1992 cadillac won't start

My 1992 cadillac deville wont start at all I took my battery and alternator to napa and they said they checked out fine. I stuck a screwdriver in the spark plug wire and their was power to it. I can smell gas coming out of the exhaust. It used to turn but wouldnt start. Now I stick the key in the ignition and the motor doesnt turn at all. The lights come up on the radio and everything else. Last year I bought a new engine control computer unit and kept the same prom chip. I dont know if their is something wrong with that or not. Also someone hit the rear end in a walmart parking lot. they hit it on the left side and pushed the bumper light sideways and they broke the left rear panel.