Stick a straw in a glass of water, put your finger over the end, then pull the straw out and suck on the other end. You can't get the water out unless you remove your finger from the other end. The engine would not get the fuel in the line due to the clunk sucking up against the tank, this stops the flow. It's easy to try, and won't cost anything. You would not get the same effect in a tight turn as the clunk falls down the side of the tank, where there is more room.