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

Hello,

The bypass method initially gets the car running, but the question remains: how do I proceed from here?

Could the diesel filter be 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, but the question remains: how do I proceed from here? Could the diesel filter be 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 issues like fuel gelling.
It is well known that the "Knackfrosch" (a type of frog) inhales air.

Quote:

The bypass method initially gets the car running.

However, the question remains: how do I proceed from here?

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

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

Hello,

The new water pump (including the O-rings) is brand 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 tight fit as in the old filter.

Only the new filter itself (about 3 weeks old) was initially 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 Bosch. Are there any manufacturers that are known to be problematic?

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, that wouldn't be a problem right now.

Herbert wrote:

Only at 60°? 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 does, and its "Knackfrosch" (presumably a component) is also a 30°C version.

"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, I haven't been able to find any transparent fuel hose that is rated for -30°C to 120°C. Is there anything like that 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 haven't 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've been using this stuff for years without any 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 becomes significantly harder, but the remaining elasticity seems sufficient to accommodate all movements of the block.

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

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

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

"I've already had two new, genuine replacement fuel pumps that were leaking. Similarly, I've also had three filters that had hairline cracks. This isn't always noticeable externally, especially if there's no pre-pump generating pressure, as it allows air to be drawn in."
The leaks in the filters were usually located at the soldered joints of the hose connections or the "Knackfrosch" (a specific type of fitting). You could easily see them by using soapy water and compressed air.
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, so far I haven't 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've been using this stuff for years without noticeable problems. In the first few weeks, it becomes significantly harder, but the remaining elasticity seems to be sufficient to accommodate all movements of the block.

"My T3 is the same; I had that aquarium hose installed even before the engine conversion, and it worked perfectly. It's held in place with standard, everyday hose clamps. It's about 10 years old now. Like Ulf mentioned, it's become quite hard, and the other clear, original hoses are also quite rigid."

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:
To the best of my knowledge, these are thin, multi-bend form tubes made of transparent material, and they are finished with elastic black pieces at the ends that are pushed onto the actual nozzles. Therefore, there is very little room for shortening them.

Therefore, I consider it highly unlikely to find a VEP part that would randomly fit into the space intended for a strut in a different engine of 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,

Yesterday evening, I replaced the supposedly new male connector with a new Bosch filter. During the initial start, I left the "Knackfrosch" bypass in place, and after the bubbles stopped, I properly installed the new "Knackfrosch" connector.

The mini-blast phenomenon at idle has now decreased further, and the foaming, especially at higher speeds, has been significantly reduced.

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

Thank you very much to everyone.

Bye.
peace

pax wrote:

The mini-bubble formation at idle has now decreased even further, and the foaminess at higher RPMs is noticeably reduced.

Hmm, I would still be somewhat skeptical if I compare it to my own BUK: because there are absolutely no bubbles there, at least at idle. I don't know about higher RPMs.
I have only observed foam once, on a winter day with temperatures somewhere below -10°C. It's likely that the differential pressure sensor was malfunctioning, and the suction pressure of the tandem pump caused steam bubbles to form in the supply hose. Correspondingly, 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 Lactam, melting point 178°C). I recently easily formed a 180-degree bend with a radius of 4cm on an old part using a hot air gun at 190°C. Therefore, a similar line should be able to be manufactured for the intended application.
I wouldn't set the temperature too high, 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 olives at some point.
hg
Herbert.

Edit: Here's the post about the hoses: https://community.dieselschrauber.org/en/viewtopic.php?t=22902

Herbert wrote:

The transparent fuel lines, for example, in the 1Z model, are made of Polyamide PA12 (Polylauryl Lactan, melting temperature 178 °C). I just easily formed a 180-degree bend with a radius of 4 cm on an old part using a hot air gun at 190°C. At least, a similar line should be able to be manufactured for the intended application.

Wow, that sounds quite encouraging at first!
I would simply take a complete part, for example from a 1Z model (PA12 plastic with black ends), and using a heat gun, roughly bend it to fit in the PD-TDI engine bay. Then, I would mount it and, finally, use the heat gun again to soften it so that it sits without any stress or tension.
However, this does not necessarily solve the potential issue of the throttle, if the PA12 part were undersized for the PD-TDIs .

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

Herbert wrote:

There are two different types of pipes: a large diameter for the supply line (with an inner diameter of 6-7 mm), and a smaller diameter 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 supply and return lines.
If foaming only occurs during the return stroke, then components such as the piston ring seals on the combustion chamber side might 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 hoses I can find.

Bye.
peace