A6 2.5 TDI: Won't Start? Troubleshooting Guide

Hello everyone,

My A6 4B with a 2.5 TDI 180hp engine (BAU code) won't start.
When trying to start the engine, it almost starts but doesn't quite make it. The engine speed when cranking is 250 RPM. Based on my feeling, I would say that the injection timing is likely incorrect.

Based on this suspicion, I replaced the timing belt, as it wasn't in the best condition anyway, and blocked the engine using the special tool required for the job. Unfortunately, this didn't solve the problem; the issue persists.

The pre-charge pump is working as it should and is providing 0.5 bar of pressure.
MWB 18 is only displaying zeros. The field to the right of it occasionally showed that one impulse was within the normal range and one was outside of it.

There is no air visible inside the clear tube.

However, if you start the engine with the initial settings in mode 4, and then try to start it, it will briefly start, run for a few seconds, and then shut off again. Otherwise, it only produces white/gray smoke. However, the injection timing always shows 0 degrees in mode 4.

"The pump control unit was already repaired by the previous owner about 2 years ago. I noticed that the insulation on the two cables leading to the lower solenoid valve was damaged, and they were making contact with each other. I cleaned and re-insulated them and reconnected them. Unfortunately, this didn't solve the problem either."

There are no error codes stored in the error memory.

Does anyone have any other ideas about what might be causing this?

Thank you in advance.

Autoscan?