91 firebird help

I have a 1991 3.1 v6 pontiac firebird. I have replaced starter, distributor cap, coils, spark plugs, icm and just recently all injectors. First thing in the morning the car starts right up with no problem and stays on and runs great. Then the second I turn the key off and try again to start the vehicle it will not start at all. It does this everyday. What could be causing this issue? I am not a mechanic this Is a project I have recently gotten. The car has been sitting in a yard for a long time. Any help or suggestions would be appreciated!