It sparks so it's getting at least some of the reference signals. Not sure on your model what the schematic looks like. Have you tried the fuse?
Confirm the +12v to the injectors, the common hot remains hot when you crank it over and doesn't dump to 0 or some low voltage.
Look over the sensor circuit from crank, cam, dizzy wherever it all comes from. It's possible it could be getting ignition signals and not injector reference signal. The ECU on my hatch (OBD1) gets a "Set" or "Reset" signal from the start circuit. Then it looks for the TDC signal and references from there to fire plugs and injectors.
I don't have a schematic for your setup or I would look it over.
The dam thing is probably very similar in function to the P06 in my hatch.
Ring out the lines from engine position sensors to the ECU to ensure good continuity if you haven't already done that.
Sprinkle some Holy Water on the little ba$tard.
If I was in the neighborhood I'd swing on by and get down in the trenches with you over a couple of beers and a few Havana's. It took me a week on my hatch to debug it when I did the swap. Looking back, that was time well spent. Frustrating at times. But, now I know how that little MF works. I mean wire for wire how it works - no brag here. You will know yours real good when you're done with it. The knowledge may come in handy down the road.
Any fault codes? Are the injectors the same?