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Hello everyone, dear experts.

Initial situation

For quite some time, I had planned to replace the timing chain. I have now done that, but a problem occurred that I cannot resolve.

The timing chain was replaced, all timing marks were set correctly and checked multiple times. Everything was aligned properly. After that, I fully reassembled the engine: all sensors connected, everything mounted correctly.

Nevertheless, the engine no longer starts.

First diagnosis

After the unsuccessful start attempt, I connected ISTA to check for faults. My first thought was an air-bleeding issue or something similar.

Yes, bleeding is generally required, but according to ISTA, 0 diesel pressure is reaching the fuel rail.

Step-by-step troubleshooting

I then continued checking systematically:

Checked the high-pressure fuel pump
Checked the pressure control valve / IMV
Inspected everything related to the fuel system

After that, I also checked all fuses, because an incident had occurred earlier:

During reassembly, a battery charger was connected. I wanted to tighten an engine mount nut using a long wrench, and the wrench accidentally touched something and caused a short circuit.

The vehicle was switched off at the time, so I initially assumed it could not cause any issues. Nevertheless, to be safe, I checked all fuses — no faults found.

Low-pressure (pre-supply) fuel pump check

Next, I checked whether diesel was being delivered at all.

Normally, during bleeding via ISTA or when switching on the ignition, you can hear the low-pressure fuel pump at the rear of the vehicle.

However, it was completely silent.

So I supplied the low-pressure pump directly with 12 volts — and it ran perfectly.

After that, I checked the hose at the outlet of the fuel filter:
➡️ Absolutely no fuel came out, not even a small flow.

This made it clear:
The low-pressure pump is mechanically fine, but it is not receiving a control signal to activate.

EKPM check

My next suspicion was the EKPM (fuel pump control module). I thought it might have been damaged by the short circuit.

Ordered a new EKPM
Installed it

➡️ No change — still no fuel delivery.

Sensors / Crankshaft position sensor

The crankshaft position sensor (CKP) is connected. I even removed and checked it again.

Installed correctly
Properly secured with the bolt
Installation depth appears correct

So far, everything I can think of has been checked.

Current status & open questions

The only remaining assumption from others is the following:

The DDE is not sending a signal to the EKPM to activate the low-pressure fuel pump.

My questions are:

What could be blocking the DDE?
Why is the signal not being released?
What might I have overlooked?
Has anyone experienced a similar situation after a timing chain replacement?

I have reached a point where everything seems to be checked, but the issue remains unresolved.

Thank you in advance for any helpful ideas.