I'm living with this problem for a while now.

The engine will not start at all.

The engine will not start when hot but starts normally when cold.

The other day I had replaced my battery and as it had started again on quitting when hot was just sitting in the garage for a month or so.
I fired it up and it would start right away. To keep the battery charged I revved it to 2'000 rpm and kept it there for a minute or so.

At this time I got hesitations and drops in rpm (audible) but erratic rpm indications on the tach.

Got a new distributor (DELCO remanufactured) with a new IM (ignition module) and coils and bearings and - well a new distributor.
Will replace that one as next step and come back with the results.
Fortunately this time it is not running properly so I may be able to eliminate all other problems.
I'll post back with some troubleshooting information.

 

Finally distributor swapped. PITA

Couple of things to note when doing that swap. will look in the forum for a good write up else I'll write one.

It's running fine again. Starts up right away, idles nicely.

Coming to a better understanding of the 1994 VIN Z.

The no start or starts then dies right away issue associated with an IM is very hard to diagnose without a TECH I. Still had not time to check weather my ALDL cable could have detected the issue.

The starting sequence of the VIN Z is in open loop. That means that during startup the engine does not care about the rpm signal to the ECU. It simply takes the 0deg advance signal for the ignition timing upon startup and meters fuel accordingly until it turns above 400 rpm. Then the ECU should take over. This said it becomes clear why it sometimes can generate several no or hesitant start issues:

Correct me if i'm wrong but i found:

STARTS BUT DIES
It starts but dies right away - Can be either the signal to ECU for fuel injection or the IM (ignition module) itself not producing spark.
The detection could be with a spark tester as it should be visible that we may have no spark.

DOES NOT START AT ALL
This was my condition. The tricky part was. I had spark and I had fuel injected. This may lead to erroneously diagnose the fuel pump. The trouble shoot guide of the manual says listen for the 2 - 3 seconds running of the fuel pump which should stop with the key at ACC but not cranking it. Obviously GM assumes that its fuel pressure sensor does the job. Only if you have no spray from the injectors it goes into diagnose of the fuel system.
Then I had it start but idle normally for a while and when starting to settle for the lower idle it started erratically missing a step and I got an erratical rpm signal on the tach.

Once swapped the distributor and on a basic adjustment some 3 - 4 deg off 0 advance (no timing light) it started up right away, no hesitation, no missing firing or other issues. Drove it to my workplace where we have a timing light and did the fine adjustment with no issue.