TDI Engine Starting Problems: 2.5 V6

Good morning, everyone!

I have already read here and in many other forums, and I've seen various posts about the same problem, but nowhere does it mention a solution. That's why I'm describing the issue/asking my question:

My 132 kW 2.5 V6 TDI, manufactured in 2004, starts perfectly well in freezing temperatures after the glow plugs have been activated. It also starts well when it's warm. However, if it sits for several hours after being driven, the glow plugs don't activate, even though the engine is very cold. Then, it cranks for a long time and starts with a plume of gray smoke.

Der Temp.fühler ist schon getauscht, das brachte keine Verbesserung. Mein Schrauber sagt über Adaptionsgruppe 12 kann man nur die Vorglühzeit einstellen. Ich würde aber das Problem gerne lösen indem ein längeres Vorglühen auch bei wärmerem Kühlwasser eingestellt wird. Ist das Sure, I can do that. Please provide the text you would like me to translate from German to English.

Thank you for any tips in advance, and best regards.

Björn.

First, please read the relevant articles.

Specifically, this one: https://community.dieselschrauber.org/en/viewtopic.php?t=11122
He already answers some of your questions.

Otherwise, there's already plenty of discussion in this forum regarding starting problems with the 2.5 TDI engine.

I've already read the article, but it only discusses preheating TIMES. I would like to solve the problem by having it preheat even at, for example, 10 degrees Celsius water temperature. And I can't find any instructions for this online.

I have also read the various articles, and they repeatedly suggest replacing the temperature sensor. I have already done that, but there has been no change.

The starting and fuel injection seem to be working fine; it starts perfectly even when it's ice cold. However, after driving for about 5 kilometers and then sitting idle for three hours in temperatures of -10 degrees Celsius, it doesn't warm up again and starts very poorly.

Greetings.

Björn.

What you're doing there is more of a symptomatic treatment, but in general, the glow parameters can be adjusted via software as desired.
Find a skilled chip tuner who can do it for you... I mean, Rainer might even be able to do it legally .

That's also what I meant when I referred to the technical article.
It doesn't make sense to change the preheating times/temperatures because the problem lies in the hardware. You need to find that.

What have you done so far?

Since I don't have much technical knowledge myself, I rely on my trusted mechanic. They checked all the dates (start of warranty, etc.), inspected and replaced the fuel injectors, replaced the temperature sensor, replaced the diesel filter, and checked the diesel lines for leaks. No errors were found. The car has a complete and documented service history, and there has never been any compromise on maintenance costs. It runs great, doesn't smoke, doesn't consume oil, and only has this one issue.

Is the VP44 sealed? Has the O-ring been replaced?

Since you mentioned that the car starts poorly when it's been sitting for a while, that could be related to a leak in the ESP (Electronic Stability Program) system.

The fuel pump is sealed and working correctly. When it sits for days and then starts, it starts up perfectly after the preheating, so I don't understand why it doesn't do the same after a short drive and a brief period of inactivity...