You should be able to induce a distributor reference signal to to ECM. When the ECM detects a distributor ref signal, it WILL pulse the injectors. I think you're not getting a signal to the ECM. I had two bad computers in a row. You cannot guess. You must test.
I'm not sure which ECM you are using, but all GM are similar. A GM service manual for the system you are dealing with will be invaluable. FACTORY SERVICE manual.
