Passat TDI: Cold Start Problems & Solutions

Hello everyone,

I'm having the following problem with my Passat 1.9 TDI, manufactured in 1994, engine code 1Z: The engine only starts after a long cranking period!

It started like this: the engine would start poorly, even when it was warm. I then replaced the diesel filter, but that didn't improve anything!
Since the timing belt was due for replacement anyway, I had it changed. However, there was no improvement, so I used VAG-COM to read the error codes.

'17978 - Engine Control Module Blocked by Immobilizer 35-10 - - - Intermittent'

That's probably the explanation for the startup problems that have occurred before.

'But now I'm having these problems every morning: the engine doesn't want to start (with the warm start problems, which I suspect are due to the immobilizer, the starter motor just spins and the engine doesn't even try to turn over). It only starts with a lot of gas and a long cranking period.'
Once the engine starts, it restarts immediately.

After further searching, I then replaced the four faulty glow plugs, but there was no improvement (apparently, the engine doesn't need them if everything is working correctly).

Then I reinstalled the old diesel filter, but that didn't help either!

What I also discovered using VAG-COM was that the timing values were slightly below the lower limit.

I'm desperate!!!!!!

Regards,

DICC

Hi,

dicc wrote:

What I also found out with VAG-COM was that the timing values were slightly below the lower limit!

Try using the search function. Enter "crankshaft bolt 1Z" and check the box that says "search for all words." Then you'll find everything important. Instead of "1Z," you can also try "AAZ" – the engine has the same problem as the early 1Z models.

/viewtopic.php?t=3313&highlight=crankshaft+screw+1z
http://home.arcor.de/sgrafen/salatoel/kw_schraube/kw_schraube.html

Hi, the screw and washer were also replaced when the timing belt was changed. I was shown the old washer, and everything looks okay.

DICC

dicc wrote:

Hi, the screw and the washer were also replaced when changing the timing belt. I was shown the old washer, and everything was okay. DICC

Okay, then check your injection timing in the basic setting mode... if you're getting different values every day, that's perfectly normal.

Best regards, Rainer.

'Injection start in the default setting mode' - where can I find this information exactly, and what should the normal value be? What does 'everything is clear' mean in this context, and what is a 'toothed wheel'?

Regards,

DICC

Hello,
Have you ever checked the glow plug relay using the VAG-COM diagnostic tool? In my case, the problem was caused by a faulty relay. After replacing it, the 'organ-like' noise disappeared.
Bye.
Max.

Engine warm.

VAG COM
Engine.
Block 00.
Default setting.
Translate values 02 and 09 according to the usual conventions/graphics.

m;

Hello everyone,

'The problem is fixed. I didn't want to mess around in the cold anymore, so I finally took the car to BOSCH. The cause was air in the fuel system! They replaced a section of damaged hose and installed a new (different) diesel filter (it seems this problem occurs more often with the old ones), and now it's running again!'
The new filter no longer has this 'check valve'; it's simply bypassed with a connector so that the diesel fuel flows directly back into the tank! (What is the actual function of this valve anyway?)

Regards,

DICC

P.S. The filter has the Bosch part number 450906172 and costs €17.34, or the MANN WK842/3 is available from €8.95 online!

This large bump on the filter serves as a fuel pre-warmer.

It contains a bimetallic element that redirects cold diesel fuel back to the filter.
It only opens the bimetallic strip and allows the return flow back into the tank when a certain temperature is exceeded.

When the engine is cold, the diesel engine initially runs for a few short cycles before the ESP system warms it up more quickly -> this leads to better fuel atomization.

However, if there is a continuous short circuit, air may accumulate in the ESP (Electrostatic Precipitator), which is why the short circuit may clear after a certain amount of driving (i.e., heat).

While it's unfortunate that the part had to be removed, perhaps it was necessary to replace a potentially leaky connection.

That's why you now have much cheaper filters!

m;

[Translating...]@ max: wo genau finde ich die stellglieddiagnose für das Vorglührelais??

mit VAG-COM

ans MotorSTG verbinden

- 03 Outputtests

Dann macht er verschieden Sachen durch.

Nicht erschrecken N109 ist der Absteller, da geht der Motor aus !!!

Danach kommt irgendwann das Vorgluehrelais

m;

So dreht der Diesel bei kaltem Motor erst ein paar Kurzschluss-Runden und wird in der ESP schneller warm -> bessere Zerstaeubung.


eigentlich ist das ja zur filterheizung gedacht, um ausflockung im winter zu vermeiden

@dicc

danke für die rückmeldung !

CU Gremlin

dieselmartin schreibt:

'mit VAG-COM

ans MotorSTG verbinden

- 03 Outputtests

Dann macht er verschieden Sachen durch.

Nicht erschrecken N109 ist der Absteller, da geht der Motor aus !!!

Danach kommt irgendwann das Vorgluehrelais' .

So ist´s. Am besten den Motor erst gar nicht starten, nur Zündung ein. Im Menue wird dir dann u.a. der Test des Vorglührelais und danach der Test des Relais für die kleine und die große Kühlwasserheizung angezeigt. Bei den letzen beiden kannts du dann auch das 'kochen' des Kühlwassers im Motorraum vernehmen.

Tschüss
Max