Fuel not getting to carb

I took the tank out of my 66 and couldn't get fuel to the carb, I put a gas can on and started the car so the pump was working. put the fuel line back on and primed the carb, the car started but wasn't getting fuel. Put the gas can back on and when I moved the car to where the nose pointing downhill fuel started siphoning out of the tank. Reconnected the fuel line and it started working fine.