Cold start problem with the 1Z engine not solved *cry*

Hi!

After I replaced the coupling gasket, glow plugs, bearings and seals in the ESP and hydraulic unit on my Passat TDI 1Z, manufactured in 1995 with 174,000 km, the cold start problem (10 seconds of cranking plus white smoke) is unfortunately still present .
After a few seconds, the engine runs like new: endless power (intake manifold cleaned, EGR valve broken), it consumes almost nothing, no soot, no valve clatter, very quiet... when starting warm, the engine starts immediately! There are also no more air bubbles coming out of the ESP. I don't understand this. I'm currently building Ulf's adapter, and then I'll take a closer look at the fuel quantity meter.
Mit der Kurbelwellenschraube habe ich mich ebenfalls beschäftigt: Es ist die 12.9 drin und der statische Förderbeginn steht exakt bei 0,7 mm Hub!!! Es ist natürlich die Frage wann diese Schraube gewechselt wurde und ob dabei schon der Kurbelwellenstumpf beschädigt war? Sollte hier aber das Problem liegen, dann müßten sich aber auch der statische Förderbeginn und die Steuerzeiten verstellen oder irre ich mich (dynamische Prüfung bald möglich mit VAG-COM)? AuFurthermore, it's unlikely that after a complete reset of the timing and a 10 km test drive, everything would be misadjusted to such an extent that this problem immediately arises!
It definitely has something to do with the temperature and the associated EDC (Electronic Diesel Control) system of the engine! Unfortunately, I'm not an ESP (Engine Stability Program) specialist. However, it could be that the fuel delivery is insufficient (fuel quantity control? temperature sensor? crankshaft position sensor?). Also, there seems to be an additional exhaust smell during the initial phase (first 5 minutes after a cold start).
I once tried using the No Heat Generator (NHG) and then starting [something], but I think the smoke cloud was even bigger that way.
What else could be a problem?

Thank you in advance.

Best regards, Christian.

Nozzles also replaced?

They are due based on mileage!

Bertil wrote:

Nozzles also replaced?? Bei der Kilometerleistung sind die fällig!!

Hi Bertil!
I've already considered that, but I know some people who have driven theirs for over 250,000 km without any problems. In my old glow plugs, there were no diesel residues! Also, the engine might sound a bit rougher, right? It's definitely an expensive undertaking with the risk that nothing will change!

Best regards, Christian .

haehnlein wrote:

Mit der Kurbelwellenschraube habe ich mich ebenfalls beschäftigt: Es ist die 12.9 drin und der statische Förderbeginn steht exakt bei 0,7 mm Hub!!! Es ist natürlich die Frage wann diese Schraube gewechselt wurde und ob dabei schon der Kurbelwellenstumpf beschädigt war? Sollte hier aber das Problem liegen, dann müßten sich aber auch der statische Förderbeginn und die Steuerzeiten verstellen oder irre ich mich (dynamische Prüfung bald möglich mit VAG-COM)?

Hi Christian,

As long as the injection adjustment in the pump and the NBF (No Backflow) are okay, a misadjusted engine control can also be detected via the injection start regulation - provided that you haven't corrected the pump setting afterwards.

Quote:

However, it's possible that the amount of fuel being supplied is insufficient (fuel flow meter? temperature sensor? oxygen sensor?). Also, there's an additional smell from the exhaust during the initial phase (first 5 minutes after a cold start).

If the problem is related to the coolant temperature sensor, you can diagnose it using a VAGCOM device.
Abgasmuff könnte u.U. auch von verschlissenen Düsen kommen . . .
If the pump's flow rate were insufficient for a cold start, that would be very unusual.
I would also suspect the injectors in that case, especially if the proportion of very fine, easily ignitable droplets in the spray has become too low.

Subject: Regarding the glow plugs, you only mention new candles. Have you ever measured whether they actually receive voltage during preheating (disconnecting the engine temperature sensor connector for safety)?
Sometimes, a fuse blows and throws a wrench into your plans .

Then there's the issue of valve stem wear, which allows compression to escape only in the top dead center (TDC) area, and whose effects can actually only be compensated for by increasing the cranking speed.
This can be checked with a standard compression test.

Hello Christian!

Even though it might sound a bit simple, have you tried disconnecting the coolant temperature sensor? I don't know how it works on your engine, but on my AFB engine, it's a dual-sensor that provides information to both the engine control unit and the temperature gauge.
My car starts very poorly, even with new glow plugs, and doesn't preheat at all. Compared to another AFB that does preheat, it's a world of difference. That's why I already replaced all the glow plugs on suspicion in February... for nothing .
I once checked the coolant temperature for preheating using VAG-COM, and it showed a difference of about 7°C compared to the outside temperature. In my opinion, this deviation is too large after being stationary for 12 hours.
As a test, I unplugged the connector so that the control unit thinks it's extremely cold . Then it heats up wonderfully. If you then start it after 4-5 seconds, the cold start works perfectly! Maybe it also has to do with the extremely large amount of fuel injected at that time!?
I got a new sensor today and I'm going to install it in the next few days. I hope this solves the problem.

Unfortunately, I still cannot increase the initial amount on my AFB because, for some reason, logging in with the usual code is not working. It's also not working on another AFB... it must be a different one there! Unfortunately, no one has been able to help me with this yet .

Regards,

DENNIS

Thank you for the helpful and informative answers!

I had also been considering the NBF. During the test drive when I bought the car, it experienced a momentary loss of power in 4th gear at 130 km/h. However, that might have been due to a faulty crankshaft seal on the ESP (which was leaking air)! So far, I haven't noticed anything myself (but I also don't drive aggressively). A friend of mine (with an Audi A4 1Z) replaced that part, and the jerking problems disappeared.

If the nozzles are defective, that means they drip after the engine is turned off, which allows air to enter the pressure lines, right? To avoid unnecessary expenses, I've come up with the following idea:
If Dennis is right, then the car should start without any problems after being exposed to a hot air blower for a longer period of time, or what? If it doesn't, then the injectors are probably damaged!

"However, I still can't quite imagine that the injectors are to blame. In principle, after every replacement of the fuel lines, diesel filter bleed valve, etc., this white smoke problem should occur during the first start-up. But I don't recall this happening in other cars, except perhaps a little hesitation when starting."

Verbessert mich bitte, wenn ich falsch liege!

Best regards, Christian.

haehnlein wrote:

... If the nozzles are defective, that means they drip after the engine is turned off, which allows air to enter the pressure lines, right? To avoid unnecessary expenses, I've come up with the following idea: If Dennis is right, then the car should start without any problems after being exposed to a hot air blower for a longer period of time, or what? If it doesn't, then the injectors are probably damaged! ...

Hi Christian,

"If the injectors are dripping, it doesn't necessarily mean air is entering the system. However, it means there will be a puddle of diesel in the cylinder. When the engine is warm, this isn't usually a problem because the amount of fuel injected during startup is already small. But with a cold engine, you have so much excess diesel (a pool of diesel and an extremely high starting quantity) in the combustion chamber that not all of it burns, and it comes out as white smoke."

Is it worth considering?

"Try searching in this forum; several other users have experience with refurbished injectors (including Rudi, DocSnydor, myself, and others)."

Bertil wrote:

If the injectors are dripping, air doesn't necessarily enter the system. However, you then have a puddle of diesel in the cylinder. When the engine is warm, this isn't a problem because the starting amount is already small. But with a cold engine, you have so much excess diesel (diesel puddle and extremely high starting amount) in the combustion chamber that not all of the diesel burns and it comes out as white smoke at the back.

Hm... I had removed the cylinder head, and besides a few glow plug fragments and some soot, there was nothing visible on the pistons! Or does diesel evaporate that quickly? (I don't think so.)

Recently, I replaced the injectors on my father's Audi 80 TDI (260,000 km). There was a slight reduction in soot (it doesn't smell as bad anymore), a bit more power, and slightly lower fuel consumption, but no significant change. We only replaced them out of fear of piston damage... but it started just as well before, even with the glow plugs disconnected!!!!!!!

This morning, mine even shut down twice. But after the warm-up phase, I easily reached 180 km/h without any jolting or hesitation.

Rainer once wrote that you can also check the injectors using VAG-COM (to see the fuel distribution to the cylinders). Hopefully, with a bit of luck, Ulf's adapter will be finished tomorrow, and then new possibilities might open up.

Or does one have to start questioning German engineering? It can't be that one engine lasts 300,000 km with all its original parts, while another starts having problems at just 174,000 km (unless my previous owners mistook the Passat for a Ferrari). Are the manufacturing tolerances so high??? Probably you have to buy a Toyota or install those good old diesel engines.

Best regards, Christian.

haehnlein wrote:

... Or does diesel evaporate that quickly (I don't think so) .

Diesel evaporates extremely slowly (almost not at all).

Quote:

... This morning, mine even shut down twice. But after the warm-up phase, I easily reached 180 km/h without any jolting or hesitation.

I can't say anything... it doesn't sound like a jet engine.

Quote:

... Rainer once wrote that you can also check the injectors using VAG-COM (to see the fuel distribution to the cylinders). Hopefully, with a bit of luck, Ulf's adapter will be finished tomorrow, and then new possibilities might open up.

You can only test for performance differences between individual cylinders. This allows you to indirectly infer information about the injectors, but this is very unreliable. It's better to have the injectors tested: assess their opening pressure and spray pattern (have it done professionally).

Quote:

... Or does one have to start questioning German engineering? It can't be that one engine lasts 300,000 km with all its original parts, while another starts having problems at just 174,000 km (unless my previous owners mistook the Passat for a Ferrari). Are the manufacturing tolerances so high??? Probably you have to buy a Toyota or install those good old diesel engines.

Fuel injectors are wear-and-tear parts!!!!!! (please refer to older threads for more information).
Or can a gasoline engine also last 300,000 kilometers with a single set of spark plugs?
It doesn't matter which car brand we're talking about. The injectors were already a wear item in the TD engines, and they are also a wear item in Toyota engines. They all work on the same principle, but in TDI (+CR) engines, the higher pressures cause greater abrasive wear on the injector needles compared to WK or VK engines. This wear is heavily dependent on the quality of the fuel used (foreign particles in the diesel).The springs in the nozzle block will inevitably weaken over time, which causes a change in the opening pressure. It is impossible for even a Toyota engineer to prevent this from happening.
If the rice cooker can defy the laws of physics, then buy one and be happy with it.

Bertil wrote:

Fuel injectors are wear parts!!!!!!! (please read the old threads about this). Or can a gasoline engine also last 300,000 kilometers with a single set of spark plugs? It doesn't matter which car brand we're talking about. The injectors were already a wear item in the TD engines, and they are also a wear item in Toyota engines. They all work on the same principle, but in TDI (+CR) engines, the higher pressures cause greater abrasive wear on the injector needles compared to WK or VK engines. This wear is heavily dependent on the quality of the fuel used (foreign particles in the diesel).The springs in the nozzle holder continue to weaken, causing a change in the opening pressure. It is impossible for even a Toyota engineer to prevent a spring from weakening over time. Wenn der Reiskocher die Physikalischen Gesetze ausser Kraft setzten kann, dann kauf dir einen und werd glücklich damit.

Hi Bertil!

I certainly don't want to question the physical limits!! But I'm still surprised that my father's car manages 260,000 km without any problems (and others do too), despite only having had the fuel filter changed twice and using fuel from "independent" stations, while my meticulously maintained vehicle is completely unreliable!

Das klingt für mich eher nach verschiedenen physikalischen Grenzen aufgrund starker Qualitätsunterschiede!!! Wenn ich beim ICE von Radreifenbrüchen und Kupplungsrissen höre, dann war natürlich die "physikalische Grenze" schuld, was aber heißt, dass die Konstruktion eine Katastrophe war (ist)!!!!!!!! Deshalb ist doch die physikalische Grenze von der Konstruktion abhängig und hier gibts bestimmt Spielraum. UAnd the natural gas engine in the 1Z is really not a masterpiece of engineering at all!

I just want to make sure that before I go out into the snow again and spend another 380 euros to check the injectors, there isn't something else causing the problem!

But thank you for the effort you are putting in!


Best regards, Christian.

haehnlein wrote:

Ich möchte doch nur bevor ich nochmal im Schnee stehe und für 380 Euro Düsen reinschraube überprüfen, ob nicht etwas anderes noch die Ursache sein kann!!!

Hi Christian,

Other possible causes were also mentioned.
Then, why don't you check that first? Maybe it's not (mainly) due to the nozzles .

Hi Ulf!

So, waiting for the VAG-COM...

I'll still order an NBF though. I know a mechanic who experienced engine damage due to a faulty NHG and has been replacing it preventatively every 90,000 km ever since. Hopefully, that will improve things.

Best regards, Christian.

haehnlein wrote:

Also warten auf VAG-COM.........

Hi Christian,

Not necessarily: Things like spark plug wear and blown fuses will not be displayed by VAGCOM .

Quote:

I know a mechanic who experienced engine damage due to a defective NHG

.

Wow, is that secure? What exactly was affected by the broken NHG (National Housing Guarantee)? Which MKB (Mortgage Credit Bond) are we talking about?

Hi Ulf!

It seems that the fuel flow was too high due to the incorrect distribution of the electronic distributor coil (EDC) in the third cylinder (in a single-cylinder engine), which caused the piston to seize. That's at least my understanding of what happened.

I called Bosch and VW again:

VW: Nozzles are dripping.

Bosch: At 174,000 km, it's unlikely to be a problem with the fuel pump itself; more likely, there's an issue with the mechanics inside the pump, specifically the injector control valve.

aach why am I just so impatient: because he stood on the street for 6 weeks without a head, and winter is just around the corner .

Best regards, Christian.

haehnlein wrote:

It seems that the fuel flow was too high due to the incorrect distribution of the EDC in the 3rd cylinder (in the 1Z engine), which caused the piston to melt (at least, that's how I understood it).

Hi Christian,

"In my opinion, this is very strong stuff... the EDC system only distributes fuel during idle, which is called an idle stabilization system."
However, the amount of idle fuel is probably not sufficient to melt pistons, as far as I know.
(I'm not accusing you of anything; it's likely someone gave you incorrect information, or there's been a misunderstanding.)

A piston can without any modifications likely only be melted down due to an extremely poor fuel injection pattern under high engine load.
This can happen in any cylinder, regardless of whether or not a Nozzle Back Flush (NBF) is still attached.

So, for me, the history doesn't provide a reason to replace the expensive NBF as a precaution – it should be either all of them or none.
Or am I wrong? Nozzle specialists are available before .

Hello,

I just read the story, and I don't understand why it keeps focusing on the injectors. If the engine runs properly except during or shortly after a cold start, I would first check everything related to the glow plug system (glow plugs!). Blue smoke coming from the exhaust doesn't necessarily indicate faulty injectors.
And a lack of compression due to wear on the valve seats is also unlikely to be the cause of reduced performance over time.


Best regards, Albrecht.