Polo 9N3 (1,4l TDI PD) springt schlecht an, nach Standzeit | Posts 32+

DieselBär30x wrote:

Hi Stolli! As you correctly pointed out, this is merely a recommendation. The further the check valve is located upstream of the tank in the supply line, the more potential sources of error related to the piping will be "compensated for." On the other hand, I see a risk that by messing with the cables and such in this already very cramped space, we might introduce even more air leaks. Therefore, install the valve (the right way up!, of course) near the injection nozzle in the engine compartment and continue to observe. In most cases, this should resolve the problem. Best regards from Munich!

Hello Bear!

Okay, I think I'll do that and let you know how it goes! I'm curious to see if it works!

Greetings from the car, heading to Munich!

I have now installed the check valve in the supply line (before the diesel filter).

Unfortunately, it didn't achieve anything.
He still tends to be difficult to start after being driven for about half a day, requiring 8 to 10 hours to restart.

Does anyone else have any suggestions?

Have you ever tried logging the engine speed during a problem start? I quickly browsed through the topic, but couldn't find anything about it.

Best regards, Rainer.

Hi there,
Since the problem seems to be related to the fuel level in the tank... Is the tank ventilation working properly? As a test, try opening the gas cap after parking the car, thereby equalizing any potential vacuum and see if the problem disappears.

Best regards from Berlin.
olli

If the pressure sensors between the inlet and outlet are leaking, the fluid will simply flow back into the tank through the return line. And as far as I recall, the return line doesn't enter the tank at its highest point, but rather into the fuel unit. When the tank is full, for example, there would be enough resistance from the fuel level to prevent any backflow.

Personally, I wouldn't hesitate to continue using the PDs, even with their high mileage.

Autoservice wrote:

If the PDs (pressure diaphragms) between the inlet and outlet are leaking, then the fluid will flow back into the tank through the return line. And as far as I recall, the return line doesn't empty into the highest point of the tank, but rather into the fuel unit. With a full tank, for example, there would be enough resistance from the fuel level to prevent any backflow.................... Personally, I would have absolutely no qualms about continuing with the PDs regarding the mileage.......

Hi!

That makes sense!
Considering the effort involved (buying special tools, adjustments, etc.), I'm already having second thoughts about removing the catalytic converters.

I'd rather put up with the poor starting behavior. Or am I causing further damage by doing so?

Look at this: https://community.dieselschrauber.org/en/viewtopic.php?t=5408

It's not that complicated. The key to adjusting it is actually just finding the deepest point where the camshaft or eccentric shaft engages with the timing mechanism.

Autoservice wrote:

Look at this: https://community.dieselschrauber.org/en/viewtopic.php?t=5408 It's not that complicated. The key to setting the timing is actually just finding the deepest position that the camshaft or eccentric shaft applies pressure to the pivot point.

Thanks for the link; it seems like the setup isn't as complicated as I thought!
However, to expand it, I would need a suitable puller and mounting sleeves for the seals, right?

Quote:

However, to expand it, I would need a suitable puller and mounting sleeves for the seals, right?

Theoretically, yes, but it can also be done without them. If the tensioning blocks are removed, spray a generous amount of WD-40 or similar into the shaft. Usually, the pressure dividers (PDs) have some play in their guides, which allows them to be carefully levered out. When installing the sealing rings, make sure they are not damaged and are not twisted during assembly. If necessary, you can also use thin adhesive tape as a replacement for the mounting sleeves. When inserting the PDs into the shaft, ensure cleanliness and that everything moves smoothly so that you don't damage the sealing rings during insertion.

Autoservice wrote:

If the PDs (pressure diaphragms) between the inlet and outlet are leaking, then the fluid will flow back into the tank through the return line. And as far as I recall, the return line doesn't enter the tank at its highest point, but rather into the fuel unit. With a full tank, for example, there would be enough resistance from the fuel level to prevent any backflow.................... Personally, I would have absolutely no qualms about continuing with the PDs regarding the mileage.......

I need to revisit the solution for lazy guys:
Wouldn't it also be possible to install a check valve in the return line to prevent the broth from flowing back?

And: Are you talking about a leak in the PD units themselves? In that case, I would need to have them rebuilt, right? Because replacing the seals on the PD seat wouldn't solve the problem...?

Hi Stolli!

The check valve in the return line isn't working.
Here's the translation:

"Explained logically: When the system is running, leaked oil flows towards the tank, so there must be a continuous path in that direction. However, a valve in the flow direction won't help because when the system is idle, the path remains the same."
If so, then there would have to be a solenoid valve installed that closes when the ignition is OFF... but I'd better leave it alone, because that would already be a workaround for a workaround .

Regarding PDEs:
Die wären nicht selbst undicht sondern die Abdichtungen zw. PDEs and ZK.
As mentioned before, the only solution is to expand and investigate further!
If there are significant or sharp grooves formed in the pump drive shaft (PDS) housing, you would need a new PDS assembly because it will be difficult to achieve a proper seal even with new sealing rings.

Therefore: The "lazy boys" theme has unfortunately died due to the installed check valve.

Best regards from Munich!

DieselBär30x wrote:

Hi Stolli! The check valve in the return line isn't working. Here's the translation: "Explained logically: When the system is running, leaked oil flows towards the tank, so there must be a continuous path in that direction. However, a valve in the flow direction won't help because when the system is idle, the path remains the same." If so, then a solenoid valve would need to be installed that closes when the ignition is OFF... but I'd rather not do that, because that would be a workaround for a previous workaround.

Hello Bear!
Awkward, I could have figured that out myself!

DieselBär30x wrote:

Regarding PDEs: Die wären nicht selbst undicht sondern die Abdichtungen zw. PDEs and ZK. As mentioned before, the only solution is to expand and investigate further! If there are significant or sharp grooves formed in the pump drive shaft (PDS) housing, you would need a new PDS assembly because it will be difficult to achieve a proper seal even with new sealing rings. Therefore: The "lazy boys" theme has unfortunately died due to the installed check valve. Best regards from Munich!

Okay, I'll plan to tackle this project during the gloomy autumn months and hope that the timing chain is still in good condition. If not, at a current mileage of 292,000 km, it probably wouldn't be worth doing anymore...

Best regards from Freimann!

Autoservice wrote:

If the PDs (pressure diaphragms) between the inlet and outlet are leaking, then the fluid will flow back into the tank through the return line. And as far as I recall, the return line doesn't enter the tank at its highest point, but rather into the fuel unit. With a full tank, for example, there would be enough resistance from the fuel level to prevent any backflow.................... Personally, I would have absolutely no qualms about continuing with the PDs regarding the mileage.......

Hello Uncle!

Regarding this matter, I have one more question.
Could a leak between the tandem pump and the timing chain tensioner also be a cause of these symptoms? In my small 3-cylinder engine, it's slightly leaking there as well. I already replaced the seal once, but that job is simply hell because of the tight space!

I just want to rule out the possibility of having to replace the PD seals (are seal kits from eBay or a supplier recommended?) even though the tandem pump is leaking.

Quote:

Could a leak between the tandem pump and the injection cylinder also be a possibility with these symptoms?

"You can never completely rule it out. But... if you want to find a solution, you have to start somewhere. Unfortunately, that's the situation when a standard search (e.g., checking Difi, Knackfrosch if available, fuel lines, etc.) doesn't yield any results."

As I mentioned before, in the recent cases that I am aware of, the power drives were leaking.

Autoservice wrote:

As I have already written, in the last cases that I am aware of, the PDs were leaking.

Okay, I'm still thinking about which job is the less unpleasant one...!

Supplier-provided specifications should be acceptable as well, right?

Autoservice wrote:

Look at this: https://community.dieselschrauber.org/en/viewtopic.php?t=5408 It's not that complicated. The key to setting the timing is actually just finding the deepest position that the camshaft or eccentric shaft applies pressure to the pivot point.

Regarding this, I have two more questions.

Should I log any values in VCDS before and after adjusting the piezo injectors to verify their correct settings?

And: how would I know if the PDE (pre-detonation) has already started occurring? Or is that not something to worry about with this engine?

Best regards,