1989 Chevrolet Corsica won't start

I have a 1989 Chevrolet Corsica Hatchback, V6 2.8 motor. The car originally, when I got it, would start right away, very strongly. After driving for a half hour or so, and you shut it off and let it sit for 15 minutes or so, the car would not start back up. It would crank and fire, but quit running after 3 seconds. Waiting an hour for the engine to fully cool down would fix it, and the car would start and be able to be driven. After a month or so, the car eventually stopped running completely. One or two cylinders quit firing, but the car has spark. We tried to get it to fire with Ether (starting fluid), it would run on the starting fluid, then quit. We replaced the fuel pump, and it didn't fix it. Have yet to replace the Fuel filter and air filter. If the fuel filter doesn't fix the issue of the car starting, what else could it be? I have no idea, and I seriously need help.