TDI engine suddenly starts very poorly. Why?

Hi,
I'm having the following problem: For the past year and a half, I've been using biodiesel in my 1Z-TDI, and I've never had any problems with it until now. Three months ago, I proactively replaced the diesel filter.
And now, serious starting problems! I admit, it wasn't sudden; over the past few days, it's been starting with a strange noise and hesitating for the first few seconds. Something else that just occurred to me is that he also had a poor start in the first 100 meters.
Anyway, it's only been starting for the past two days when I crank the starter for a looooong time, even though it used to start after just one rotation.
The fuel seems to be being fed and injected, as it's smoking, and eventually, after a long cranking period, it starts. Warm start is not a problem at all; it starts up immediately.
Since I know that it starts poorly in the winter when using biodiesel, I switched to regular diesel, but that doesn't change anything at all.
Does anyone have any idea what might be causing this behavior?
Thank you and best regards,
Kisses.

P.S.: Surely, a bad compression wouldn't just happen, would it? It's more likely to creep in gradually rather than appear within a week.

1Z has had many different versions - including the year of manufacture, vehicle type, etc. (see also common mistakes).

Since you have an RME system, my immediate thought is that the seals inside the pump might have deteriorated, causing the pump to draw in air (overnight). This air then needs to be purged before the next (cold) start.

The next likely culprit would be the crankshaft bolt...

Search function rocks.

Best regards,
Rudi

Hi,

Okay, Passat 35i, manufactured in June 1996.

Seals in the pump? Probably the hose clamps on the pump, right?
Wouldn't the air bubbles be visible in the transparent tube?
What speaks against it: Yesterday afternoon, when it was over 30 degrees Celsius, it started more easily than this morning, when it was only 18 degrees. Strange, isn't it? Both times, he stayed overnight.
And also, it's emitting a lot of smoke, like it's injecting diesel.
It seems more like what happened when I replaced the timing belt and the pump wasn't properly aligned. He was smoking constantly, occasionally trying to start it, but then nothing would happen.
This morning, on the first turn, it immediately sparked, then nothing more. As the turning continued, more and more sparks occurred, until finally, it worked.

Why is the crankshaft bolt being considered?

Search function is nice and all, but I need the car every morning for work, and I don't have a second car, so I need a quick solution!

Regards,
Kisses.

P.S.: What's the deal with the 'Fettnäpfchen' thing?

I forgot something else.
What surprised me about the last vehicle inspection (ASU) was that he only just passed, even though biodiesel is known to produce 90% less soot.
I used to have a different 1Z that was so clean, you could almost breathe in the exhaust fumes!
Regards,
Kisses.

Could you please check the valve timing and the start of fuel injection?
Maybe you'll find what you're looking for there!
If the valve timing is incorrect, try searching for "crankshaft adjustment screw" in the search function.
then you know what is meant by that.

Hi,

Why would the valve timing have shifted? And as I described, the process was gradual, so it didn't happen overnight.
I was just looking at the ESP earlier and noticed some minor seepage points on the sealing surfaces. It might be related to some kind of deterioration of the seals. But if that's the case, what should I do? I do have a spare pump on hand, but it will eventually start leaking too.
But then I don't understand why the other one never had any problems with biodiesel and a 1Z engine.

Regards,
Kisses.

Here's a reminder: try searching for '1Z' and 'crankshaft bolt.'

That clarifies your question: a loose KW screw is a common issue.

Best regards,

Hi.

Everything can somehow be altered. Vibrations and aging are already two factors that can easily cause misalignment, especially in the 1Z model.

Why did my 23-month-old flexible pipe fail? I have no idea.

Check everything thoroughly, especially things that don't have anyone to advocate for them. Starting a business can really be a side hustle, it's that simple.

And for comparison with the other 1Z: All components are constantly being changed and adapted, etc.

Perhaps the other one simply had a more robust sealing ring.

m;

My condolences, dear colleague...

To me, it clearly looks like there's a leak in the ESP (Electronic Stability Program).
(I wouldn't want to put my hand in the fire for that, other causes are not ruled out...)

You're not the first person to experience problems after years of trouble-free refueling with biodiesel, only to suddenly encounter issues.
As Rudi already mentioned, the pump draws in air overnight, which needs to be pumped out during the cold start, hence the sputtering idle for the first few seconds.
Please review the following posts and reports; you will find that your issue is clearly reflected in one of them (1. Sure, here is the translation of the text from German to English:

'Link, below).'

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Here are a few testimonials from me.
(The first one is long, and therefore quite colorful, highlighting the keywords .)

Okay, I'm ready. Please provide the German text you want me to translate.

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Best regards, Georg.

Okay, I've just completed some initial investigations that go beyond subjective assessments, and I can now provide the following information:
1. Error codes read, no errors found. Nice!
2. Engine started, but I disconnected the coolant temperature sensor beforehand so it thought the engine was freezing cold. It pre-glowed for a very long time, cranked a few times, and almost started.
3. Injection timing was checked, and the following observations were made:
- The central screw was removed, and not a single drop of diesel fuel leaked out.
I'm not sure if this is normal, as it's been a long time since the last adjustment, but I think I vaguely remember something like this, and also, logically, it seems like there should be some diesel leakage if there's air in the ESP, right?
- The gauge was screwed in, set to the top dead center (TDC) position, and observed. Initially, the gauge didn't move at all (as it should rotate counter-clockwise), but then it suddenly started rotating in the opposite direction. This turning point was used as a reference. The gauge was then set to 'zero,' rotated forward again to the TDC position, and a reading of just under 0.95, or slightly more, was measured. According to my instructions, it should ideally be 0.70.

Does anyone have any idea why the value is so wrong, all of a sudden?

The central bolt on the crankshaft was obviously very tight, and the belt tension was also okay. The belt itself has only been driven for about 40,000 kilometers and seems to be okay.
Regards,
Kisses.

'0.7 would be correct for the first cylinder. Therefore, the timing is incorrect, and your difficulty starting is probably due to that. Here's a small tip: Search for 'Hähnlein's Mega Cold Start Thread.' You'll probably find that adjusting the injection start with a timing light is highly questionable, and that VW specifies adjusting the injection start dynamically.' Okay, freshly adjusted and working perfectly with VAG-COM!

Hmmm...
I recently adjusted it again using a measuring tool. The following...
A timing check could have been published.

Best regards,
Rudi

Hmmm...
I recently adjusted it again using a measuring tool. The following...
A timing check could have been published.

Best regards, Rudi

While this may be true for some units, please take a look at the thread I mentioned. That looks completely different!

I just recalibrated the pump, and it took me a long time. Either it was completely misaligned (why?), or I completely messed it up!
Anyway, after I bled the pump through the return line, it started up immediately and is running as before.
Now I'm curious to see if the ESP will work again tomorrow; if it does, that would mean the seals are gone!
And if that's the case, where are the new seals coming from (probably Bosch), and what is their quality (for biodiesel)?

That's all for today.
Best regards,
Kisses.

While this may be true for some units, please take a look at the thread mentioned. That looks completely different!

Hmmm... you're right. What happened to Christian there (or what he measured) .

However, the success of the whole thing also depends on how well the watch is adapted.
I'm lucky that I have access to a threaded extension (VW part number ???).


Best regards,
Rudi