Yeah, I would say a tank or a plumbing problem for sure. Even a tiny air leak in a fitting will prevent the pump in the carb from pumping. I use either Tygon or Hayes rubber fuel lines, fuel barbs at every connection, and wrap the connections with wire to secure them.

The carb is fine if it will draw fuel from another source as you say. Your problem is in the tank or the plumbing.

AV8TOR