've researched this issue for some time, thought I'd post for some direct input. My stock 996 runs well, but when I run it to optimal temperature, like a quick errand, and park it somewhere for a few minutes, then try and start it .... it cranks for 10 seconds or longer (sometimes needs 4-5 attempts) before it stumbles to fire up. When it does start, it seems the engine is stumbling a bit at first, on occasion will die and I repeat the process. There is also a strong fuel smell during this cranking process.

The cranking itself is energetic, the battery is new. I have no other starting issues, just hot starts. I did get a CEL code: P0448;"Evaporative Emission Control System Vent Valve/Solenoid Circuit Shorted" per P0448 Evaporative Emission Control System Vent Valve/Solenoid Circuit Shorted, so yesterday I replaced the Fuel Tank Vent Valve on Filler Neck (Bleeder Valve), and the code has not resurfaced. I have test run the car a couple of times since valve replacement, and am now able to say that the situation has improved somewhat. Now it will hot crank about 4-5 seconds (maybe 2 attempts) and will fire. Still not like it used to do, (or as it will cold, now) one turn of the key, 1-2 seconds of cranking and it fires.

Things I am considering trying now at this point are (in order):
- Fuel pump relay, some have reported success, cheap solution ($15)
- CPS, seems like a highly talked about solution for my issue with a moderate rate of success.
- Fuel Pump, many reported similar problems that this fixed, but ouch$$$!
- Coolant temp sensor, I read one or two folks had my issue and this fixed it.

So my question now is.... Is my list in the right order and is there something I've missed here? Any/All suggestions are greatly appreciated!!!
Thanks!

Update 3/24/14
After an hour long "test" run, I shut off the car for 45 minutes or so, came back and it took 20+ seconds of cranking until it stumbled up and fired. Ran great after a couple revs. So problem still there.

 

CPS was my first thought. A malfunctioning crank postion sensor tends to function cold, and malfunction hot. I would begin there. Good luck.