rebuilt my carb.. now i need some troubleshooting help.

no, i did not screw it up. the carb works. its a 2 barrel carter, stock piece for my 318. the reason i rebuilt it is because the car would run just fine, then it would kind of die back a little, sputter, and die, then be almost impossible to restart. took a long time to get started usually anyway, died frequently.. etc. now i rebuilt the carb, easy, cleaned it out thoroughly, reinstalled it. now i have to pump it a few times to get the car started, or, it will fire right up immediately. either way, it wont run for more than 30 seconds or a minute, and it dies, no warning, just stops dead in its tracks. i have suspected my fuel pump for a little while now, but i dont want to go buying parts if i dont need to. any ideas?
..plz.
-jeff