T5 2.5 BNZ - Bleed fuel filter; VCDS issue

A friendly hello to everyone,

Our T5 just had its 120,000 km service, which included a fuel filter replacement.

On this occasion, we also replaced the gasket between the turbocharger and the engine block (due to significant oil leakage) and the gasket between the exhaust manifold and the turbocharger (due to a strong exhaust smell inside the car when idling).

So far, so good: Now we wanted to bleed the diesel filter, but we're encountering some problems.

There are issues with VCDS (using the latest version 12.12 as well as the older version 11.5). The wrong label file is being loaded for the measurement data blocks (not the one for BNZ, but the one for BCP).

In the actuator diagnosis, the "Selective Actuator Diagnosis" option is grayed out. In the standard actuator diagnosis, the fuel pump is also not activated.

Switching to the default setting (as described, for example, in the VCDS forum) using MWB035 also doesn't work, because the "default setting" field is also inactive.

Is there a way to manually control the coolant pump (KST-Pumpe) using VCDS on a BNZ engine?

2: Which of the relays located at the front of the engine compartment is the fuel pump relay?
Would that simply bypass the issue and let the pump run for 2 minutes?

Hello,

Please upload the Autoscan data. The fuel pump automatically starts when the ignition is turned on. Turning the ignition on and off a few times might solve your problem.

Best regards, Rainer.
PS: According to our customer database, you do not have a VCDS license.

Hello Rainer,

I have turned the ignition on and off approximately 20 times. The engine started immediately, but after about 10 seconds, it began to sputter and then stalled.

I purchased the complete VCDS system from you last year/the year before, and I can also download the current version 12 from "My Account."

Autoscan will follow.

Okay, I see there's a second one. Customer account with a different email address than the one used here.

In the "About..." dialog, in addition to the version number, there is also the data status, which is particularly relevant for the labels. The data status, also known as the Autoscan, displays information such as label files, the part number of the respective control unit, its software version, and its coding.

Best regards, Rainer.

Okay. I'll do the car scan tomorrow after work and upload it then.

Is there a way to activate the fuel pump using the diagnostic system?

Attached is the Autoscan!

Yesterday, I bypassed the fuel pump relay and let the fuel pump run for about 5 minutes. However, it didn't help; the engine still won't start, so there seems to be a lot of air still in the fuel line leading to the common rail injectors.

Does anyone know of any other tricks to completely bleed this system?

Quote:

Does anyone know of any other tricks to get rid of all the air in this thing?

Using a vacuum pump, draw fuel through the return line (from the fuel pump) until diesel starts to flow. While doing this, close the open fitting on the filter. You can potentially cut off the fitting from the old filter and use it as an adapter for the hose connection. Don't forget to deburr/clean.

If a vacuum pump is not available, or if you have to carry it, use a transparent tube so you can see when it arrives .

After the car had been standing overnight, I tried again the next day. Ignition on/off ten times, and lo and behold, it started.

The bus is running again. "Still, thank you to 'Autoservice' for the tip."

However, I can't understand why, after approximately 5 minutes of the fuel pump running, the system wasn't bled and the engine didn't even try to start. To my knowledge, with the guided diagnosis, the pump is only activated for "just" 70 seconds, and supposedly that is sufficient.

It would also be interesting to know why the ventilation system isn't working with the MWB035 (the option to switch to the default setting is grayed out and unavailable).

Does that generally no longer work with newer engine control units?

Did you pre-fill the filter with fuel before installation, or did you install it "dry"?

Thank you for the feedback .

Quote:

Despite this, I cannot understand why, after approximately 5 minutes of the fuel pump running, the system was not bled and the engine did not even try to start.

I think you may have drained the small circuit between the Difi and the motor "before" bleeding it using the KR pump, and that the KR pump didn't provide sufficient flushing to reach the PDs (presumably referring to pressure distribution devices).

Next time, "before" starting the engine, make sure to properly bleed the system .

@ MatthiasTDI96

The filter was installed in a dry condition.

@ Autoservice:

After installing the new filter, and since the issue with MWB035 hadn't been resolved, I switched the ignition on and off approximately 20 times before starting the engine for the first time. Then I started the engine.

There is another mechanical injection pump located on the engine, which pumps the diesel fuel into the injection distributor and then to the common rail injectors.
Could it be that the electric pre-feed pump is having trouble pumping the coolant through, and as a result, air is not being pushed out through the return line? Then the official venting method (70 seconds of the electric pump running) would also be pointless.

Then I think that it was made more difficult by the lack of, or limited use of, [something].