ALH Engine: Unusual Starting Problems

Hello everyone.

Here's the scenario during the first engine start of the day: (and only during the first one!)

When I turn on the ignition, wait 5-6 seconds, and then start the car, the starter motor pulls the voltage down enough to activate the central locking system. (However, the starter motor doesn't run for very long before the car starts).

When I turn the ignition on, wait 10 seconds, turn the ignition off, then turn it on again for 10 seconds, and then start the car, I can hear the voltage drop slightly, but the car starts normally without the central locking engaging.

Otherwise, there were no issues with the startup procedures.


The battery is the original one from the factory, and all four glow plugs are working properly (2 were replaced just a few days ago).

The vehicle is a Golf Variant, manufactured in June 2000.

I'm at my wit's end and hoping someone here can give me a good tip that explains this "curiosity."

Thank you very much.

Pre-glow heating. I should check the configuration file to see if this is enabled for the ALH.

Speculation: Your battery is so weak (high internal resistance) that the voltage during starting, without the glow plugs activating, is just barely enough to prevent the central locking system from malfunctioning. When the glow plugs activate, the threshold is exceeded.

Diagnosis: Connect a second battery (from another vehicle) and see if the behavior changes.

Do you happen to know your engine control unit (ECU) number? It should start with 038 906 012 (or 018 for that model year) followed by two more digits.

vwSchrauber wrote:

Do you happen to know your engine control unit number? It should start with 038 906 012 (or 018 for that model year) followed by xx.

Let me quickly check that.

Shouldn't the problem actually be the opposite, since some voltage would presumably be consumed during the glowing process?


Edit:
Okay, according to VCDS, the control unit installed is 038906012M.

I just checked an ALH file, and it should be enabled. I don't have the 012M version, but it shouldn't be too different.

Quote:

Shouldn't the problem actually be the opposite, since some voltage would likely be consumed during the glowing process?

If the heating element is activated simultaneously with the start-up, the voltage drops too low. However, the heating process during start-up is not indicated by the indicator light.

Quote:

The battery is the original one from the factory, and all four glow plugs are working properly. (2 were replaced just a few days ago)

If it's still the first battery, I would proactively replace it to avoid having to troubleshoot a problem later.

@BM:

cheap troubleshooting:

Quote:

Diagnosis: connect a second battery (from another vehicle) and see if the behavior changes.

The software of the control system does not cause the behavior; it explains it.

Okay - old cables and connections (especially ground connections) should be checked and ruled out beforehand.

vwSchrauber wrote:

I just checked an ALH file, and it should be enabled. I don't have the 012M, but

it shouldn't be too different.

Starting on 09/03, the replacement part is 038906012GK.

vwSchrauber wrote:

Quote: Shouldn't the problem actually be the opposite, since some voltage would likely be consumed during the glowing process? If the heating element is activated simultaneously with the start-up, the voltage drops too low. However, the heating process during start-up is not indicated by the indicator light.

But if it's supposed to glow for 2 x 10 seconds, shouldn't it consume more power/have consumed more power than if it only glows for 1 x 5-6 seconds? And if that's the case, wouldn't it start worse when glowing for 2 x 10 seconds?
But it performs worse with a 1x6 second setting than with a 2x10 second setting... (that's why I'm so confused).

BM wrote:

Quote: The battery is the original one from the factory, and all four glow plugs are working. (2 were replaced just a few days ago) If it's still the first battery, I would proactively replace it before you start searching for a problem.

Correct, that is the first battery.

vwSchrauber wrote:

The software of the control system does not cause the behavior; it explains it. Okay - Old cables and connections (especially ground connections) should be ruled out beforehand.

Just a reminder:

It only happens during the very first start of the vehicle. After that, I have absolutely no problems starting it throughout the day. Therefore, I'm simply ruling out corroded cables.

Quote:

@BM: cheap debugging: "Quote:" Diagnosis: Connect a second battery (from another vehicle) and see if the behavior changes.

It's possible, but I consider it a temporary fix for an 8-year-old battery. It's only a matter of time before it completely stops working.

Quote:

But if I were to glow for 2 x 10 seconds, shouldn't it consume/have consumed more power than if I only glowed for 1 x 5-6 seconds, and therefore would it start worse when glowing for 2 x 10 seconds? But it performs worse with a 1x6 second interval than with a 2x10 second interval... (that's why I'm so puzzled).

Okay, let's go slowly and in detail:

- Glow for 5-6 seconds: 4 glow plugs, each at 10 amps, plus 1 starter at 170 amps = 210 amps.
- 10 seconds: The pre-glow function is already disabled, so only 170 amps are available for the starter.

Alternative test method: Disconnect the connector for the CNC control unit, including the coolant heater glow plug. Then, try starting the machine. It may not start immediately, but the central locking problem should not occur.

Otherwise: the GSK (heating elements) can be "partially defective." This means that the control coil glows instead of the heating coil. We've seen this happen several times. A GSK with such a defect will draw 50-100% more power. If two of your GSKs have such a defect, the preheating current could reach 60 amps, which would bring the total to 230 amps instead of 170 amps.

"On my Passat 3B (summer car), the central locking system would always make a whirring noise when I took it out of winter storage, and I was sometimes too lazy to plug in the battery charger."

But, as BM already wrote: start with the battery .

Okay, then I'll try it tomorrow morning without the 7 candles.

It probably sounds like a weak battery.
(Damn, I actually wanted to hold off on putting anything else in until April, because that's when the 1T2 will be finished.)

I will report.