rk-d

+1

or fuel filter? Wouldn't bad crank position sensor trigger a CEL?

pfan

No. And that adds to the the frustration when it starts just fine for the dealer.

Needsdecaf

Just did a cold start and a warm start. Seems ok. Idle still fluctuates a bit between 600 and 700...,,normal?

Pmorritt

I vote for crank position sensor. Wife's MBZ started doing exact same symptoms. Cold ok, stopped for gas and then no restart. Waited 10 mins and presto perfect startup. I thought it was the immobilizer. Took it to my MBZ guy and he said immediately it was the CPS due to age and heat. He had several on hand as its common.

StormRune

I just got in my car after a short stop for lunch when I saw your post pop up on my phone. I watched mine and saw a constant wiggle between what looked to me about 650 and 700.

That sounds pretty reasonable to me too. As I think about it, if it was the fuel pump pressure fizzling out like I first offered I think the car's sensor's detect that. I imagine with the high pressure fuel pumps on our cars they have sensors that monitor that (my truck was an old-fashioned low pressure system). I also recall seeing the crank position sensor mentioned a few times, it may have been on the 997 forum for 997.2s, but I imagine that is the same here.