Engine Starting Problems (2.5 TDI)

Hello community,

Sure, here is the translation of the text from German to English:

"The following is the initial situation:"

Audi A4 Avant, engine code BDG, 120 kW / 163 hp, manufactured in 2004, mileage 350,000 km, Euro4 emissions standard.

The vehicle starts very poorly and reluctantly with regular diesel fuel containing 7% biofuel (regardless of brand or gas station). It is not uncommon for the starter motor to have to work for up to 10 seconds before the engine finally starts. During this process, the car emits a strong cloud of white smoke from the exhaust, and occasionally a warning message appears in the driver information system indicating that the third brake light is defective. Once the engine is running, there are no problems; it runs smoothly and quietly, and the error message regarding the third brake light disappears within about 10 seconds. This behavior occurs in approximately 90% of all starting attempts. Subjectively, I have noticed that the problem seems to occur less frequently in cold temperatures. When the engine is at operating temperature, it starts immediately without the difficulties described above.

However, when I use the premium diesel from either of the two well-known fuel brands, the engine starts without any difficulty on the first try. This is evident immediately after refueling with the premium fuel: For example, I filled up with Ar*l Ultimate the day before, drove 10km home, and the next morning there were no problems starting the engine in cold conditions.

What has been reviewed so far?
- Glow plugs (all new)
- G62 sensor.
- Ignition timing
- Starter speed
- Battery (new)
- No air bubbles in the system.

A friend of mine suggested that I have the injectors cleaned, as they might not be injecting fuel properly after 350,000 kilometers and 19 years.

I then called a specialized company in Munich, but they advised against it. They said it would be a waste of money because the problem is most likely with the VP44 injection pump, which has mechanically worn out. Replacing the injection pump and having it coded would cost me approximately €2,500, which they considered not worthwhile.

Since filling up my diesel car currently costs around €140 per tank (at €2.20 per liter), and I don't want to simply give up the car, I need some help: Where else can I look for solutions to this problem?

I would therefore be grateful for any advice you can offer!

Best regards and a happy new year.
netrocker

Have the start date of funding and tax periods been verified?

Rüdi wrote:

Has the start of funding and tax deadlines been checked?

Yes, it has been checked.

Compression OK?

Are the camshafts and roller rocker arms all intact?

I can imagine that various factors might be contributing to this issue: fuel quality, poor compression values, injectors that don't reach the correct opening pressure or are leaking and dripping.

The camshafts should be fine. A visual inspection of the oil inlet doesn't reveal any abnormalities. I can't say anything about the lifters.

To the best of my knowledge, compression was reviewed some time ago, but I'm not entirely sure anymore.

This problem has been following me for several years now, and it's not getting better, but it's also not getting worse.

The idea about the nozzles seems most plausible to me... which makes more sense: having them cleaned or replaced?

Hi there,

Quote:

This problem has been bothering me for several years now; it's not getting better, but it's also not getting worse.

How many years? Approximately at what mileage did this start?
When you see a mileage of 350,000 km initially, one might suspect wear and tear as a potential problem (e.g., turbocharger, fuel injection pump, injectors, cylinder head). However, if the issue started 10 years ago at 150,000 km and has persisted unchanged, wear and tear is less likely to be the cause.
You need to provide more specific information. For example, were the valve timings checked by you personally, or by someone else, and how?
Apparently, the only issue is a poor start with standard diesel fuel when the engine is cold.
hg
Herbert.

Even though the difference in diesel consumption doesn't suggest it, I would definitely want to rule out the battery as a potential cause. If the car starts more easily with a jump start from another vehicle, I would replace the old battery without hesitation with a new Varta or similar brand.

Hello,

The problem has actually existed for almost 10 years and started around 215,000 km. I have to be fair and say that the engine itself hasn't had any problems so far, which is why parts needed to be replaced. In other words: components like the VP44 (fuel injection pump), turbocharger, camshaft, etc., are still original and therefore 19 years old with 350,000 km on them...

Valve timings were checked at two independent workshops.

The battery is actually quite old, a few days/years old. Maybe I should try filling up with regular diesel again and see if bridging the terminals helps.

Hi there,

Quote:

The valve timings were checked by two independent workshops.

We cannot assess the result.
The behavior – poor starting when the engine isn't too cold, accompanied by white smoke, but better starting in colder environments (with preheating), and verschandeln starting with a more responsive premium diesel – already suggests a bad adjustment. However, without a description of how it was done, a Screenshot of the dynamic setting, and possibly a readout of the measurement blocks, we won't be able to do anything here.
hg
Herbert.

I just spoke with my authorized service center again, and they told me that the valve timing was reset two years ago during the timing belt replacement.

Lack of compression, a faulty VP44 pump, or defective injectors can be ruled out, because if that were the case, the car would also have difficulty starting with premium diesel.

Somehow, I'm currently stuck in a dead end .