Unable to establish connection (diagnostic line)

I have a 1994 Passat 1Z TDI that hasn't been starting for quite some time.
I went to a Volkswagen workshop to have the error codes read, but it was unsuccessful.
I was unable to establish a connection to my device using either the 1551 or the 5051 testers.
Has anyone ever experienced something like this before?

I've been searching for the source of the error for quite some time now!
checked:
Pre-glow system OK (spark plugs new, I-connector OK).
Timing belt adjustment: OK.
Starting speed: OK.
Fixed-hub ZR wheel.
Intercooler disconnected (possibly clogged).
KW sensor signal is OK.
Needle insertion sensor signal OK.
Solenoid valve for injection start (easy to operate, moves freely).
Quantity-setting mechanism (operates, moves).
Temperature sensor, new.
HDK is showing a correct voltage of 2.5 volts.
Fuel available.
I'm sorry, but I can't translate a text that consists only of question marks. Please provide the text you would like me to translate.

It started once at 2 degrees Celsius and smoked a bit, indicating incomplete diesel combustion, but it wasn't too bad. My suspicion is that it's the fuel injectors. The car has 259,000 km on it, but it hasn't had any other starting problems before.
My girlfriend made the last trip. According to her report, it was already emitting white smoke while running, and it lost and regained speed.
I'm thinking that when it starts producing white smoke (from the exhaust), the internal pressure of the pump will be correct.
(Does anyone perhaps know where I can get a pressure gauge with an adapter?)

I need a mechanical dial indicator to check the electric pump (no access to the measurement block). Does anyone have DIY instructions for building the extended arm for the dial indicator, or perhaps a cheap set available?

Does anyone have any idea how much injector components cost for a 1Z engine?
Does anyone know where I can get automotive data information for pins, to check wiring?
Does anyone have any idea why a diagnosis isn't possible?

Help, help...

I am grateful for any helpful information!

Best regards, Tread !!

White smoke can be caused by either a coolant leak -> head gasket, or by incorrect fuel injection -> N108 (fuel injection control valve) or -> engine control unit.

It seems that the STG (steuergerät) is not communicating properly. Try using a different STG.

At the beginning of the injection process, the timing and head gasket are misaligned, preventing the engine from starting.

m;

Have you ever measured the compression?

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

The spark initiator works when it is energized (possibly...). The head gasket is consuming too little water for my liking (minimal water loss).
The next steps I will take are a compression pressure test, and if necessary, a leak test. I hope there are compression pressure testers that can be inserted into the nozzle bore, because one glow plug is stuck and won't come out. If that's okay, where can I get a sewing machine at a reasonable price (i.e., at the normal price), and how much does one typically cost?
Is the compression primarily measured through the glow plug opening in a TDI engine?
Where can I find compression testers and pressure loss adapters for diesel engines (universal set)?
Does the TDI engine fail to start at an outside temperature of 8 degrees Celsius if the fuel injection timing control is no longer activated?
Questions upon questions;...

You're welcome!

It sounds more like a search function and a timing belt sprocket...

The timing belt pulley on the crankshaft is stuck and won't move. I've already tried the trick with the fuel cap, and I've also checked the 109 relay. ???

The 1z should have an HDK (Hall-effect sensor) for detecting the position of the switch machine (EP). I recently read in a forum that if you open the cover of the EP, Bosch would need to re-calibrate it. I haven't heard of that before! I'd like to take a look at the spring of the HDK, as it could also be responsible for starting problems. Please reply.

No, you can safely unscrew the lid. You only need to make adjustments if you completely remove the entire point machine.

The compression test is typically performed through the injector bore. Expanding the nozzles also gives you the opportunity to have them thoroughly inspected by a reputable mechanic or a qualified Bosch service center.

I checked, and it turns out that different types of injectors are used in the 1Z engine series. The price range is from €164 to €355, depending on which nozzle is installed.

I didn't see a repair kit at the dealership.

Happy Easter to everyone in this forum!
Regards,
Golfchriss