2000 E430 crank position or alternator
 

Intermittently - car cranks but but does not start. On the way to work in the morning - got off the highway & came to a stop and car died. Started right up after about 5 minutes.

So far -

New battery
Checked for codes - none
No warning on display

Ran a/c diagnostic and 24 showed only rose to 10.5 when car wouldnt start. Rose to 13.5 when running. Dropped to 13 when all accessories running.

Belt feels tight no cracks. Hear humming from rear of engine when key is in position 2.

Thinking either...

CPS
Voltage Regulator
Alternator

How do I know which one is the culprit? :confused:

If the engine dies and turns over but won't start, then I would first suspect the CPS.

CPS

I'd go with the crank position sensor. Sometimes they wont set a code. Many bad ones I've dealt with need more than 5 minutes to cool off. 30 minutes to an hour is what I'm accustomed to seeing. If the car dies, then spins over but wont start, and then you spray water on it and the engine starts, you found the problem for sure.

Is there any way to be 100% sure without taking the alternator out or taking it to the stealer?

Reason I ask is because I dont read over 13.5 when engine is running using ac diagnostic...

http://www.ehow.com/how_4601849_verify-alternator-working.html

Also - I disconnected negative battery terminal while engine was running and engine didnt die.

http://www.ehow.com/how_4519042_check-vehicle-alternator.html

These facts seem to contradict each other to me. :confused: