As per Stewzer55;
Along with a power supply input from the battery, the ECM needs to see 2 things before it will allow the injectors to open and allow fuel into the throttle body. One of the following two permissives must be met at all times:
1. A crank signal (from the starter solenoid) that an attempt is being made to start the engine. This is only needed until the ignition system fires up - after that it goes away because you release the ignition switch from the START position and the solenoid is de-energized.
2. After the crank signal drops out, the pulsed signal from the distributor module takes it's place. As long as the ECM senses an operational ignition system it will permit injector function.
It is often possible to start the engine without a crank signal because the ignition system will fire up and provide the input to the ECM even without fuel.
But, as you can see, the opposite is not true. If the distributor module is not firing the plugs, the engine won't fire up regardless of whether you have fuel flow or not.
Bottom line - you can probably start an engine without a crank signal, but not without a functioning module due to the accompanying lack of spark in the ignition secondary (i.e at the plugs).
As a test, just pull and ground a spark plug and observe whether you get an arc across the electrodes. No matter what ever else, no spark = no start.
If you get a good spark at the plugs and you have tried 2 other ECM's - start looking at power supply issues to the ECM.
With the key on and the engine not running, do you get a steady Service Engine Soon light?