Lupo 3L AYZ geht aus - Ideensammlung gezielte Fehlersuche | Posts 16+

Hello,

The bypass method will initially get the car running. Nevertheless, the question remains: how do I proceed?

Could it be that the diesel filter is causing this problem? Could the tandem pump be the culprit?

What problems can be expected if the filter preheating system is disabled?

Bye.
peace

pax wrote:

Hello, The bypass method will initially get the car running. Nevertheless, the question remains: how do I proceed? Could it be that the diesel filter is causing this problem? Could the tandem pump be the culprit? What problems can be expected if the filter preheating system is disabled? Bye. pax

In the summer, nothing happens. In the winter, the diesel engine *can* experience "flaking" (a type of fuel system issue).
It is well known that the snapping turtle inhales air.

Quote:

The bypass method initially causes the car to run. Nevertheless, the question is, how do I proceed?

If that's the case (fuel being directly returned to the tank) and the car is running, what's left to consider?

Instead of continuing to search endlessly, I would replace the water pump and filter.

Hello,

The water pump, including the gaskets, is new (installed this past Saturday), and in addition to the standard clamps, I've also added hose clamps to the hoses. The valve can also be installed with a similar level of tightness, just like in the older filters.

Only the new filter itself (about 3 weeks old) was temporarily swapped with the old one during troubleshooting, but only when the diesel was warm enough that the problem didn't occur. Now there's a MANN filter installed, and next I would try a Bosch filter. Are there manufacturers that are known to be ones you should avoid?

T3Surfer wrote:

In the winter, diesel fuel CAN form flakes

. Okay, as long as the PD elements aren't unhappy because of a longer period of colder fuel, it wouldn't be a problem right now.

Herbert wrote:

Is that 60°C? Is that normal for PD?

I've been thinking about that again. Maybe it's related to the fact that the 1.2L TDI doesn't have a pre-lift pump in the tank. The 1.4L TDI has one, and its "Knackfrosch" version also has a 30°C setting.

"If I want to permanently install a section of transparent tubing in the fuel line after this experience, what would be suitable? Currently, I have a piece of aquarium tubing connected to a plastic hose connector, which I consider to be not very durable. Brass hose connectors would certainly be okay. However, so far I haven't been able to find any transparent fuel hose that is rated for -30°C to approximately 120°C." Is there anything available on the market?

Bye.
peace

pax wrote:

If I want to permanently have a piece of transparent tubing in the inlet after the experience, what would be suitable? Currently, a piece of aquarium tubing with a plastic hose connector is installed, which I consider to be not very durable. Brass hose connectors would certainly be okay? However, so far I have not been able to find any transparent fuel hose for -30°C to approximately 120°C.

Based on my experience, aquarium tubing in the inlet and outlet between the Difi and the antler on the engine block is more robust than one might think: I have been using this stuff for years without noticeable problems.
In the first few weeks, it becomes noticeably harder, but the remaining elasticity seems sufficient to accommodate all the movements of the block.

Quote:

I've been using this stuff for years without experiencing any noticeable problems. In the first few weeks, it hardens significantly, but the remaining elasticity seems to be sufficient to accommodate all movements of the block.

.............., but this may not necessarily be the case for all aquarium hoses.

I think it's safer to get a piece of hose from a junkyard if necessary.

According to SSP223 regarding the 3-cylinder direct-injection engines, the 60°C setting is intended to concentrate heat within the engine during winter, thereby allowing it to reach operating temperature more quickly.

I've already had two sets of new, genuine replacement fuel pumps that were leaking. Similarly, I've also had three filters that had hairline cracks. This may not be immediately noticeable from the outside, but if a pre-pump isn't generating pressure, air will be drawn in.
The leaks in the filters were usually located at the soldered joints of the hose connections or at the attachment point of the "Knackfrosch" (a specific component). With soapy water and compressed air, it was easy to see.
You should also carefully inspect the drain valve and the rubber ring, as they are also made of plastic and can be a source of errors, potentially allowing air to be sucked into the system.

So far, I haven't had any problems with filters from the brands Bosch, Mann, and UFI.

Regards, Mpire.

P.S. The older VEP-Tdi models originally came with transparent plastic hoses from the factory. My 1Z in my Audi 80 had those, so maybe you can find something like that at a junkyard. It would be a durable option.

ulf wrote:

pax wrote: If I want to permanently have a piece of transparent tubing in the intake line after this experience, what would be suitable? Currently, a piece of aquarium tubing with a plastic hose connector is installed, which I consider to be not very durable. Brass hose connectors would certainly be okay? However, I haven't been able to find any transparent fuel hose for -30°C to approximately 120°C so far. Based on my experience, aquarium tubing in the inflow and outflow lines between the Difi and the antler on the engine block is more robust than one might think: I've been using this stuff for years without noticeable problems. In the first few weeks, it hardens significantly, but the remaining elasticity seems to be sufficient to accommodate all movements of the block.

"The same applies to my T3. Even before the engine conversion, I had a similar aquarium hose installed, and it worked perfectly with standard hose clamps. It's been in there for about 10 years." It's cured like Ulf's, and the other transparent originals are also quite hard.

Mpire wrote:

P.S. The older VEP-Tdi models originally came with transparent plastic hoses from the factory; my 1Z in the Audi 80 had those, so maybe you can find something like that at a junkyard; it would then be durable.

The problem is only:
As far as I know, these are thin, flexible tubes with multiple bends, and they are made with transparent sections. At the ends, they are fitted with elastic black pieces that are slipped over the actual sleeves. Therefore, there is very little room for cuts.

Therefore, I consider it highly unlikely to find a VEP part that would randomly fit into the sleeve space of another motor in a different car.

If you happen to find something suitable, the next question is whether the thin, transparent hose might restrict the diesel flow in the PD-ZK (positive displacement fuel pump) to such an extent that new problems arise (e.g., insufficient heat dissipation via the diesel).

Hello,

Last night, I replaced the supposedly new male connector with a new Bosch filter. On the first start, I left the "Knackfrosch" bypass in place, and after no more bubbles appeared, I properly installed the new "Knackfrosch" as well.

The mini-blaster's idle speed has now decreased slightly, and the foaming, especially at higher RPMs, has been significantly reduced.

On the way home from the garage (approximately 25km), there were no problems, but upon arrival, the odometer showed 2.9 liters per 100km .

Thank you very much to everyone.

Bye.
peace

pax wrote:

The mini-bubbles in the exhaust at idle have now decreased even further, and the foaminess at higher RPMs is noticeably reduced.

Hmm, I would still be a bit skeptical if I compare it to my own BUK: because there are absolutely no bubbles there, even at idle. I don't know about higher speeds.
I have only seen foam once, on a winter day when the temperature was somewhere below -10°C. At that time, the differential pressure (DiFi) was likely blocked, and the suction pressure of the tandem pump caused steam bubbles to form in the supply line. To match, the foam disappeared completely as soon as I turned off the engine.

Hi,
The transparent fuel lines, for example, in the 1Z model, are made of Polyamide PA12 (Polylauryl Lactan, melting point 178°C). I recently easily formed a 180-degree bend with a radius of 4cm on an old part using a heat gun at 190°C. At the very least, a similar setup should be configurable for that specific use case.
I wouldn't go too high with the temperature, because otherwise the PA12 might melt too much and not bend, but rather break.
I used to have a post here about the dimensions of the rubber connectors, which might also be helpful.
I will also try removing and attaching the PA12 pipes to the hose fittings at some point.
hg
Herbert.

Edit: Here's the post about the hoses: /viewtopic.php?t=22902

Herbert wrote:

The transparent fuel lines, for example, in the 1Z model, are made of Polyamide PA12 (Polylauryl Lactan, melting point 178°C). I recently easily formed a 180-degree bend with a radius of 4cm on an old part using a heat gun at 190°C. At the very least, a similar pipeline should be configurable for that use case.

Wow, that sounds encouraging at first!
I would simply take a complete part, for example from a 1Z model (PA12 material with black ends), and using a hot air gun, roughly bend it to fit in the PD-TDI engine bay. Then, I would mount it and, finally, use the hot air gun again to soften it so that it sits without any stress or tension.
What that probably doesn't refer to is... The throttle problem is solved if the PA12 part for the PD-TDIs is undersized.

There are two different types of pipes: a larger diameter pipe for the supply line (with a diameter of 6-7 mm internally), and a smaller diameter pipe for the return line.

Herbert wrote:

There are two different types of pipes: a large cross-section for the supply line (with a diameter of 6-7 mm), and a smaller cross-section for the return line.

Okay, the larger diameter might correspond to the PD hoses. You should then take 2 of those if you want to monitor both the inflow and outflow.
If the foaming only occurs during the intake stroke, then components such as the piston ring seals on the combustion chamber side could be suspected.

Hello,

He ran the :-)100km to work and another 100km back today, and it worked perfectly. Next time I visit the junkyard, I'll see what kind of parts are available.

Bye.
peace