91 3.4 starting problems

i have a 1991 grand prix with a 3.4 duel over head cam. the car cranks over strong, has spark on all cylinders, and proper fuel presser on the fuel rail but will not fire. i have been able to get it started twice after it was sitting for a bit since it started acting up and it ran perfect with no problems of bogging or killing, but now it has been sitting a week without starting and now im starting to give up on it. i have read about problems with the crankshaft sensor but i been having trouble trying to locate it can anyone help me with this problem or tell me if im on the right track.

I would look at the crank sensor and the ECM. The 90-93 GP's had high failure rates on their ECM's (especially service number 1227727) due to it being mounted under the hood. If you get the car started again, try tapping on the ECM (it's located in the passenger fender well below the black plastic cover) with the engine running. If the car stumbes or quits, you found your problem. The crank sensor is located in the back of the block, just above the oil pan rail, and slightly toward the passenger side of the engine. It is held in the block by one 8mm headed bolt, and has a 2-wire harness (purple and yellow colored wires I believe)