90 GP Won't Start. HELP!!!

I have a '90 GP with the 3.1 and 190,000+ miles. I recently replaced the head gaskets due to some overheating issues. Once that was done, the car ran better than ever; for 2 days. While driving down the street, it simply shut off and coasted to a stop. Since then I have been unable to get the stupid thing running again. Working from a Pontiac shop manual, I have gone through all the troubleshooting steps ad naseum. During the course of this debacle, I have replaced the fuel pump (it was getting weak anyway), the DIS, and finally yesterday, the ECM. I am at a total loss at this point and am considering using a stick of dynamite to cure things once and for all. I have checked every single connection at least 10 times, I have spark at all plugs, and I have fuel pressure. The only outstanding issue I am aware of is that the injectors do not appear to be working as the plugs are dry after considerable cranking (which incidentally it does just fine). Again, I troubleshot the injector harness according to the manual and everything checks out as far as having power etc. in the proper sequence. All the fuses throughtout are OK and the fuel relay is new. I did NOT check the plugs for gas after replacing the ECM yesterday simpy because I was too disgusted to bother. My fear now is that I busted something internal, although I would think I'd hear something, and that would not prevent the injectors from working. I've been fighting this for over a month now and am presently reviewing local maps to identify the highest cliff in the area. Any ideas?!?!?

sounds like a classic bad crank sensor to me.

I replaced the crank sensor this past spring. I suppose it could have gone bad already.... That's actually something I spent a little time looking at yesterday to make sure it was connected and the wiring was all OK. Nothing lost by checking again I guess. Thanks for the suggestion.

A scan will reveal if the engine is seeing cranking rpms if so the sensor would not likely be the problem, do you have 12 v at the injectors, but no pulse? There is also a good procedure posted here for checking the cks, do a site search for crank sensor.

possibly a timing chain?

Thought I'd provide an update on this situation, it may help someone else down the road. After failing to make any progress, a kid I know that's in the local college Auto Tech program offered to have his Advanced Diagnostics class take a look at it. After towing it the 30+ miles up there, they discovered that the ECM ground circuit was pulling 120 ohms. Upon further investigation, they found that the ground wires "looked like a beaver had been chewing on them". They patched and soldered them up and the thing started right up. It runs like a charm again!