Another TDI acting up...

Hello,
I have a Passat TDI, manufactured in October 1994, and it's acting up (nothing new about that).
'I'm having this problem: the car sometimes starts poorly (whether it's cold or warm), and it keeps stalling while driving, with the preheating light staying on constantly... I also feel like the preheating light isn't working properly anymore.'
I couldn't retrieve any information from the error memory. I then replaced relay 109, replaced the diesel filter, and just for fun, I put in a different injector nozzle... so far, it hasn't done anything.
Can someone give me a tip?

Paserati.

Hello,

Have you already checked the clear fuel hose from the diesel filter to the injection pump for air bubbles before starting?
What happens inside the hose while the engine is running?

Please also read through http://www.dieselschrauber.de/vptdifehler.html, and consider whether you have forgotten anything.

Best regards, Rainer.

Hello Paserati,

What is your occupation code?

Hi,
MKB?? I think it's 1Z...

Fuel lines often have more air than diesel.
I'll start looking into it.
See you later.
Paserati

Hello,
I put your suggestions into action... (I bled the ESP and sealed the lines).
What can I say... the car is running better now... and it doesn't have starting problems anymore (but here comes the catch), but it still turns off.
As I mentioned before, it happens while driving (regardless of the speed).
Engine control unit, immobilizer, or fuel injection pump???

See you later.

Hello,

Have you read the error memory again?
Is the preheating indicator still illuminated continuously?

Hello Michael,
You won't believe this... but the error memory shows nothing!
I read it immediately after opening it... (thanks to my laptop and the appropriate software ).
Here's how it works with the preheating light:
As soon as the box runs out of power, a light comes on (continuously), and it can crank for a long time... However, if I remove the key after it stops running and wait about 10-20 seconds before restarting, everything is 'normal' again. The preheating light briefly illuminates, and it starts immediately without cranking... (and I don't know when the next 'failure' will occur; it's sporadic).Bye.
Paserati.

Hi Paserati,

I had the same problem as you. The car just shuts off. After that, the preheating light doesn't turn off. ->>>> Relay 109.

I know you've already exchanged it. But if you have the opportunity, try testing a different one. I've heard from several people that the new ones are also faulty. Do you have the smaller gray one or an older black one?

By the way, my error memory was also empty.

Best regards.
David.

Hello David,
Thank you for your tip!
The old 109 was black... I've now tried the third one... nothing helps... however, these were gray!

Something different:
'If my car stalls and I tap the dashboard on the left side of the A-pillar, the preheating light turns off and I can start it normally. If I tap it while the engine is running... well, you have three guesses as to what happens...' (it stalls).
...and that's where the control unit for anti-theft protection is located...
My question:
Can I simply remove the old part and install a new one, or does installing a new control unit require significant programming work?
(I was at VW today and wanted to buy a new control unit... they claimed that only VW itself ).

Bye.
Paserati.

(Passat TDI, 66 kW, 1Z engine, 149,000 km mileage)

Hello,

When installing a new water pump (WFS), it must be adapted to the engine control unit (ECU).
A code is required for this, which can only be generated by VAG. This code is also only valid for one day.
Installing and configuring the WFS is actually not a problem.

Hello Michael,
Do you mean by 'new' WFS a device that is currently available in the shelves at a VAG dealer and compatible with all transponder-based WFS systems since their introduction (possibly after coding), or a device that is identical in construction to the old one?
I adjusted the settings on my '96 model (after replacing the engine control unit) using the 1552 tool.
- 25 (WFS)
- 10 (adjustment)
- 00 (Channel 0)
- 'Delete learning values' acknowledged.
Ignition off - on again -> works.
Without VAG code.
How is the validity period of the code actually determined in the new immobilizer systems? Is it based on a real-time clock (RTC) or a timer that expires after approximately 24 hours?

Best regards, Rudi.

Hello Rudi,

You're right. The code will be available a bit later. It's the same situation with the '94 Passat.

@Paservati,

Have you already checked the cables and connectors for any breaks or loose connections?

Hello there,
I examined the 'cable mess,' and it seems everything is in good working order...
I think there's a 99% chance that it's due to the WFS... I took out the control unit and disassembled it (not completely )...
'There wasn't anything particularly special to see... After the installation, it ran for 2 days without any issues... I was almost happy... (but it was too early).'
Okay, I'll get that part replaced.
See you then.
Paserati.

Do you really think it's due to the WFS or the DWA?

You can test it like this: Put the key in the ignition, lower the driver's side window, and lock the car from the outside. Then wait until the LED starts flashing rapidly (indicating that the alarm system is activated), and then try to start the engine with the key.

Okay, with my car, it immediately starts honking and flashing its lights. And no warning lights come on or anything like that!

I don't know how much you care about your dashboard, but maybe the problem is actually located a bit lower down (in the central electronics).

Hi David,
'It's not like I'm going to take all my anger out on the dashboard...'
I'm just tapping very lightly (subjectively), well, more or less like knocking on a door!
I tried it... I inserted it and locked it from the outside... just like you said, there was a honk and flashing lights.
Regarding the central electronics: at first, I also thought something might have blown or shorted out. So, I removed the panels around the fuse box and steering lock and did quite a bit of measuring... Well, back then I installed a new fuse box... but it wasn't the problem.

To make sure it's the WFS (Water Flow Sensor), I removed the light switch (this gives me direct access to the control unit). Now, if I let the engine run and gently tap it with a screwdriver... the engine shuts off! Don't ask me why; that's just how it is.
The only thing that helps is to try it out!

Hi,

I once had a Passat, and the problem was with the anti-theft system. There's a relay in there that cuts off the power supply to all components. Do you have an anti-theft system? If so, try removing the control unit and soldering the contacts of the relay together. The control unit is also located on the left side.