like it was more than that. It stressed me out good thinking that if someone noticed, then Flying J could charge me for environmental cleanup. I got lucky.