Engine not starting

This sounds like a classic ignition module which they had big problems with. Here is the location so you can change it out to see what happens. If you did the ignition module with the distributor please test the EEC relay here is a guide to help with the location in the diagrams below:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

Replaced both relays and the TFI on this distributor doesn't have the three contacts at the rear and was replaced with new distributor.

no spark while cranking, but sparks once when cranking stops.

Lets try the EEC relay test or replacement. please let me know.

already replaced.

I have seen a fuel injector short out and cause this. can you disconnect all fuel injectors to see if the spark returns? Also disconnect all oxygen sensors as well. let me know.

still no spark.

Let's check the ignition switch if one "leg of the switch is bad it will not get complete power to the ECM. here is a guide to help and the ignition switch wiring diagrams below:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

Check out the diagrams (below). Please let us know what happens.