You mentioned you cleaned up the fuse box. If it is like the type shown here, you probably didn't get its hidden gremlins. The fuse holder brackets are riveted to the wire terminal tabs underneath and they suffer from oxidation of the brass, losing contact intermittently and then worse.

The remedy is to replace the fuse box. A cheap fix at $15 from our host.

You also need to verify you reconnected all the wires properly. Loss of fuel pressure due to a weak electrical connection would result in no-start.

I apologize, I had a computer issue and couldn't respond to the posts over the last 24 hrs. I really appreciate all the advice. I lost everything all at the same time while I was cleaning the connections on the fuse block. The car ran great prior to that. I replaced the relay box and that restored everything except I have no spark and no fuel delivery/the fuel pump doesn't activate. It seems the likely culprit is the ECU considering it manages those two functions. I'm thinking an ECU refurbishment makes sense. I've checked every fuse, I believe. Where is the fuel pump inertia switch located? Thanks, Steve

I can't remember if Suzy's '96 Cooper 35 had an immobiliser or not; I want to say it didn't, but she sold the car ~20 years ago and I didn't drive it much...  My '98 JDM SPi/MPi hybrid doesn't have one, and my 2000 Knightsbridge did.

I also seem to remember that there were two methods of operation - one was a fob, the other was a 2-prong key that got dabbed onto a socket on the dash.  Now I've typed that I'm wondering if the Cooper 35 had it.
Knowing our domestic market, they were probably a cost-option at time of ordering rather than being standard.
White/red is the wire from the ignition switch to the starter relay, which has a brown/red going to the starter motor.

4minis - have you checked the inline fuse to the fuel pump, and reset the fuel pump inertia switch ?

Both of those will prevent the car from starting.

Alex , +1 to what you wrote.

My question to you, are you familiar with the earlier SPIs? I've had mine for 30 years and never used the key fob for the security  ( the blinking red light). I did not want to get stuck here with a no start and no support.   I can't remember what pushing the FOB button does other than turning on the red light. Does my '94 have an immobilizer?

I remember the only problem I ever had with a no start was I was not getting any power from the inside of mini to the engine bay was with the large white/ small red wire going to the plug just outside the black box next to the servo. Made a jumper wire which solved the problem. Never investigated why just grateful it worked.

Coding an ECU to a car is a CANBUS issue, which shouldn't affect any Mini be it SPi or MPi as they use traditional wiring looms.

I'd suggest taking breath, counting to ten, and approach the cars logically instead of throwing money at them in futility and frustration.

Get a dark blue covered Haynes manual which covers the later cars; it doesn't look like our host sells them so feeBay or Amazon will be your go-to.  It's not a particularly good manual mechanically, but it does contain some pretty decent wiring diagrammes for the injected cars (I use the earlier ones when needed for mechanical jobs and the later one for electrical).

As already mentioned, start with the basics - battery condition, terminals, earthing points, switches, and fuses.  
Work your way through all of the circuits in a methodical and logical manner.

Do it yourself - you'll get to know the car better and it will save you from p*ssing money away.

Why would coding be necessary to plug in an ECU? There is nothing but electrical components that the ECU receives info from or feeds info to.

My limited knowledge of immobilizers tells me if that were the issue, the engine would not even turn over.

However, if you do suspect it is the immobilizer, I suggest you read the following:

https://donnlee.com/2007/08/30/rover-lucas-5as-immobilizer-a-alarm-system-info-rover-mini-cooper/

Just an update on this 1993 Mini. I removed the cable ends from the battery for 3 hours hoping that might reset the Immobilizer because it seems now that might be the problem. It still doesn't start. There are no dash lights when you turn the key on or while the vehicle is turning over. Is that a symptom of an immobilizer issue? Is there another way to reset the immobilizer? Thanks, Steve

Bill says "of course the ECU must be coded to the car."

(I'm just the messenger!)

I don't know about coding, never heard of it. I think it's a plug and play. What is coded is the immobilizer, which is something you don't want to use. Now that I'm thinking about this and writing this; Could that be your problem? I bet it is.

Does your mini have that option? There is a stand alone red LED bulb on your instrument cluster.

Borrowing one would be great favor. Does it have to be coded to the original car? Thanks, Steve

You have a later SPI. There are some eBay sellers with your ECU and I don't think is out of line in their pricing $300 to your door. I can lend you one to test. You will have to pay for shipping both ways. You probably would want to own one. Call me 631 Five Six Six 4989  Jim

"Bill Cox says MinSpares does not respond to emails. You have to telephone them.
" btw. their is also AcTronics in the Uk that can rebuild SPI EU units."

Have you tried calling them?

It's just a single plug ECU. I've sent 3 emails to Mini Spares in the UK for instructions and the cost, with no reply. I'm a little concerned at this point considering they seem to be the only game in town to get the ECU refurbished. Is there anyone else out there that does this? Thanks for the help.

Which ECU do you have? There is a two plug which is early and a single plug ecu? What is it costing to send your ECU back to England and have it repaired?

That's the best advice I've had yet. I just called the shop where it's sitting. During the 8 hours of troubleshooting, they found a bad fuse and replaced that relay box. All the electrical accessories now work; the only problem is no spark and no fuel injector pulse. When I got the Mini, it ran and everything worked, then it went black. At this point I'm blaming the ECU because that seems like an engine management central culprit. I'm planning on sending the ECU to Mini Spares to be refurbished. It would be great if someone in the US did that service. That's what I'm planning at this point. It's currently being flat bedded back to my house. It's odd that this Mini has no tow hooks or good spots to hook onto to drag it up othe flat bed. Considering the reliability , the manufacturer should have made certain it had a tow hook. My 1989 Mini has a tow hook. Thanks again, I'll let you know how it goes. Steve

The ECU is for engine management. You still should have power to the headlights, starter, power to the white/red wire to ignition & fuse box, accessories like horn, lights and wipers. ECU's should not cause a complete shutdown. Did you check to see if you have power to the starter? Not taking the word from your electrical guys.

I have a Haynes manual up to 1993. I guess that's why it was $12 online. I'll have to look for a later version. I did remove and clean/sand all grounds before I sent them to the auto electric shop. They exhausted every idea before they handed it back to me. It's being towed back to my house tomorrow. Because I lost everything suddenly, that's why I'm blaming it on the ECU. Planning on sending it off to Mini Spares to be refurbished. That was one of their suggestions.

Since we know you have two minis and a Haynes manual. It should be the latest one going to model year 2000. The electrical schematics are good and up to date.
Mini 1 which had a catastrophic  electrical failure. I would look at both battery connections and ground connections to the body in the boot. Unbolt the ground cable and sand the body and the lug.

With a multi meter test to see if you have 12v at the end at starter.

You have to start at the beginning.