After a week of trial and error, trying to follow instructions from members, especially jfb, I gave up trying to start the car (see the following thread)
http://forums.corvetteforum.com/zerothread?id=845521

So I loaded the 91 on a trailer early this morning and took it to J&D Corvette. I've dealt with Noe Garcia and crew for a number of years and have always trusted them. (more so than any dealer I've dealt with)
A couple of hours later, they called and told me the problem is the VATS. Somehow, the tumbler has gone south and they need to install a new tumbler and get some matching keys. Including diagnoses, parts and installation $270.00. I won't get the car back until Tuesday and I am still reserving some room for something else to be wrong, but here's hoping. If there's additional problems, I'll post them here.
My hope is that, in this case, my fix will keep someone else from going through a week questions.
I guess the lesson to be learned is: you MIGHT be able to crank the car over and not start it when the VATS takes over.
Thanks to all the members for their input, suggestions and help.

 

I'd like to understand this better because it doesn't make sense to me. VATS measures the resistance of the pellet in the tumbler and if it is within tolerance, VATS closes the start enable relay which will allow current to flow to the starter solenoid when you advance the ign sw to, "crank". And it also sends a signal to the ECM to exercise the fuel injectors. How the ign tumbler can allow VATS to close the start enable relay but not send the FI enable signal to the ECM doesn't make sense to me. I can understand a bad VATS module, but not a defective ign tumbler with these symptoms.

 

When I pick up the car on Tuesday, I'll try to talk to the tech to glean more info. I agree with you, it doesn't make a lot of sense. From what I've read here and other info sites, the VATS works, or doesn't. I don't know if there is a great difference between you car and my 91. I was told by Noe that they could bypass the VATS easily up to 88, but after that it was something they don't do. Could be an insurance issue.
Subman

 

I would be very interested in the outcome, it does sound more like a bad module.

 

jfb & Skybolt - Got the car back a day early. Spoke to the tech that replaced the tumbler & keys. He was not mystified that this was the problem. Apparently this has happened before, which is why the diagnoses was so quick. Following the logic of the VATS, I would have never guessed that this could be the problem. I was ready to start tracing wires looking for frayed, shorted, crossed, chafed wires. Just as glad I took it to the shop. The headaches and frustration weren't worth it.
Thanks again for all the help!
Subman

 

Following advice from some here, I stopped suspecting the vats. I have spent a great deal of time and money and still don't have injectors that fire. I don't know how the car "knows" that the vats is bad after the CCM AND ECM have been replaced, but I bet this is my problem.

 

There are times when we have an issue with our beloved C4s, that when we have the time, patience and knowledge, it is a joy to work on and do the fix. Unfortunately, most times, we have none of the above and it just makes sense to seek professional help. I have a rule of thumb that I go by: if I can't track down the trouble in four hours, it's off to the pros to sort out. Now many times, rather to my surprise, I have found the problem rather quickly (bad relays, wire connectors, DOA MAP, blown fuses, etc.) but when it becomes a grind I'm outta there! I have violated the four hour rule on occassion when the problem didn't affect driveability or safety and usually I'll muck through and make the fix. When I'm tracking down some mysterious malady, I find that my service manual is invaluable but I never spend more than one hour at a time actually working on the problem. I am more likely to sit back and think through what I have done so that I'm not chasing my tail. An occasional brain fart while I'm bending at the waist, my back is killing me and my attention is otherwise distracted can lead can lead me to oversight; the damn problem is right under my nose and I don't see it. One unbreakable rule I adhere to is, NEVER throw parts (and money) at a problem! A lot of folks do that and then end up taking it to a garage for repair. If I'm pressed for time I wait for another day. In my lifetime, I've screwed up a lot of things because I was in a hurry, got short on patience or got angry at a piece of machinery. Knowledge, tools and patience. The most important lesson I've learned in over 55 years of wrenching. One other thing; cars are wonderfully complex machinery that can give one great joy and pride of ownship. They can also be ornery, nasty, miserable SOB's when they aren't running right! So the choice comes down to: "Do I shoot the SOB or try to fix it?" Might as well go ahead and fix it so you won't have to patch the bullet hole when you get it running.

 

LOL - I too have learned the lessons- cars are a losing proposition from the get go. For a lot of us, cars are a passion and a hobby and that passion outweights the financial common sense.