Tiguan 2.0 TDI: Intermittent Starting Issues (Warm Engine)

Sure, here's the translation:

"Hi there," or "Hello," or "Good morning."
I have a 2010 Tiguan, 2.0 TDI, manual transmission, 4Motion, engine code CBAB, common rail. Unfortunately, the engine occasionally acts up. Maybe you can give me some tips on how to narrow down the problem. Or perhaps someone even knows this specific issue. That would be the best.
"Problem: The vehicle always starts perfectly when cold, regardless of the outside temperature. However, when I turn it off while it's warm, it occasionally only starts after 2-5 attempts after a standstill of 5-15 minutes. This issue is not reproducible. Sometimes it runs for a week without any problems, and then it happens again. There's no discernible pattern. In the problem cases, the starting behavior is as follows: I press the clutch, turn the ignition key to the start position and hold it for several seconds. The starter engages, the engine turns, it seems like it wants to start, but then it immediately dies. The process lasts no more than one second. It's not like it's struggling for seconds as if it's not getting any diesel. The starter engages, the engine seems to rotate about half a revolution, it seems like it wants to run, and then it cuts out again. As I said, all of this happens within one second. All the lights in the dashboard remain on. There are also no obvious signs that the engine management system is intervening. There are also no error codes."
What has been done so far?
- Replaced the crankshaft sensor for engine speed.
- Main grounding connections checked. Battery/body and transmission/body.
- All connections to the starter motor have been checked.
- Batterie ist neuwertig. Belastungstest gemacht. Okay.
- Voltage measured at the magnetic switch during the startup process. The voltage is only present for approximately 1 second.
- Voltage was measured at the cable leading to the magnetic switch while it was disconnected. During starting, voltage is present as long as the ignition key is turned. The voltage is only interrupted when the clutch is released. Pressing the clutch restores the voltage.
It seems like some condition is being met that is causing the MSG or BNSG to shut down again after a second. Or could it be a fuel supply issue? Unfortunately, I also don't know which conditions must be met to perform a successful start-up. Besides pressing the clutch.
"Does anyone have any ideas on how I can narrow down the cause of this issue? It's really frustrating that the error isn't happening consistently. At first, I thought I could just keep driving until it finally appeared, but that's also annoying in the long run."
Thank you in advance.
Regards,
Burkhard.

Hi, it appears that this system is not ours, therefore:
https://shop.dieselschrauber.org/en/obd-support-key-p-112.php

Best regards, Rainer.

Hello,
Purchased approximately 15 years ago from the VCDS shop at PCI Tuning. Best regards.

Yes, and?

Hello,
I watched the tiger again today.
I read the rail pressure using VCDS. From my perspective, it appears normal. The actual value follows the target value. Even during a failed start, as described above, there is rail pressure present. As soon as the starter motor turns, the rail pressure immediately increases to 250-280 bar. Also, immediately after a failed start, the rail pressure can still be seen, at approximately 240 bar, as long as the ignition is not turned off.

Then I also disconnected the AGR valve. There's a thin piece of metal at the entrance to the AGR. Unfortunately, this didn't work either. It still results in a failed start.

Does anyone have any other ideas?

Generaldirektor wrote:

Hello, I watched the tiger again today. I read the rail pressure using VCDS. From my perspective, it appears normal. The actual value follows the target value. Even during a failed start, as described above, there is rail pressure present. As soon as the starter motor turns, the rail pressure immediately increases to 250-280 bar. Also, immediately after a failed start, the rail pressure can still be seen, at approximately 240 bar, as long as the ignition is not turned off. Then I also disconnected the AGR valve. There's a thin piece of metal at the entrance to the AGR. Unfortunately, this didn't work either. It still results in a failed start. Does anyone have any other ideas??

Sure.