Glow Plugs Fault? Engine Won't Start

Hello!

I have a G3 AHU, AXG injectors, a chip, an LD increase, 223700 km on the odometer, and I'm experiencing a 'slight' starting problem.

I have to let it idle for about 20-30 seconds before it starts sputtering. Once it's running, it works perfectly fine, and it still reaches its top speed of 215 km/h. It also starts immediately at the gate (meaning when the engine is still warm).

I suspect the glow plugs might be the problem.

When bubbling, white smoke initially comes out from the back, which then gradually becomes darker. After about 20 seconds, I can't see my house wall anymore because of so much smoke.

Before I rush off to VW and buy glow plugs for €100, I wanted to know if any of you have any ideas about alternative potential causes for the problem.

fuel injection start or pump activation is misadjusted, or the crankshaft sprocket has become loose.

Just search for it.

Hello Henrik!
As far as I know, AHU = 1Z because the engine numbers for the 1Z have been discontinued (if anyone knows better, please correct me...). The problem you described sounds like the very well-known issue with the crankshaft screw on the 1Z... try searching for '1Z' and 'crankshaft' in the search function; you'll be overwhelmed with search results. I also sold my Passat about 3 weeks ago with a new crankshaft gear, secured with a lot of red Loctite, to Serbia, for a good price... . It wouldn't have been a problem if it hadn't been the second one within 20,000 km, and the crankshaft had already lost a lot of material .
Certainly, let's troubleshoot this: use a VAG-Com or a VW diagnostic tool and check the injection start and injection advance control at idle. If you get any fantastic values that are completely out of range , it's 100% the crankshaft pulley or a loose, possibly cracked, timing belt; the latter would be extremely rare. The fact that your engine is still reaching its maximum power is understandable. The fuel injection pump compensates for this, but not during cold starts, where everything needs to be correct. And with a loose pulley, the injection timing shifts towards being too late.

Best regards,

Dominique.

Oh man, those are some scary stories!

I'll probably go to VW (if I can still get there) and check the values.

If these values deviate significantly, can I still exchange something, or should I just discard the entire engine?

Nothing is thrown away.
Check it out as described; if the KW wheel is damaged, then you can fix the problem. Read through the forum; this has been discussed many times before.

Good luck!

Sooooo!

'I took out the glow plugs today... they were completely black and no longer responding at all. All four of them. Completely dead. No spark when I held the battery cable to them, let alone any sign of them glowing. The tips were cold to the touch.'

Okay, I just put in new spark plugs... the engine is running perfectly again!

Henrik wrote:

So, I put in new spark plugs......the engine is running perfectly again!

Hmm... how cold was it when your engine wouldn't start?

Hello Hendrik!

I can't imagine that it was just the spark plugs.
My TDI started even at -15°C with 4 faulty glow plugs!

I'm also leaning towards a loose wheel nut.

Regards,
Alex.

Hello!

The temperature was between 15°C and 5°C, always the same. I know the candles only light up when the temperature drops below 7°C.
However, it must be related to that.

Now, he's doing something different.

I start it up, and for 1 second, the engine runs at approximately 500 RPM, then it revs up to its normal idle speed after 1-2 seconds.
I suspect the first ones are starting now, and then the others will follow.

I'll check the cable that supplies power to the burners tomorrow, even though I can't imagine anything being broken inside.

The mechanic listened to the engine and said it could only be one thing: it's running smoothly, there's no knocking, no play, and it's revving normally.

Tomorrow, we will also be checking the alignment of each wheel on the belt.

At least it starts immediately after the glow plug replacement, and only produces white smoke for the first 1-2 seconds.

@donalexo:
It's possible that your candles have a preheating mechanism, meaning they are designed to be pre-warmed. Perhaps that's why they started in the winter. Also, my candles were practically dead; you could touch them without getting burned. Maybe yours at least had a little bit of preheating.



Oh yes, the oil temperature is rising faster since the spark plug replacement?! Usually, it took 7 kilometers for the display to reach 70°C, but now it only takes 4 kilometers???

Hi,

It can't just be the glow plugs. As Alex already mentioned, a healthy TDI engine will start even in sub-zero temperatures without preheating (my personal record: -10 degrees Celsius, and I accidentally revved it too high, but the ASV started almost immediately and ran, albeit a bit rough at first).

I would definitely keep looking in your place; there must be something else.

Best regards,

Jan.

Hmm, so I guess our old 1Z had the exact same behavior when it was cold and hadn't been preheated. It wouldn't run on all the burners, but they would eventually come on. How old is the battery?

Best regards, WarLord.

Okay, I have some news.

After spending 8 hours with a friend searching for the problem, I discovered that the coolant temperature sensor was simply defective. Unfortunately, we only tried that as a last resort... ...we even recreated the relay and plugged it in using homemade contacts......man!

'One problem solved... but two new ones found: It's leaking oil from either the exhaust manifold or the head gasket. I cleaned everything with brake cleaner, and tomorrow I'll try to figure out where the leak is coming from.'
Second problem: After starting and idling, the engine drops in RPM slightly, perhaps by 50 RPM, and makes a strange noise. After running for about 5 minutes, the RPM increases again, and everything sounds normal. However, if I then turn on electrical consumers (e.g., electric windows), the RPM drops again by about 50 RPM...

I'll see.

The decrease in speed followed by an increase could very well be related to afterglow.

Attach a test lamp to a glow plug and observe the RPM.

I bet that when the light goes out, the speed increases .

I don't know if the limiter is allowed to force the engine to shut down like that.
Normally, it should detect the load on the DF clamp using the Lima system and regulate accordingly.

Do you have the common 1117 engine fault?

Quote:

Error code: 1117. Load signal for generator terminal DF: implausible signal. Possible causes: Generator failure. Voltage regulator faulty. Power outage.

Perhaps this will be helpful to you.

m;

Do you have the common 1117 engine fault?

Error code: 1117.
Load signal for generator terminal DF: implausible signal.

Possible causes:
Generator failure.
Voltage regulator faulty.
Power outage.


Perhaps this will be helpful to you.

m;


Thank you for the information!

The error memory is clear; there was only an implausible signal from some control unit, which was control unit 25 (or 24?). I've forgotten what kind of unit it was, but it certainly didn't seem important .

Okay, I'm going to try using the inspection lamp today!

I'm still having the problem.

First of all: All the timing belt alignment marks match perfectly.

Sure, please provide the text you would like me to translate from German to English.
Glow plugs are new. The temperature sensor for the preheating system is new. The relay is functioning as it should according to the wiring diagram.

Alles durchgemessen. Es ist so, das er zuwenig (zu kurz) vorglüht. Fuses are OK.

Okay, here's the translation:

'Now for the surprising part: if I disconnect the plug from the temperature sensor, the glow plugs activate for 20 seconds, there's 12V at the glow plugs, and the engine starts immediately. After that, I can plug the connector back in.'

Unfortunately, I don't have a proper wiring diagram, but in my book (which unfortunately only covers TDI engines up to around 55,000 km), there's some information about the glow plug control unit.

It can only be a problem with the sensor itself (it seems to always output a value indicating that the engine is warm and doesn't need to be preheated; if you unplug the temperature sensor, it thinks the engine is ice cold and will preheat).

Now, here's my question, which has been occupying my mind for the past 5 hours:

Where is the glow plug control unit?

Don't say that's the engine control unit next to the pollen filter... that costs 900€.

@Henrik
So, at temperatures around 10°C, it doesn't need to glow. Therefore, the very brief glowing you described is perfectly normal.

If the necessary compression pressure cannot be achieved due to another defect (e.g., due to high mileage > 220,000 km), then a significant pre-glow period will certainly help with a perfect start. You achieved this by disconnecting the temperature sensor. However, the defect is definitely located elsewhere. If the valve timing and injection system are okay, then the most likely causes are worn cylinder bore surfaces (especially the upper dead center of the piston) and, as a result, insufficient compression.
Correct me if I'm wrong (but don't stone me right away ).
Even with poor compression, the TDI engine still achieves almost its rated power.
Have the compression checked, and you'll likely find the problem.