You can't really repair a leaking fuel tank - metal ones can be welded but this is more trouble than it's worth as you have to remove it, drain all the petrol, wash it out with water, ensure all the petrol fumes have dispersed etc. Far easier and safer to get a new one. I'm surprised than Puntos have a metal tank though - I'd have thought that it'd be plastic as it's a fairly modern design.
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Fart In A Tin
<font color="orange">1994 Punto 55SX, metallic red, small, Italian and beautiful! </font id="orange">