Cranks but won't start, sometimes

[1993Saturn]

My engine starts fine, except for one particular situation. While turning over the engine to start, if I release the key before the engine fires, I will not be able to start it until I wait at least 5 - 10 minutes. If I try any sooner than that, the starter will just crank and the engine will not start.
What is the great mystery?

 

[Themightyquinn]

Does this happen when the engine is cold or warm or both?
Are you priming the fuel pump when attempting restart? Low fuel pressure is the most common cause of hard starting. What are both conditions for initially starting the engine and it either starting or not. I would measure the fuel pressure and compare it to specs. Haynes manuals have the different specs for fuel pressure.

 

[1993Saturn]

Sorry I took so long to respond. I have been working on the Ex for 3 solid days till dark on a bunch of stuff, including replacing the tranny. I couldn't work very fast partially because of the heat. Finally got smart and put a swamp cooler next to the Ex and it made a difference I keep forgetting to buy a creeper. GRRR!
Anyway, I have good fuel pressure. I replaced the ignition module of the radiater core support in front of the battery. I used a junk yard dog. $10 is cheaper than $150 over the counter. Solved my problem, at least for now (knock on wood).
Thanks.