EDIS Modules are self contained, meaning if they get Crank sensor pulses then they will run the coil pack, generate spark without computer input.
The computer hook up is to give computer fuel injector timing and RPM, computer sends the EDIS suggestions on spark advance and retard based on driver input(gas pedal, TPS)
One thing that can happen is mis-wiring in the START circuit, i.e. you have 12volts at EDIS and coil in RUN, but when key is turned to START voltage is cut.
So you would have no spark when cranking but all voltages are correct in RUN
The power for both comes from the EEC(PCM) Relay in a 1993, it also powers EEC(computer) and Fuel injectors.
I would test for power at coil connector while cranking, it will drop to 10volts but not to 0volts.
I think the 1987 powered the ignition via the NSS or Clutch switch when key was in START position, power from RUN position was cut at that time