I had 2 episodes this week where the car wouldn't turn over, it wasn't battery or electrical. It would act like it was a fuel injection or spark issue. If I let it sit for a couple minutes after it failed to start, then it turned over and would run normally for a couple days. No common theme of the car being cold or hot. Anyone else had this happen? It's at the dealer now and of course the problem won't repeat itself for the service dept.

 

Sorry to hear about your issue, Braindoc1. I think it happened to me once.
A couple of questions:
1. When this happens, did you ensure the car was in park / neutral turn the key off and remove, and then retry it?
2. Was there any notification on the LCD display?
3. Did this start to happen while in automatic shut down?
4. When you say turn over I'm assuming the auto start function does not activate the starter motor, not the starter motor automatically turns the engine for 15-20 seconds but nothing happens and you have to take the key out to stop the starter motor from turning over. Is that correct?

ChuckJ

 

Thanks for replying ChuckJ, in answer to your questions...
1) I have keyless start, so I didn't remove the faux fob. I also have a 7 spd, clutch engaged each time.
2) no notification on theLCD of any error, and no error message in the computer when dealer queried the system
3) because I have a 7 spd, I didn't think to shut off the auto start/stop until the second and last time it did this, some don't know if that's a factor but I mentions Ethan to the dealer and they say they ruled that out.
4) if I understand this question, the motor is not engaging fron the starter, but it's not giving me the " clicking" I'm used to with a bad starter. It sounds completely normal as a normal start but the motor never engages. That is why I wonder if it's a fuel injector issue.

Thanks for your diagnostic help.

 

I'm thinking electrical / battery. One thing I have noticed with my car is that if I let it sit overnight, when I turn the key on (not the engine) and let it sit for 15 seconds, the battery gets down to 12 volts quickly. When it's warmed it takes a lot longer to get there. When my 2007 was getting an old battery it used to do the same thing and in fact get down to 10.5 volts when the starter was engaged. My 991 gets down to 11.8 currently in 60 degree ambient temperatures. You might want to see what yours is and eliminate a bad battery diagnosis (could be you've got a cell shorting).

ChuckJ

 

Maybe, though that would be surprising as I only have 6k miles on it and it was a custom order thus it wasn't sitting around on the lot at all. The first time it happened it had been sitting 90 minutes, the second only 15.

 

Did the dealer check the battery charge? Were any error codes present when hooked up to the diagnostic computer at the dealer?

 

Battery charge was fine and no error codes appeared when they checked the PCM.

 

Ask them to change the battery out and drive a few weeks with a replacement battery to completely eliminate that possibility.

 

That's a good idea.

 

ChuckJ, how do know the current voltage for your battery? Is there a readout in the PCM I'm missing, or are you using an external voltmeter?

 

I figured out how to get the voltage reading; it probably would have taken two seconds if I had read the manual, but I'm allergic to manuals.
The interesting thing I noticed is that the reading drops quite rapidly between modes of operation (it goes back when you go back to that mode, though). This is what I see:
Sport or Sport+: 14.9V
Normal: 13.7V
Normal with stop/start on, stopped at a light: 12.1V
I love this additional piece of info to look at, I'll be having fun with this for a while!

 

Don't believe the gauge will tell you that your battery is on the way out. It's an idiot light equivalent that is too late to rectify a problem. Just my 2 cents. I replaced several batteries in my Porsche's and the best indicator was the fact the all the dashboard lights dim when you start the engine... by then.. you better make your next trip to get a new battery.

 

you have a stick shift - right? Check the clutch start interface. This has been a common problem in the past on both 997.1 and 2's. If the clutch isn't fully depressed or the interface is not properly aligned, the car will not start. Don't know about 991's but it's an easy thing to check.

 

Hepmonk:
The new digital readout has volts available, you just have to set it up per the manual. To see it when you start the car you have to close the door and put your seat belt on before you start it.

ChuckJ

 

Actually, the 991 has a digital readout (see my post above).

ChuckJ