If this is happening on a hot motor that has sat for 30 minutes to an hour and a half or so, what is likely is that the fuel film on the intake runners has evaporated. Cranking fuel is designed to add the necessary fuel to recreate the film on the intake runner and provide enough fuel to start and run the engine.
The fires, then dies symptom is usually a result of the priming shot firing the engine but there's not enough fuel to keep it running. There are however some other things that could effect this. Here's how I would troubleshoot.
1. Make sure that during cranking the system is seeing more than 10 volts. It takes more juice to start a hot engine, especially if you have a stock type starter. Check this while hot
2. Make sure the IAC (Idle Air Control) is set properly. With the engine warm and in park, it should read around 10 counts
3. Cranking Fuel is set either too high or too low. In your case, based on your testimony that adding throttle input does not help, leads me to believe the cranking fuel is set too low. IN small increments, adjust your cranking fuel upwards in your warm start area
4. Afterstart Fuel is set too high or too low. To set this, start the car and watch your AFR on the handheld. If the engine is struggling and running rough and the AFR's are increasing, you need more afterstart fuel. If the engine is choking and running rough while the AFR is decreasing, you need less afterstart fuel.
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-Jason
1969 Pontiac Firebird
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