Hi,

With the possibility of this reply being totally worthless, here goes.
I know quite well how the MEFI 4 system work but I am not familiar with the MEFI 5.

In the MEFI 4 you would have a Delco EST Distributor with an Ignition Module with 2 connectors.
The Ignition module would in fact tell the ECU that the engine is turning and if the ECU gets not signal this way it would not open the injectors.
Granted, mine is a TBI-engine and might be totally different.

The Ignition module would also, I think, get the coil to "fire".

If the ignition module is faulty or the distributor shaft has lost its magnetization you would probably end up with two conditions.
1) The injectors would not fire.
2) The coil would provide no spark.

One test to do would be to hook up a LED in place of one of the injectors. Crank the engine and the LED should flash.
If it doesn't the ECU is not sending a signal to the injectors to fire and you have either a problem with distributor/ignition module or the ECU, or of course, wiring.

With the TBI you could easily test for this by pouring a small shot of gasoline down the throat of the throttle body and the engine would run fine for 1-2 seconds.
With an MPI I guess this is much harder...

I think you can bypass the functionality of the Ignition Module by putting the engine in service-mode, this is what you would do when setting initial timing or base timing of the engine. Again for MEFI 4, this would be to put a paperclip between two terminals of the diacom connector. That would get the ECM to ignore the signals from the ignition module.

Hopefully the MEFI 5 is somewhat similar and this might provide some help, otherwise, disregard this... =)