I have 1991 RS Camaro TBI with 305 V8. Car has been starting up and driving good until yesterday. Now it only wants to crank but not start. Every once in a while it will start up but idle rough and cut back off. I don't know what the issue is. Last night I totally tore down and rebuilt the TBI and this morning it started right up and ran strong. Now it is back to doing the same thing again. Anybody know of anything i can do or any know issues. Thanks

 

Have you confirmed that it's a fuel issue? When it's not in the mood to run, put some gas or starting fluid in the throttle housing and see if that allows it to run until exhausted.
Check the fuel pressure, make sure you check it when it's not running properly just in case it's not being consistent.

Are both of the injectors working?

I don't have personal experience with the 305, but I'm assuming it's set up similarly to other 1980s GMs I've worked on. When you first turn on the key to "run", the fuel pump should run for a couple seconds. After that, if you blip the starter for just a moment (not long enough to start), it should again start running the fuel pump for a couple seconds. This should be reflected on a fuel pressure gauge if you hook one up.
If the fuel pump doesn't run from blipping the starter, then the ECM might not be seeing reference pulses from the distributor. Since your car sometimes starts, this problem might not be happening consistently.
If you crank the starter long enough, eventually the fuel pump will come on anyway because of the oil pressure switch, but if everything is working correctly the pump should come on just from seeing distributor reference pulses.