Not knowing what sort of vehicle we are dealing with, here are a couple theories:
Theory 1: Debris clogging path from tank to pump. Something got jarred loose when you pulled tank.
Test/ Remedy: Disconnect line at inlet side of fuel pump. Connect a section of hose there and place in a gas can. Try to start/run vehicle. If it runs properly, problem is upstream. Proceed to finding/ blowing out clog.
Theory 2: Something changed in the way the tank was venting when you removed and reinstalled.
Test/ Remedy: Remove gas cap and try to start.
