VP 37: Can I diagnose a clogged diesel filter using VAGCOM?

Hello everyone

I was just thinking about whether VAGCOM can be used to identify fuel system bottlenecks.
Because the metering adjustment is based on the internal pressure of the pump, which is then "fine-tuned" by the metering adjuster.

If, however, the wing cell pump is throttled on the suction side due to a clogged filter or other issue (or if it draws in excessive amounts of air), it can no longer build up the normal internal pump pressure, and the spray adjustment will go out of control.
Thanks to the feedback loop, the engine computer should then try to compensate for the missing internal pressure by increasing the pressure (according to the VAGCOM) Adjusting the offset -> therefore, maximum initial adjustment.

Now, for example, my tractor shows an increase in the throttle ratio at the fuel control lever of approximately from 70 to 85% between 2000 and 3000 rpm, and only a minimal further increase to almost 90% between 3000 and 4000 rpm.

However, a clogged filter is first and mainly noticeable in the upper speed range, meaning that the ratio of the fuel mixture should be particularly noticeable there (compared to the normal state) with increasing speed.

Therefore, one could use a log of the injection adjustment, for example, during the DZR test, to control the filter - and perhaps even introduce "flexible diesel filter replacement intervals" privately, because the filters are not cheap

Has anyone ever observed something like this before, or can anyone confirm or refute my theory?

Hello Ulf,

I have read your filter theory, and it was also one of the starting points for my own thoughts.

Now I can tell you: If the resistance is already so high that bubbles form, or if the system starts to suck in air due to even the smallest leaks, the whole thing will quickly collapse. The fuel injection system is malfunctioning, the engine is sputtering and producing excessive smoke.


But another tip for your filter: Use a 2€ paper filter in front of the main filter. This will allow you to see if there is dirt in it, and you can really run the main filter for a very long time. Mine had 60,000 hours, and I only had to replace it because I had that problem. But I think it would still have been okay. By the way, I had to replace the paper filter 4 times during this period due to obvious contamination.

Best regards, Garth.

garth.brooks wrote:

Make a 2€ paper filter in front of the main filter.

Hi Garth,

This is a very good idea

garth.brooks wrote:

However, another tip for your filter: Use a 2€ paper filter in front of the main filter. This will allow you to see if there is dirt in the water, and you can really run the main filter for a very long time. Mine lasted 60,000 liters, and I only replaced it because I had this problem. But I think it would still have been okay. By the way, I had to change the paper filter 4 times during this period due to obvious contamination.

Hi Garth

I agree - good trick

I bought a larger filter from the hardware store specifically "for Audi + VW carburetor engines" before.
Before I use it: do these filters also filter out diesel, or do I have to rely on chemical decomposition?
Or, have you found a specific diesel pre-filter? If so: Manufacturer and type??

Would you, by any chance, object to incorporating this story into the "Tips + Tricks" section?

Hi Ulf,

regarding the filter's resistance, fuel = fuel.

Differences arise only in the filtering effect; diesel filters are much finer than those for gasoline engines. (Diesel better 5 microns)


For the small pre-filters, it really doesn't matter; they can even stop RME, and as you know, that stuff causes everything. (Does anyone want to know what it costs to seal a VP37 after 20,000 km with RME? And what is Audi willing to pay as a result of the approval? )

I'm trying to remove them because they seem to be a bit larger. Otherwise, I think it doesn't matter, as the purpose is just to remove the bulk of the dirt from the expensive diesel filter.

Use 2 clamps per side, due to the vacuum, it's 100% impossible to get a perfect seal, but at least you'll see that you've messed up here.

Greetings

garth.brooks wrote:

For the small pre-filters, it really doesn't matter; they can even stop RME (a type of dust), and as you know, dust is the culprit in everything. . . . Use 2 clamps per side, due to the vacuum, it's 100% impossible to get a perfect seal, but at least you'll see that you've messed up here.

Hi Garth

Okay, I'll just put that in.

Soon, your tip will be featured in the professional articles, okay?