Car won't start (no spark/injector pulse) long read

[Import_Ant]

Well I'm really pulling my hair out at this point. I guess I should start from the beginning.

The car is a 1990 240sx FB (bone stock mechanically)

I had a nice sunny Sunday to do some general maintenance on my car and so I changed the oil and decided to try and diagnose why my illumination lights wouldn't come on in my gauge cluster. I dropped the steering column, pulled the gauge cluster, looked for any leaky capacitors then put the gauge cluster back in. Then I took the TCU out of my brother's 89 coupe and plugged it in. turned on parking lights and my illumination lights came on too! awesome. problem fixed. I go to back my car out of the garage and it sits and turns over but no start. ****...

At first I thought my CAS went out in my distributor. no spark, no injector pulse. So I replaced my distributor. still nothing, I thought maybe the store gave me a bad distributor so I have had it warrantied out... 4 times! took it to a shop and they are saying the same thing (seems like a bad distributor)

I had the harness tested for resistance. there are no broken wires between the harness going to the distributor and ECU. The distributor is now (after the 5th one) sending all correct signals to the harness at the ECU (crank angle refrence signal and injector refrence signal) ok I have a good distributor now. must be a bad ECU. I tried two other ECU's (one from a late-model 89' and other from a mid-90) neither fixed the problem. I tried a new ignition, that didnt work (with any of the ECU's)

I'm going to try reverse testing my parts on my brother's car this coming weekend but I am really running out of ideas.

Does anyone have any other suggestions? I know the motor's good, the car drove into the garage before it quit. I tried running my brother's car without the TCU installed, it runs fine (TCU just controls timing of the wipers, defrost, and dimming function of the illumination lights) I tried putting my old TCU back on, disconnecting it, nothing changes.

Sorry this is so long I didn't want to leave any details out.

help mee

Thanks in advance,Aaron

(sidenote, are all 89-90 ecu's compatable? Is there some change that makes it where the given ECU will only work with that 'period' of Ka24e motor? i know there was a sensor added in late 89 when Nissan upped the compression to 9:1 does that effect anything?)