The van drives great (I replaced the spider injector 6 months ago to pass emission test). The a/c has not worked since we bought the car so I had it checked and they did a system check and toped off the R-12.
Two days later I'm driving the van without using the a/c and I turn the car on and off about 35 times throughout the day with no issues. I drive it later in the afternoon and use the a/c for about 20 minutes and I shut the van off and 2 seconds later I tried to start it (my wife and kids stayed in the car and I didn't want them to get to hot. Car would not start. I shut the a/c off and still would not start. After trying to get a ride (about an hour later), my wife tried it again and it started and drove great.
Drove it all over and stopped and started several times over the weekend with the a/c on and had no issues. Last night I tried to duplicate it to try to explain it to my mechanic and it wouldn't start after a quick (less than 2 seconds) start.
No codes, but after I checked the codes, it started and ran great.
Any ideas before I start chasing this down? ignition module? Temp sensor?

HINT to your mechanic: The fuel pump relay does not recycle unless the engine has been off for at least 10 seconds.

If any sensor, (ECM input) were to fail, even momentarily, a Diagnostic Trouble Code, or DTC, would be stored and the "Service Engine Soon" light would come on. If the SES comes on, or is already on, retrieve the code and diagnose from there. If the SES light does not come on, it could be one or more of several things that can/will NOT turn the SES light on when they fail. That list is huge and would include any ECM output such as fuel pump relay, wiring and or pump, ignition module, fuel injector or even possibly the ignition switch or corrosion at a connection, battery cable, or a body ground. You have a tough problem here. Intermittent problems are extremely difficult to identify, even for the seasoned professional. Persistence, patience, and possibly some money will be necessary on this one.