Pontiac Repair: 1988 Grand Prix, mass air flow, crank sensor

Question
We just put a good used 3.1 motor in it and it won't start.  We've replaced the coil pack, crank sensor, computer mass air flow map, snap on code reader pulled no codes.  Has good fuel pressure, has spark.  Don't know what to try next.

Answer
Hi Mike:

Well you need three things for the engine to run. spark,fuel and compression. I doubt you have a compression problem you siad it was a good engine. You said you replaced the coils and crank sensor so I assume you have spark now on all 6 cylinders? last is fule you have fuel pressure but how about injector pulse? that is the signal to run the injectors to dump the fule into the engine. Unplug 1 injector on eash side of the engine and get a tool called a noid light and plug it into the injector connector and crank the engine that light should flash. if it doesn't then you have to find out why? if you replaced the computer did you switch over the prom inside the computer? A bad ground wire or one that was not connected. That car had a 2.8 liter in it from the factory did you switch over all the electronics and the harnesses from the 2.8 to this engine?  just a few things to look for/at. Good luck :}