Injection Start Timing V6 TDI AKN

Hello!

About the vehicle:

Audi A6 V6 TDI Quattro, year 2000, engine code AKN, manual transmission.
Mileage: 75,000 km.

In the past, there have occasionally been minor power interruptions or temporary performance drops during strong acceleration.

After replacing the filter and then taking the vehicle for a test drive, the engine suddenly started running with a fluctuating idle. The problem occurred at medium RPM and partial load. It seemed like air was being drawn into the system through the pump (producing a loud ticking sound).

Now, the engine is only running at approximately 450 RPM, fluctuating in a limp mode. The combustion is incomplete and sounds very soft.

Absolutely no gas intake.

Das VAG Diagnosegerät zeigt dabei an: Spritzbeginn 7-8° n. OT.
Error: Injection start control - difference between setpoint and actual value.

The fuel supply was already implemented using a canister without any modifications.

Das Druckregelventil wurde kontrolliert. It is common.
The filter underneath is free of contamination.

Does this pattern of damage look familiar to you?

I have several VP44 units of unknown origin/history available, and I might be able to use them as donor parts.

Currently, we are checking to see if the belt drive is functioning correctly and is properly adjusted. However, I fear that may not be enough.

Best regards, Tom.

Hello,

Let's read the data from measurement block 4 while the engine is idling (paying attention to the operating conditions) and then post the results. This will help us narrow down the problem.

'I had similar problems with my Passat V6 TDI, engine code AFB, with 106,000 km on the clock. The workshop diagnosed a faulty fuel injection pump. I was able to buy a new VP44 pump cheaply on eBay, had it installed, and that solved the problems. I suspect that the seals in the pump are defective due to the use of a mixture of mineral diesel and biodiesel. I will have the replaced pump checked again for this issue at some point.'

Deleted upon request.

Hello!

Thank you for your responses.

After disassembling the VP44 pump and identifying a fault in the injection start control, I now know more.

First, a likely long-standing issue with the injection timing adjuster piston probably caused the frequent emergency running that occurred in the past. The cylinder liner shows signs of wear on the top.

The complete failure occurred again, contrary to all predictions, due to the failure of the IWZ system. The retaining ring of the rotary angle sensor is synchronized with a bolt in the rotating cam ring via a fork. A tooth broke off the fork, which is machined from a solid piece on the retaining ring, causing the rotary angle sensor to become completely decoupled from the cam ring. The bolt in the cam ring could no longer move the rotary angle sensor; it moved almost randomly during operation. Consequently, the measurement value from measurement block 4 was also unusable.
The engine was last running at 450 RPM with a severely delayed injection timing and producing a lot of smoke.

After installing a replacement pump, the vehicle is, of course, running again to the complete satisfaction of the customer.

If needed, I can send you pictures of the defective pump/parts via email.