In an effort to fool Darwin, I've repaired a lot of vintage fuel tanks, mostly on military vehicles......if you file that glob of solder down, locate the pinhole, tin a penny or a strip of flattened brass cartridge case with 60/40 acid core, and put the penny/strip over the hole or seam and then apply the heat with an old school soldering iron, no open flame, you will get a good strong job. Last thing you want is a pressurized tank of fuel splitting open just before breakfast. Silver solder, you're looking at 700 deg's...plain ol' 60/40 at 450 or so.
