Hi please help. I am out of ideas...

Got into the truck to drive one day and she died on me. First she idled fine, then stalled when I put the transmission into drive. Now she won't start at all. The engine cranks but won't fire up. I have spark on 1-4 and I have fuel pressure up to the rail. I've tested resistance on all of the sensors and injectors (within specs) and I haven't found a blown fuse or link. My suspicion is that the ECU is toast, although I can't see any visible flaws in the circuitry. I have no codes popping up, and when I go to check the diagnostic harness it reads only that the ECU is functioning normally. I have an extra ECU from a 95 MM M/T but I don't think it will work in an auto. This is driving me nuts!

What else can I try? Why does she turn over but not start?

1994 MM 2.4 Auto