Yup.
Like Curtis said....
I've tig welded cracks on aluminum diesel fuel tanks while still mounted on the truck.
They gotta be FULL !!!
It's the fumes that go bang! lol
Gasoline is far more treacherous.
On mc tanks I just flush em a couple times with the hose, then pop em with the torch before welding on the outside of the tank.
Pass the torch flame at the open cap now and again while doing the work.
All the gas is never gone, completely, so it's best to set it off before too much accumulates.
lol
It's actually a pretty good way to get larger push-in dents out of a tank.
Best to strap the tank, because a saddle type tank will spread out when it goes POP.
And ALL this is FAR from SAFE, should NOT be advised to those prone to injury or unable to accept periodic injuries of the working man... lol
NOT for the osha bunch!
Never ran the car exhaust into a tank, but that sounds like a great safety idea...
Dry ice?
Gosh, that's just not available in my little two horse town!
Y'all big city fellers got all the kool stuff!
Best
rc