Any tricks for finding a leak in fuel line ?

AAndrews said
I would think that if the tank is the original and you are using an original pick-up, this shouldn't happen as it would have been a problem since the car was new. If you can, take the sending unit back out and plug the input end of the pick up tube . Submerge the unit in a bucket of water and blow air through the output end of the tube . If there is a leak, you should see bubbles in the water.
I'm thinking it may be leaking where the tube going into the tank is soldered to the piece that holds the sending unit to the tank.

Thanks Ill give that a try , but it is not the original tank and also one more thing: if that piece is not soldered correctly how would that make the pickup tube leak? If the tube is one solid piece and is just held in place by that connection why would the tube itself leak ? Maybe I’m misunderstanding you. Thanks