ECU is good so that is ruled out.

One thing I noticed is when the key is in the ignition but not turned at all, the security light flashes on the center console along with the key light. Both flash constantly. Starting to think the whole issue is somewhere related to the security system. I havent had time to mess with it but would appreciate any other guesses. If not, looks like the engine is coming back out and it will be for sale as a roller next week.

 

I had an issue with this when I had my motor built and injectors swapped. I wasn't getting a proper 12V to the switched power on the ECU when cranking so it would throw the injectors to a very low duty cycle which was too low to start the car unless I used starting fluid. Then it would run on its own because I wasn't cranking and drawing power away from the ECU. The problem in that case turned out to be a bad battery cable but I assume your battery is in the stock location so there's no real cable. I would pull the connector out of the ECU and put a Multimeter in the switch power pin while cranking to verify 12V to verify the switched power wire is good all the way through.

Hope this helps,
Ryan

 

I fought this demon for over 2 years before I figured out the problem. I had a sneaking suspicion that when I replaced my flaky cpu #2 with one I bought off the forum is when it all started. It was also very intermittent, in fact, it didn't do it for a whole year. Then the problem returned right before I was set to take the car to AZ. I worked my way back from the ignition switch with a test light and when I touched the one wire coming out of cpu #2 I noticed it lit up slightly, but not fully. After bypassing the security relay, it's good to go now, but my security system is still flaky. When I lock my doors I have to lock, unlock, and lock again, or it will trip the alarm next time I unlock the drivers door. Have you tried jumping the solenoid? That's how I eliminated the starter as the culprit on mine, even though I already replaced it 2x (got a bad replacement the first time). I still have my old cpu #2 and I'm going to attempt to rebuild it.

 

Wanted to update everyone on this thread just in case someone else encounters a similar issue going forward.

I sent the car to the guys at Addicted Performance Unlimited for them to take a look at it with the arrival of our newborn child I was out of time. Zach and the guys there found the issue in under an hour. On automatic cars(this car was swapped to manual) Mazda decided they would make two sets of blue connectors be identical over by the ECU. Someone before me plugged the blue connector that is supposed to connect to the engine harness into the blue connector that goes to the dash harness. When I installed the engine I plugged the large blue connector(sorry not looking at a diagram to name the connector right now) on the engine/emissions harness into the unused blue connector hanging there by the ecu.

With these connectors backwards it was like the starter interlock was never bypassed. This caused the no click, no crank start. I'm embarrassed that I spent one day(literally) swapping parts around and never thought to check all the connectors over by the ecu(even when changing out multiple ecus). Oh well, I learned something new and hopefully this will help someone down the road.

Thanks again to Addicted Performance who had seen a similar situation before and fixed the issue very quickly.

 

from this thread which is basically the same thing, and covers the entire starting system.

https://www.rx7club.com/3rd-generati...-872841/page1/

make sure this isn't happening....


from this thread which is basically the same thing, and covers the entire starting system...

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/one-possible-fix-click-click-start-problem-remove-oem-security-relay-872841/page1/