Cold Start Problems: Engine Won't Start Below 10°C

Hello everyone,

MKB: ARL
Error memory: empty.

nachdem das Fzg. nach dem Kolben-Riss-Problem: https://community.dieselschrauber.org/en/viewtopic.php?t=19948 wieder läuft, zeigt sich o.a. Problem.

The engine starts roughly in cold temperatures, briefly smokes blue/gray, and idles erratically. Slightly increasing the engine speed (to approximately 1200 RPM) causes the speed to gradually increase (by about 100 RPM) and then decrease. This seems to happen each time the engine completes a combustion cycle.

When the engine is warm, it runs perfectly fine.

Nach allem was ich gelesen habe, ist eine Leerlaufruheregelung mit nicht springenden Werten im Bereich von -1 bis noch passabel (vgl. Logs).

Could someone please comment on the MWB documents 13, 18, and 23?

What else would need to be logged?

Steffen W gave me some information on how to test the glow plugs (thanks again). However, I think I read that the glow plugs only start to function above 5°C, but the poor starting behavior still occurs slightly above that temperature. I don't have the opportunity to test it right now, but I will do so later.

Given that there might still be some issues with the nozzle and PDE installation and re-installation performed by the workshop, my question is whether the MWB (Motordiagnosegerät - engine diagnostic tool) readings 13, 18, and 23 indicate any abnormalities.


Thank you in advance.

Best regards,

Okay, please provide the German text you would like me to translate.

Hello Bo,
Okay, first of all: All values are within the tolerance limits.
Well, the issue is that it's taking fuel away from the second cylinder and then distributing it to the others. When it's warm, it's not as noticeable.
It also immediately goes into the negative range in the MWB 23 if you press the accelerator. While everything is still well within the acceptable limits, we are still looking for the optimal settings.

When the engine is idling, the time it takes for the engine to reach 90 degrees Celsius is always compared. A cylinder that is more worn or has less compression will take longer. In that case, the fuel injection amount is increased to compensate. This amount is taken from the other cylinders so that the overall result is close to zero. Or vice versa. And you recently had a major overhaul done on the engine.

However, it's often due to the PDE (pump-injector-nozzle) or the fuel supply. You can only test the spray pattern, which is what you're interested in, by removing the PDE and sending it to Bosch, for example. If the spray pattern is poor, you'll also experience problems with the engine when it's warm and while driving.



"I logged that on my Passat yesterday, but it's not doing anything like that. And an AJM is not the same as an ARL. If I get a chance in the next few days to let my wife drive her Sharan with the ASZ engine, I'll see what that one does. Those engines are definitely more similar."

Below 5 degrees Celsius, it won't glow. That's correct. Therefore, disconnect the temperature sensor connector and use a diode tester or similar device to check the glow plug circuit. On the left side of the engine (when viewed from the front), there's a water flange with three glow plugs. The connector is located underneath it. It's a typical VW connector with 4 pins. Mine is olive green.

Maybe it's something simple like the battery? Or perhaps the starter motor is turning too slowly? Or a check valve in the fuel line that allows fuel to drain out if it sits for too long. But if that were the case, it would also happen on warm days. I'm not sure if the ARL engine has such a valve and where it would be located.


"Interestingly, our Sharan also did something similar, and that was even in the summer. It happened during the warranty period. We took it to VW, and they replaced the tandem pump, the fuel distributor, and the fuel pressure regulator. It hasn't happened since."

Just have the pump pressure checked. It's only about half an hour of work. It probably won't be very expensive, but then you'll know for sure.

Diesel filters (and maybe even toads?) should be fine with you.

What actually happens if you pre-glow the engine multiple times in the morning? Does it get better then?

Steffen W wrote:

However, it's often due to the PDE (pump-injector-nozzle) or the fuel supply. You can only test the spray pattern, which I understand is your main concern, by removing the PDE and sending it to Bosch, for example. If the spray pattern is poor, you would also experience problems with the engine running warm and while driving.

Ok, das beruhigt mich. It runs perfectly when it's warm.

Steffen W wrote:

Below 5 degrees Celsius, it won't glow. That's correct. Therefore, disconnect the temperature sensor connector and use a diode tester or similar device to check the glow plug circuit. On the left side of the engine (when viewed from the front), there's a water flange with three glow plugs. The connector is located underneath it. It's a typical VW connector with 4 pins. Mine is olive green.

You have difficulty accessing the glow plug connector block in the ARL engine due to the pressure pipes. The connectors, as the name suggests, are only plugged in, right? Although I could only reach the connector for cylinder 1, I couldn't pull it off, even with force. Since I currently have a fever , I didn't feel like disassembling the pressure pipe etc. in -5°C. I need to go back inside where it's warm.

Steffen W wrote:

Maybe it's something simple like the battery? Or perhaps the starter motor is turning too slowly? Or a check valve in the fuel line that allows fuel to drain out when the car sits for a long time. But if that were the case, it would also happen on warm days. I'm not sure if the ARL engine has such a valve and where it would be located.

The battery spins easily and delivers over 12V.

Steffen W wrote:

What actually happens if you pre-glow multiple times in the morning?

Does it then get better?

Maybe minimal.


I know, I should actually be providing test results now, but that's a bit difficult from my current state. So, for now, just some dry theory.

Yesterday, I took some more measurements. Specifically, I recorded data immediately after a cold start at -3°C, during the warm-up phase, and when the engine was fully warm.

I have calculated the average values for MWB 13.

The following values were obtained (cylinders 1, 2, 3, 4):

Cold start average........... -0.34... -2.27... 2.99... -0.60
Average warm-up phase: -0.01... -0.37... 0.04... 0.30.
Average (warm): .............. 0.00... -0.75 ...-0.09...0.82

Initially, after a cold start, cylinders 2 and 3 are misfiring more severely than in the logs previously posted. This might be because it was significantly colder.

Cylinder 3 initially receives a significantly larger amount, while cylinder 2 has a corresponding amount deducted. As the engine warms up, this difference becomes less pronounced. It's noticeable that it exhibits the smallest amount of variation during the warm-up phase.

From what I've read, the afterglow phase has a significant impact on the idle behavior as well.

My theory: The pre-glow/post-glow function is not working in cylinder 3. Consequently, the engine initially starts with only 3 cylinders firing. The poor combustion in cylinder 3 is being compensated for by adding more fuel, which initially only works to a limited extent due to the malfunctioning glow plug. [Speculation] It's possible that the excess fuel, which is not burning properly, is even cooling the combustion chamber, which in turn contributes to poorer ignition. [Speculation off]

The vehicle is an ARL model from March 2003, which means it shouldn't have an additional glow plug control unit installed.

Am I correct in my assessments? How long does an ARL (argon-filled lamp) glow after being switched off?


Best regards,

Okay, please provide the German text you would like me to translate.

Quote:

You have difficulty accessing the glow plug connector strip in the engine compartment due to the pressure pipes. The connectors, as the name suggests, are only plugged in, right? Although I could only reach the connector for cylinder 1, I couldn't pull it off, even with force. Since I currently have a fever , I didn't feel like disassembling the pressure pipes etc. in -5°C. I need to go back inside where it's warm.

I can only post reviews based on my own experiences with cars.
For the Passat AJM, they are individual angled connectors, similar to miniature candle connectors. And for the Sharan ASZ, it's a continuous strip with 4 connections. The entire strip is pulled down.
For the Passat, I use a long, flat-nose pliers. It's perfect for the job. Especially since the one on the 4th Passat is located halfway behind the distributor. For the Sharan, it's accessible without needing any special tools.

Cylinder 3 is getting way too much. When you're feeling better, you absolutely need to check your theory. Hopefully, it's just a spark plug. We really shouldn't even start talking about the PD (likely referring to a specific component or system), because that will cost a fortune. It only makes sense if it's a complex issue.
It's unlikely that the problem is related to compression, as that would affect all stages.

I'll check sometime to see what correction values my diagnostic tool has. Especially right after a cold start. I have the Sharan here today because it had a flat tire, but the interface is in the glove compartment of my wife's Passat. She has the Passat. I took the opportunity to replace the auxiliary battery under the seat. Now, on top of my cold, I've also got back pain. Something seems to be out of place.

Do you have a preheater, or even just that thing with the three glow plugs?

Here's some more information about afterglow: /viewtopic.php?t=4590

Steffen W wrote:

Cylinder 3 is getting far too much. When you are healthy again, you absolutely must check your theory. Hopefully, it's just the glow plug. We don't even want to start talking about the PD (presumably referring to a specific component or system), because that will cost a fortune.

Isn't it unlikely that a PDE would fail to work when cold, but function perfectly well when warm?

Steffen W wrote:

Do you actually have a pre-heater, or even just that thing with the 3 glow plugs?

Good question, how do I find that out? I guess I'll have to do some reading first...

Steffen W wrote:

Here's some more information about afterglow: /viewtopic.php?t=4590

"Thanks, I had already seen that. I also read that there are significant differences from vehicle to vehicle."

What I've noticed now is that the glow plugs are actually supposed to be activated for more than 5°C, but this isn't displayed on the instrument cluster, right? Then my theory might still be correct, if the cold start behavior is still not optimal even slightly above 5°C.

As always, thank you very much.

Best regards,

Okay, please provide the German text you would like me to translate.

Hi Bo,
The auxiliary heater is quite noticeable during the warm-up phase. It sounds like a stationary heater, making a loud hissing noise. Since you asked about it, you probably don't have one..

"When that starts up, it also affects the PD measurement blocks because it draws fuel. But only when idling. That's how it is with ours, anyway. You can also hear it rumbling."

Theoretically, it's possible that the PDE isn't sealing properly against the head. And if it gets warm and expands, then that could be the issue. However, in that case, it would be making noise throughout the entire warm-up phase. VW probably already installed new gasket sets. It's their policy that these rings must be replaced whenever the injectors are removed. That's why I don't think that's the problem.
Even internally clogged PDEs can be identified by looking at the main water balance (MWB) data, which will show very high values.

Try it with the glow plug. You can also use an H1 bulb. Connect one contact to the positive terminal of the battery and the other to the top of the glow plug. The light bulb should turn on.

Here, take a look:/viewtopic.php?t=20163

Look at Bo:/viewtopic.php?t=20171

This is a Log 13-18-23 from the ASZ. It behaves exactly like yours. When I give it gas, the BIP (boost pressure) goes negative. This Sharan has a new Difi (throttle body), a new knock sensor, a new tandem pump, and a new cylinder head with 4 new injectors. All are OE (Original Equipment) parts.

My AJM doesn't do that. But that's a completely different engine.

In other words: Don't worry about it, it has to be this way. Happy New Year.

Steffen.

Hello,
Where can I find out more about the MWB 18 and 23? I can't really make sense of the numbers/values contained within them. Today, after reading these threads, I also logged the cold AVB, drove a few meters, turned off the engine, loaded the car, and then continued on to the highway. /viewtopic.php?t=20182
What are the target values? In the MWB system, it seems there are only "0", "4", and "6" as possible values. What does that mean? What do negative values in MWB 23 indicate? What is the deviation from, and what is the reference point?
Is there perhaps a specialized article or other informative link about this? I would like to understand it better.
haithamina

Click on the label file for your engine control unit and then go to the corresponding measurement block. You will find comments there.

Best regards, Rainer.

@ Rainer
Okay, when I hover the cursor over the fields in the module control unit (ECU), comments appear. For one of these ECUs, for example, ECU 18, I saw the comment "Target value -2". I'm not at the car right now, and I'm not entirely sure anymore, sorry. I can't recall any explanatory comments for ECU 23.
"I was also thinking about providing more information than just "setpoint xy." MWB 18 + 23 describe the "electrical function" of the PDE. That could mean anything. For MWB 18, I find 3 values (0 / 4 / 6). Do those correspond to "on" and "off"? Why are there 3 values? For MWB 23, I'm reading both negative and positive numbers."
haithamina

The MWB 18 indicates the status of the valve, pump, and injector unit.
Possible values are 0; 4 (after pressing the accelerator), and probably also 128. However, I have never seen the value 128 myself.
All the other codes indicate an electrical problem with the PDE or a connection issue between the PDE and the MSG. For example, this common wiring harness. I saw the "6" code on your system. Does your engine run smoothly, or does it occasionally stutter or misfire?

The MWB 23 is the BIP (Begin of Injection) regulation. It refers to the delay between the activation of the PDE (Pre-injection Delay Element) and the actual start of injection. During this process, the current flow of the PDE solenoid valves is monitored by the MSG (Main System Controller). The target values for our 1.9 engines are between +100 and -100.
However, problems can definitely arise after the age of 60. Therefore, the memory can sometimes be empty even though there are already significant disruptions in operation.
The higher the positive value, the shorter the switching time. Conversely, the lower (or negative) the value, the longer the switching time.
High positive values indicate a faulty pressure drop element (PDE), while high negative values suggest problems with the fuel supply.

Read more here: [url] https://community.dieselschrauber.org/en/viewtopic.php?t=9888 [/url]

Here's some more information about the meaning of the numbers in MWB 18:/viewtopic.php?t=16802. So, nothing dramatic about the number 6 in your case.

Hello Steffen,
It's running perfectly and without any issues. Thank you for your explanations and the two links to further information!
haithamina

Now that I've finally recovered, I've carried out the tests:


Connecting the glow plugs to the positive terminal of the H7 bulb causes the lamp to light up every time.
Battery: Good, 12V voltage.
During the preheating phase, each glow plug connector has approximately 11.7 volts.

Apparently, everything is fine.

Repeated pre-glows at temperatures well below 0°C ultimately allowed it to start without any problems.

Nowadays, it starts up without any issues, even with just one pre-glow, at the current temperatures of 3-5°C. It wasn't like that in the beginning.

That's actually how it works.

Okay, the significant fluctuation in cylinder 3's output during idle speed control (2.99 mg), approximately 1 minute after a cold start, persists. Similarly, the subsequent unstable idle speed remains.

Since the spark plugs were last replaced 200,000 km ago, I'm considering replacing them to see if the idle air volume problem goes away (as per my theory in the previous post). They shouldn't be too corroded yet. Should the spark plug threads be lubricated with anything when reinstalling them (I've read something about copper paste)?

Thank you in advance.

Best regards,

Okay, please provide the German text you would like me to translate.

No copper paste.
"There's this paste from Beru. The exact name is: 'Glow Plug Grease GKF01'. I always use that. It's for preventing the glow plugs from seizing and ensuring they come out easily next time."
You don't have to tighten it that much. It works just fine like this. Remember not to exceed 17 Nm when tightening.