Mit Standheizung erschwerter Kaltstart? | Posts 16+

naja....vorglühen kann man das nur auch nicht unbedingt nennen. die glühwendel geht kurz an und dann gleich wieder aus (ca. 1-2 sec. sehe ich sie vielelicht).

Well, as long as the check light comes on with every start, that's normal.

The poor starting performance is likely due to my experience with it.

-> Battery with decreasing capacity.
-> The engine thinks it's already warm, so it delays the injection timing and doesn't activate the glow plugs. However, the motor oil is still cold, indicating incorrect starting conditions.
->Empty diesel filter. However, this doesn't apply to you, as your SH has its own tank and doesn't actively draw fuel from the supply line to the engine.

->The engine thinks it's warm, so it delays the injection timing and doesn't preheat. However, the motor oil is still cold, which leads to incorrect starting conditions.


And that's exactly what I think it is! But I have no idea how to fix it. However, I can at least use VAG-COM to check if that's really the case...

I'm glad that at least someone shares my assumption .


best regards

Julian + BlauBaer wrote:

->The engine thinks it's warm, so it delays the injection timing and doesn't preheat. However, the motor oil is still cold, indicating incorrect starting conditions.

And why should the oil temperature be crucial for the starting process?

In my understanding, the combustion chamber temperature and possibly the diesel temperature play a primary role in the starting behavior. The diesel temperature should be independent of the supplementary heating system (SHS). In contrast, the combustion chamber temperature is likely to be close to the engine block temperature, and therefore close to the water temperature.

The cold oil will indeed flow through the engine block after starting and cool it down, but I'm not sure that the cold oil is supposed to affect the combustion chamber temperature during startup . I need some clarification on how you arrived at that statement.

PS: Mine starts up better after the STH has been running than it does without preheating.

Regards,
Sure.

Here is the translation of the text from German to English:

"Guste" means "gust" in English. It refers to a sudden and strong gust of wind.

The cold oil will indeed flow through the engine block after starting and cool it down, but I'm not sure that the cold oil is supposed to affect the combustion chamber temperature during startup . I need some clarification on how you arrived at that statement.


Simply put, cold oil has lower viscosity than warm oil. The resistance that the oil pump has to overcome is higher with cold oil, but this is taken into account during the starting process (e.g., engine angle, injection quantity), and a partially warmed engine falsely suggests to the MSG (Motor Steuergerät - Engine Control Unit) that it is warmer than it actually is.

'With my previous ALH engine, I also experienced this issue where the engine would start but run poorly. However, troubleshooting was unsuccessful because the main temperature sensor indicated a warm engine, but only half of the engine actually warmed up, and the starting parameters were altered. As far as I recall, the injection timing was about 2° later, and the fuel injection quantity was slightly lower. The pre-glow/post-glow function was completely disabled.'

Julian wrote:

Ganz einfach, kaltes Öl ist weniger viskos als warmes. Der Widerstand, den die Ölpumpe überwinden muß ist bei kalten Öl höher, beim Startvorgang (°Winkel, Einspritzmenge) wird dies aber berücksichtigt und durch einen halbwarmen Motor dem MSG fälschlicherweise vorgegaukelt.

So, with a higher load on the oil pump, do you think a smaller timing angle and/or a larger amount of fuel is needed?

It is understandable that the engine requires more effort to turn and therefore rotates slower, due to the lower oil viscosity. However, the engine speed is taken into account in all relevant parameters (both quantity and angle) of the engine control unit (ECU), and is accordingly compensated for.

It's understandable that the motor requires more electrical energy to achieve or maintain the same speed under a higher load. However, even with a higher load, there should still be enough electricity for ignition; otherwise, the motor wouldn't reach its operating speed. At least, this isn't how it works in my experience. Either the diesel fuel ignites and provides enough power to bring the engine up to speed, or it doesn't ignite at all. I find it strange that it exhibits behavior similar to older engines, where you could tell they were trying to start but couldn't quite manage it. In my experience with a TDI, there are only two states: either it starts, or it doesn't. I haven't encountered any intermediate stages (assuming no defects).

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

"@ BlauBaer"

Have you checked your dynamic start-up settings?

It's possible that it's running outside of the specified tolerance, and under those circumstances...
difficult to start.

Simply put, cold oil is less viscous than warm oil. The resistance that the oil pump has to overcome is higher with cold oil, but this is taken into account during the starting process (e.g., engine angle, injection quantity), and a partially warmed engine falsely leads the MSG (presumably a control module) to believe it's warmer than it actually is.


However, that is not the reason for advancing the start of injection.

It's solely about the ignition delay that occurs when the cylinder walls are cold.

If a partially warm engine is harder to start than a completely cold one, it usually points to a weak battery or starter motor (or, in the case of older vehicles, wear and tear on the fuel pump).

When the engine is cold, the amount of fuel injected during startup is significantly increased (mainly due to the delayed ignition and because, even in a diesel engine, fuel deposits on the combustion chamber walls during startup).

If the starter motor cannot reach the minimum speed (which cold oil certainly contributes to), very little fuel will be injected into the cylinders. A possible check is to push-start the car. If it starts immediately then, you should check the starter motor and battery along with their cables.


CU Gremlin.

Hello,

Regarding your question about remote control functionality:

The easiest way is to simply open the pre-heating function and connect the signal in parallel with the instant heating button. The timer will then take over the rest.

Here's how I did it: I simply used my old phone and tapped into its vibration motor. This motor, just like the instant heating button, is connected to ground. Then, I connected a charging cable (absolutely necessary to ensure a common ground between the car and the phone) to the ignition positive terminal, and that's it.

It has been running perfectly for several weeks now.

I hope this helps you in some way.

Best regards,
sLindi