When I had a JDM SPi Mini (Still miss that car!) the vacuum line that went to the bottom of the air intake would fall out occasionally and the car wouldn't start. I hope it's something simple like that for you!

Is the tach moving at all? It could be the crank sensor. You won't find any injectors for the spi as it has a throttle body single point injection the MPI is multi point injection.
Make sure all the vacuum lines are good especially the elbows they tend to crack with age and leak air giving a lean mixture which the ecu compensates with and richens it up, there should be around 8 of them total.

fmix. did you check ALL your fuses?/ I have had to have an SPI throttle rebuilt in the past . from Burlen Fuel..in the UK.. also might be ECU problem..( also had ECU units rebuilt from minispares.com    you  got to remember this SPI are 20 years old now..  might be time to just convert to carb..Malsal might chime in on this..  later bc

Hey guys, my JDM SPI had been starting to have trouble restarting after being warmed up like when I would go for a drive, get gas, then try to leave.  The car would get a quick sputter and die.  Hold the key on for 5 sec and it would eventually fire.  I drove it last Sunday no problems.  Wednesday it refuses to start no matter how long I hold the key on.  I tried again Thursday since I had a little more free time and checked around for loose connections and odd unburned gas smells.  Nothing.  Today I took the plugs out of the middle two holes, not sure firing order but #2 and #3 when looking at engine.  Plugs are dry maybe look a little on the lean side for carbon build up.  I test spark and the color is a bit orange, sometimes weak sometimes strong.  Probably need a replacement coil or rotor, but I do have spark.

Plugs, wires, and air filter were replaced last year when I bought the Mini.  Fuel filter was replaced a couple months ago along with exhaust.  When I took the collector off the header the cut out for the O2 sensor was a bit on the lean looking side too.  So I am wondering if maybe my injector is going out, or needs to be cleaned?  This weekend I will maybe do a fuel line test to see if the pump is working and my friend is coming over with a multimeter to measure the coil.

Anything I missed?  Any tricks or tips?  Are SPI injectors available anywhere at all?  I have found MPI ones, but never SPI.  Battery is good, starter cranks strongly, gas tank is pretty full with fairly new gas.