hand-made Start-Stop / generelles Startverhalten | Posts 48+

Hello Martin,

The points you mentioned can definitely be logged. However, I fear that the temporal resolution of Log + DMM will negate any potential insights.

But you could try running a quick log, maybe you'll see something.

Regarding different power consumers, I would attribute the variations less to the piezoelectric transducers and more to potential differences between model years/engines. For example: Do the xenon headlights stay on when starting the car? What kind of bulbs (H7?) does your sister's car have? How do the glow plugs behave during startup in both engines? Which other devices remain connected or are switched off? (These are just ideas on my part; I have no idea whether there are any real differences.)

Best regards,
Guste.

The cars are very similar.
- both MJ 07
- BMR vs BMP
- Xenon vs. H7
- RCD510 vs RCD500
- Sound system vs. no sound system.
- AHK vs. no AHK.
- No rear airbags.
Those were the differences.

Yesterday, both starts (BMP at 1 degree Celsius, BMR already at 10 degrees Celsius) showed very similar voltage drops during the start-up phase.

However, the BMP is reading 14.8 volts, while the BMR is reading 14.1 volts.
The logged generator load was also higher in the BMR case, although it traveled a different route.

Who actually controls the Lima?
I'm going to take a look at BNSTG 030.

m;

dieselmartin wrote:

Who actually controls the Lima? I'm going to take a look at BNSTG 030.

LiMa taxes?

The battery management system (BMS) is internally regulated and provides a fixed voltage (provided you are not operating at the maximum load limit). Furthermore, it outputs the signals L (charging indicator light / status indicator) and DFM (load signal, PWM).

Nothing is controlled from the outside.

If the battery terminals are indeed producing significantly different voltages, then either the load and resulting voltage drops between the alternator (LiMa) and the battery are considerably different, or there is a different resistance between them. Alternatively, different LIMAs (linear motor drives) or different controllers could also be installed.

Regards,
Guste.

I think I'm giving up.

- The LIMAS codes are identical: 021 903 026 L.
- When measuring with a multimeter in open-circuit mode, the BMR now showed a higher voltage than the BMP (with VCDS, it was always the other way around).

The startup behavior appears to be caused much more by the different applications than by voltage and current fluctuations.
The BMP has significantly more torque in the LL (Low Range), while the BMR seems to prioritize smoothness and stability.

Spontaneous starting but jerky acceleration is likely just a combined characteristic of the 0420 software for the 03G 906 018 EM... and I've now updated to software version 4369.

m;

Hi Martin,

Regarding your batteries: My car battery (6 years old) in my Golf (AXR) always shows ~12V when the engine is off (this was also the case when it was new). If I draw about ~1A from the battery using a charger, I can easily get a reading of 11.5V (at 30°C in the summer). Despite this, the Golf started without any problems last winter, even at -19°C and after being stationary for 2 weeks (with interior monitoring).
Generally, I agree with anyone who, in your case and mine, says: "The battery is defective because the voltage is noticeably low." I find it almost reassuring that you also have one of those "odd batteries."
What I've noticed is that when I turn on the ignition and buckle my seatbelt *before* starting the engine, it starts much faster. And that's despite the preheating indicator having long since gone out.
Have you ever tried that? What do your spark plugs look like? Are there any differences between your two engines? Do candle types reach their operating temperature faster?

Regarding your error message after the engine stall: I wouldn't overemphasize it. If you stall the engine and then quickly restart it, it can sometimes lead to unusual effects. If this doesn't happen during a normal startup, I wouldn't worry about it.

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

Mephisto wrote:

What I've noticed in my own experience: When I turn on the ignition and buckle my seatbelt before starting the engine, then the engine starts _much_ faster. And that, even though the preheating indicator has, of course, been off for quite some time.

Absolutely. Just because the preheating indicator is off doesn't necessarily mean that preheating isn't still happening. Just turn on the interior light, turn the ignition on, and by observing the behavior of the interior light, you can see when the glow plug function truly stops. Or simply be quiet and listen to when the glow plug relay clicks.

The BMR (and possibly also the BMP and BLS) no longer have a preheating relay.

The ceramic candles are activated in a staggered and pulsed manner.
This allows them to be monitored, and since the candles are powered by 4 volts, they don't all draw power from the battery at the same time.

Thanks to the 16V configuration, they are mounted inside the head, so I won't be able to just "quickly" remove them.

m;

Martin, perhaps that was your crucial tip: BMR = 16V, BMP = 8V. So, twice as many valves, which also need to be activated during the starting process.

That might be a bit more difficult.

Nevertheless, I would continue to investigate further only if the starting behavior becomes a problem.

Regards,
Guste.

Well then:

(1) In the past, it used to start immediately.
(2) Last winter, he was already having a lot of trouble - there were a few mornings when I wasn't sure he would start up at all, but he eventually did.

I only have the BMP today, so I'm going to record a video of the launches and then put the batteries back.

m;

Hi,

TDI-GTI-4-Motion wrote:

Or simply be quiet and listen for when the preheating relay clicks.

...or simply start with a small amount of gas, and you can even feel when the afterglow is ending .

@Martin:

Quote:

(1) previously, it would start immediately. (2) Last winter, he was already having a lot of trouble - there were a few mornings when I didn't think he would start up anymore - but he eventually did.

If the glow plugs are located under the valve cover, they are diagnosable. So, you've probably already checked using a diagnostic tool to see if they are functioning. However, the question is: what happens if the gap between a glow plug and the cylinder head is blocked, and the glow plug transfers heat to the cylinder head? In that case, the diesel engine might not ignite at the first top dead center (TDC), but perhaps only at the 2nd, 3rd, or 4th TDC, depending on how many glow plugs are affected. For situations exactly like these, Beru offers a friction gauge...

What about air bubbles in the fuel?

Regards,
Sure, here is the translation of the text from German to English:

"Micha"

What exactly is Beru "releasing" in this case? Candle or hole in the head?
Does that require taking the head off?
Of course they can be diagnosed – they are carefully monitored.
Don't all EURO4 trucks do that?
(That's why Golf BLS owners are always complaining that theirs is about to break down, which isn't actually the case.)

However, even when it's not glowing, it doesn't turn on as readily as the mPDs do.

m;

Mephisto wrote:

...or simply start with a little gas, and you can even tell when the afterglow is ending

.
No, I didn't mean the afterglow, but the preglow. That's why I said, just turn on the ignition without starting the engine. It glows for a significantly longer period than the indicator light shows.

Quote:

It preheats for a significantly longer time than the indicator light suggests.

That's the pre-start glow. The GSKs are kept "warm" with a reduced duty cycle.
Similar to the "interim glow," which there are rumors about but which I haven't seen activated (via a software switch) on any PD (plasma display) I've worked on.

vwSchrauber wrote:

This is the ready-to-start glow. The GSKs are kept "warm" with a reduced duty cycle. Similar to the "interim glow," which there are rumors about, but which has not been activated (software switch) on any PD (power distribution) unit that I have worked on.

Just to clarify, my statement doesn't refer to Martin's Passat, but to older TDI models. I've observed this issue, for example, on my own ACV engine. There's nothing about PWM here. It's only permanently on or off.

Quote:

There's nothing about PWM here. icon_wink.gif It's just on or off.

PWM is basically "just on and off" , but we understand.

It should be clear to everyone here that you can't rely on the information displayed in the AI system.
Only the 8 bits in 012.1, specifically the "glow status" bits, provide meaningful information.

I've already modified the LBL so that you can directly see what each bit means within VCDS.

m;

Quote:

Just to clarify, my statement doesn't refer to Martin's Passat, but to older TDI models. I've observed this, for example, on my ACV. There's nothing about PWM here.

It's just on or off.

Oops, I probably overlooked that. I was thinking of BRE, BMP, BLS, etc.