i tried posting this at miata.net but no one is helping out?
I'm trying to help a friend diagnose his no start issue on his 92 1.6L and I am leaning towards a bad PCM. I have read the No-start troubleshooting thread and the only thing I haven't checked is having power at the "X" terminal on the ecu. I have no idea which pin it is as I don't have access to a factory service manual or enthusiast manual unless I missed an online version. If I did, direct me in the right direct please! lol. Anyway, here is the rundown on what the car is doing and what I have done so far in my attempts to resolve the issue. Let me know what you guys think. In short, the injectors don't seem to be firing.

-Fuel pressure is around 40psi while cranking so the pump is working(Confirmed via inline gauge)
-All 4 spark plugs are firing (The car will attempt to start when given some starting fluid)
-Compression checks out
-Fuel Inj relay is working (I removed the cover and watched it operate correctly and even activated it by hand) I also noticed that the IACV clicks when the relay engages. Is that normal?
-I am getting no pulse on the injectors (Confirmed via noids/test light)
-CEL showed code 3
-I pulled the PCM and visually inspected it, but did not find any definitive burn marks. I assume there could still be an internal malfunction?

So as you can see, it appears I have narrowed it down to the PCM unless there is something else that controls/influences the injectors??? The IACV I believe is also acting up as the car idled at 1000rpm before it stopped running altogether. Could a bad IACV kill the PCM or inhibit starts? I come from working on mitsubishi's and on some cars a bad IACV can kill the PCM. Is that something to worry about in the miata circuitry? I'd hate to try another ecu only to kill it. Thanks for the help!

 

The fact that your CEL is actually giving you codes makes me want to beleive that the computer is fine.
You might want to tell everyone what a "code 3" is.

EDIT: Here is your ecu pin diagram if you really want to test voltages.
http://www.miata.net/garage/ECU_Pin-Out.png

If by code 3 you mean G signal, swap your CAS with a known working one and see if it starts.

 

Code 3 is problem with CAS signal. There is either a problem with the CAS wiring, or the CAS itself is dead.

No CAS = No fuel

 

Doesn't the CAS also control the spark events? Spark is fine. Are they on separate signals or something? Guess we'll grab a CAS and try it.

 

Not sure on the specifics but theres a G signal and some other signal (I forgot the name). It could be that one controls fuel and one controls ign, I couldn't tell you.