Briggs & Stratton year: 1999 model: Quantum 6 hp. Wont start?

I have a push mower with the above engine. A couple of years ago it quit working and as I had another mower available I didn't bother to fix it. Now I have a John Deere 6.75 hp B&S that works like a top. Anyway, recently decided to try to fix my old mower. I got it working for a while, but then it wouldn't start. Now I have found that the reason it won't start is that it doesn't get any gas. Every time I press the primer on all that I hear is air, not the sound of gas getting pumped. There is nothing that keeps gas from getting from the tank to the engine. I have put a new fuel line on, so there isn't any problems with that. The air filter is the original so that is a possibility. There is a paper piece that goes between the piece that holds the air filter and the carburetor that since it is gone could also be a problem. Also the problem could be the carburetor it's self. I have used a engine start fluid bottle and have poured gas in the engine and started it, but obviously it only runs for a few seconds. Any help would be greatly appreciated.