My '90 Grand Prix with the non-turbo 3.1L V6 will not start but will turn over. We have changed the fuel pump and filter along with the manifold pressure sensor and it still won't start. It will almost turn over after it sits for a bit but dies immediatly. This is very puzzling and would appricate any suggestions anyone might have. Thanks.

check fuel injector wiring harnes for bare wires.also check for shorted injector

make sure you have spark, and check the gaps as well

My '90 Grand Prix 3.1L V6 has same problem, check spark in the 6 cylinder. if no spark, it's your ignition control modual. im also a mechanic that has done 5 of these over the last year