Personally I would persist with the welding - or put the sealant on the outside. It only takes a small bit of sealant to black the pump. The garage down the road from me got a really nice wedge TVR cheap becuase it ran roughly. Previous owner had spent £800 at a TVR specialist trying to get it fixed but gave up. New owner decided to fit a new fuel pump. On taking the old one out of the tank he found it had been fitted with copious amounts of sealant - which had squeezed into the tank and blocked the fuel line. Tank clean out and blow through the fuel lines and runs like a dream now - even made the Le Mans classics and back in one piece - impressive for a TVR
