Starting issue
 

Good Morning.
First post, and I'm looking for advice
I have a 2007 cayenne S v8. It has a regular intermittent problem when starting.
When I turn the key to start it will crank the engine then disengage the starter before the engine has fired. after a few more attempts, the starter will crank the engine correctly and the engine will start.
The "disengagement" of the starter. Is it an issue with the ignition switch, or starter motor? has anybody had this issue before.
Thanks in advance
Roger

rogerxu1;

Had a similar issue on my 2006 S with +188k miles.

What I saw was that initially if i turned the key and then continued, it would crank for 1-2 sec then stop. The engine would not re-crank until i turned of the key all the way "off" then re attempted.
However if I turned the key and waited +15 sec then attempted to crank, it would start and fire up. That went on for a few weeks then eventually the starter failed. New Bosch AGM Blue top Battery at the time.
I had to replace starter, pull off upper intake plenum, etc. I did complete coolant service, replaced thermostat, gaskets, "O-rings", waterpump, clean throttlebody, vaccuum hard line/hose, etc. Big Job! I did it all at home.
I know there are some electrical ground issues through out the car. But managed to get it running back then....

I definitely suspect the starter......

Hope this reply helps a bit.
Please keep us posted....God Bless You, Later....

I have posted about this issue before, however, at the risk of being thought of as a bitter one issue old man, here we go again. Neither a 2007 nor a 2006 Cayenne will recognize an AGM battery and therefore the battery will not be charged correctly. The charging system will overcharge and damage the battery. After about a year of not starting correctly my Cayenne S finally would not start at all. The independent garage said I needed a new starter. I had done some research and told them that, prior to replacing the starter, to throw my one year old AGM battery away and put a proper battery in. We would go from there and see what happens. That was one year ago and all is well. Have not replaced the starter. Also, a damaged AGM battery will check out as good if the garage uses a standard battery checker, they need to use a dedicated AGM battery checker. The first post says nothing about the battery, however, the symptoms appear to be the same as what I experienced. The second post does mention an AGM battery. High probability it is damaged. I have only thoughts of corporate greed as to why the battery manufacturers recommend AGM battery for our middle-age Porsche's.

Lol. I replaced my '04 Cayenne's AGM battery at 10 years. Nothing wrong with it, just didn't want to push my luck after 1 decade. And yes, it got another AGM battery.
My '82 928 has an AGM with absolutely no issues. I also use them in my motorcycles and typically get 5 to 6 years vs 2 years from a standard lead acid.