TDI AFN: Quantity Solenoid Upper Stop - Explained

Evening, guys.

Despite having read the relevant forum posts and articles, I still have a question:

Am I correct in assuming that the error is...?

Upper limit setting.

Can the VP37 error code only occur due to a faulty or stuck quantity control valve, as is usually stated? Or can the control unit also generate this error in other situations?

The fuel pump was adjusted with a gauge after the timing chain replacement (engine overhaul!), and the starting behavior and idle speed are fine.

However, there is a lack of performance and this error in the system.

I suspect the fuel quantity adjuster might be stuck because the engine has been on a pallet (not with me...) for at least a year and a half. My next step is to run a bottle of Liqui-Moly diesel cleaner through the pump, with both inlet and outlet lines connected to a separate container.

Any other brilliant ideas?

Hi,

It could also be due to the position (setting) of the point machine.

Basically, it could be anything that prevents the pump from reaching its upper limit (e.g., wiring harness, flow meter) or that alters the feedback signal accordingly (e.g., wiring harness, potentiometer, or HDK sensor, such as water or debris in the ESP system).

Best regards, Rainer.

Can I bleed the pump by disconnecting the central screw in the middle of the four injector lines on the distributor block while the engine is running? Is this advisable, and what's the best way to do it?

If the error is caused by a blockage due to debris, what is the likelihood that I will see something if I disassemble the metering unit from the pump after marking its position?

Am I correct in thinking that I could try shifting the quantity adjuster a few 1/10mm towards the distributor body, or was it exactly the other way around?

Hi,

Quote:

Can I bleed the pump by using the central screw in the middle of the 4 injector lines on the distributor block while it's running? Is that advisable, and what's the best way to do it?

In the correct position, yes. I would simply apply strong suction at the return line.

Quote:

If the error is caused by a blockage due to debris, what is the likelihood that I will see something if I disassemble the metering unit after marking the position relative to the pump?

Most likely. However, please check the plug/cable, etc. connected to the pump beforehand and note the values for the lower and upper limits.

Quote:

Am I correct in thinking that I could try shifting the quantity adjuster a few 1/10mm towards the distribution body, or was it actually the other way around?

"Good question. To answer that, we'd need to examine how the mechanical stop is configured; I don't know the answer off the top of my head. Theoretically, a shift to the right (towards the cables) should reduce the voltage reading from the upper limit."

Best regards, Rainer.

Hmm, so I bought some "Atomspritze Leningrad" and took a few hundred milliliters.

The connectors have been checked, as well as the continuity/resistance to the control unit; everything is okay.
Similarly, the resistance and continuity values of the electronic pump components must comply with the specifications of the relevant VAG-RLF standards.

Hi,
By adjusting the potentiometer, I don't think anything can be achieved. The current flowing through the potentiometer and the signal from the RSW sensor should remain unchanged, as only the deflection of the potentiometer ring changes.
If nothing seems to be stuck, perhaps recalibrating the RSW sensor might help. As far as I can tell, during the test, after turning on the ignition, the minimum/maximum value of the quantity setting is reached, and the feedback from the sensor is checked.
The target ranges for the voltage of the RSW sensor are known.
hg
Herbert.

Hello,

Quote:

I don't think anything can be achieved by moving the potentiometer. The current through the potentiometer and the signal from the RSW sensor should remain unchanged, as only the deflection of the potentiometer ring changes.

I thought so too. However, I seem to recall that the start-stop values may have shifted. Unfortunately, I don't have a pump that I can disassemble and inspect.

What are the start-stop values?

Best regards, Rainer.

I am referring to my 1Z. According to the manual, the MWB 19 should provide a voltage of 0.6 - 0.9 V at the bottom and 3.8 - 4.4 volts at the top when ignition is on. If it's outside of this range, either the transition resistances or the MSW (measurement system) are likely misadjusted, according to the manual.
I can't check it on my car, as my control unit doesn't yet provide diagnostic data ID 19.
(I didn't intend to move the measuring device anyway ).
Looking at the two technical articles (cleaning the MSW, disassembling the high-pressure section), it seems like the shifting process shouldn't have any effect. In my opinion, the mechanics of the MSW also remain unchanged.
hg
Herbert.

Okay, thank you for the feedback!

Since it appears that the upper limit will not be reached, the following measures will now be implemented:

1. Liqui-Moly Flush.
2. Optical "span test".

I will report!

The flushing process was unsuccessful, so we will now proceed with checking the "mechanics."

Hi,
Perhaps fill the ESP reservoir again with LM, remove the lid of the ESP, and carefully move the quantity adjuster and, with it, the quantity adjuster ring, back and forth by hand. The quantity adjuster ring may be stuck. At the very least, this method allows you to check the mechanics without adjusting anything.
hg
Herbert.

You mean I can manually rotate the potentiometer shaft from stop to stop and then reinsert it?

Deus Violentia wrote:

You mean I can manually rotate the knob of the potentiometer from stop to stop and then reinsert it?

Yes, it should normally be easy to do.

Hi,
You don't need anything other than the MSW cover to remove and reinstall it. Simply adjust the quantity setting by hand, feeling for the correct position as you rotate the sensor on the shaft after removing the cover.
hg
Herbert.

edit: just for safety - before and after removing the cover, with the ignition on, note the value 3 (voltage of the RSW sensor) from MWB 1. If the holding screw and sensor unexpectedly come loose, you will have a reference for adjustment. See the instructions for cleaning the MSW.

I will definitely try that! Thank you for the tip!

Okay, so yesterday I went all out.

Intake manifolds, injectors, and turbochargers:

Cleaned the intake manifold, disassembled the VNT15 turbocharger and completely cleaned the VTG (Variable Turbine Geometry), and resealed the fuel injectors with new copper rings (because there was something strange about the seating in the cylinder head, and I wasn't sure if someone had removed them before without replacing the rings).

VP37 quantity adjuster

I removed the cover of the VP37 and manually adjusted the setting.
Result: No sticking, consistent spring force from left to right, and a firm seal. So, I installed a new Bosch seal in the cap, closed it again, and filled it with diesel using a syringe.

Vacuum sensor VTG

Then I noticed something else that I hadn't seen before: The vacuum chamber, for some reason!, is bent and doesn't extend all the way to the adjustable stop . However, the test with the syringe showed that it still regulates "somewhat" smoothly, but it tends to stick rather than reaching the stop. So, a new vacuum chamber will be needed.

I also noticed that some kind of vandal probably moved something, because the yellow sealing wax on the screws at the bottom of the signaling device is missing, meaning the screws were exposed.

Rainer du schriebst, daß der Fehler "Mengensteller oberer Anschlag" eben auch daher kommen kann, ich schätze daß der Mengensteller axial Richtung HD-Teil verschoben wurde. WäIs that plausible?

Regarding the starting behavior and current driving characteristics:

The cold start went smoothly after the assembly; a slightly longer idling period (1 minute) was necessary because I had the nozzle bodies removed and the pump was open.
Since I had, following Ulf's advice in the technical article about the VP37 adjustment, re-supplied it with diesel using a syringe through the inlet side after mounting the cover, until diesel came out of the return side, everything was very straightforward.

Warmstart

Unfortunately, I didn't have a VAG-Com diagnostic tool available... The idle speed is stable, the engine starts perfectly when warm; it just needs to be left running for a second before it runs smoothly.
The performance is significantly better than before, but it's still not an AFN (Advanced Fuel-efficient Natural Gas engine), more like a 1Z (a different engine type).

After working for 15 hours today, I was tempted to mess with the pump at 1 AM and see what you all think!

Thank you very much! [/b]