1991 Toyota corolla sometimes it starts and sometimes it won't but when it does start the car will run for a while then stop and I have to wait for a half hour for it to turn back on or somtimes I even have to jumpstart it, I already changed the water pump the ignition coil the battery the gas pump and nothing helps what else might be the problem.

When the fault occurs you need to check the spark and also the fuel settings so as to confirm the area of fault. If there is no spark check for the TRIGGER pulses to the HT coil. If absent check on the ignition system.
Also check on the fuel pressure /fuel settings , if there is overflow or no flow of the fuel from the pump specially when it is heated up..