Golf IV TDI 66KW ALH Warmstartprobleme

Hello,

for some time now, my vehicle has been starting very poorly when warm.
In the cold, it only takes about 1 second, but when the engine is warm, I have to keep the starter engaged for about 5-6 seconds before the engine starts.
Mileage: 105,000 km
Year of manufacture: 07/98
Engine code: ALH / 66Kw
The timing belt was replaced at 90,000 km, but this problem was also present before. Diagnostics have never shown anything.
Regards,
mJudge
[color=darkred]

Hello!

I had the same issue with my ALH. Let's check the battery first, the starter motor also needs to accelerate the engine by about 300 rpm so that the fuel pump control can work.

I had the same issue a few weeks ago, and the battery then died shortly after. With the new battery, the starting problems were gone.

VW has a battery tester that measures the starting energy (cold test current). Let's have that checked and replace the battery if necessary.

If the timing belt is misaligned, there is usually an entry in the fault memory and some loss of power.

Hello Julian,

but the battery issue should apply both in cold and warm conditions, right? Mine starts well in cold conditions, but not in warm ones.

Best regards,
mJudge

No. Mine started perfectly in the cold, but not in the warm. Since the coolant temperature sensor provided plausible values, it couldn't be that. The injection timing was also correct; the engine started with long, sustained engine sounds (not too long, with pauses).

[quote="Julian"]No. Mine started perfectly in the cold, but not in the warm.[/quote]
Hi Julian + all,

this observation is still a TDI mystery for me (it is for my car too, but only slightly).

IMO, every engine will start more sluggishly the colder it is.
If the starting speed for a clean (cold) start is sufficient for a specific vehicle, it should be
[b]That's all [/b] I need :

Maybe the right experts can solve this (apparent) contradiction?

Hm, maybe because the starter gets warm and therefore has less efficiency?

In the cold state, more (longer) fuel is injected than in the warm state. That's probably why you need more RPM to ignite the mixture. Is that it?

[quote="Julian"]Maybe because the starter gets warm and therefore has less efficiency?[/quote]
Here's the translation:

This is how it works. I have now re-taught my ALH 98 to warm start. After all the possible attempts, I read a tip in this forum about the sluggish starter - and I immediately thought of a warm-starting problem that I had solved years ago: IHC 214D tractor, a wonderful piece from 1961, but it wouldn't start when warm. I did everything (adjusted valves, corrected fuel injection timing, replaced fuel injectors, etc.) until I discovered that some copper wires were no longer properly pressed in the starter rotor. After replacing the starter, it runs perfectly to this day. Apparently, the starter speed decreases when warm due to the increasing resistance in the copper windings.

Back to my piece: starter removed, disassembled (looked very good despite the recent intensive starting attempts), moving parts (planets, etc.) cleaned and re-lubricated, and the connections for the main and positive cables were cleaned and reconnected.

I immediately felt a certain improvement. However, this success encouraged me to continue researching, and now I have soldered the connections for the main and positive cables (of course, they were just crimped). Now everything is like new. I can now confidently start the engine even after short stops.

I think the gradually decreasing starter speed is also caused by the possibly weakening permanent magnets in the starter (stator).

Best regards,
Andreas

[quote="98er_alh"]Now everything is like it was on the first day. I can also start the engine again after short stops. [/quote]

Hi Andreas,

how long does it take for your engine to warm up before you start it?

Mine sometimes takes about 1 second.
I think the gradually decreasing starting speed is also caused by the potentially weakening permanent magnets in the starter (stator).
As far as I know, the stator's magnetic field is also generated purely electrically
Or are there actually series with permanent magnets

[quote="ulf"][quote="98er_alh"]Now everything is like it was on the first day. I can also start the engine again after short stops. [/quote]

Hi Andreas,

how long does it take for your engine to warm up after being turned off?

Mine sometimes takes about 1 second.
[quote]I think the gradually decreasing starting speed is also caused by the weakening permanent magnets in the starter motor (stator).[/quote]
As far as I know, the stator's magnetic field is also generated purely electrically
Or are there actually series with permanent magnets
So, before I would warm up for up to 20 seconds and sometimes take several attempts – it had significantly deteriorated since November. Now, it sometimes takes a second, and sometimes it almost starts on its own (like my good GII 54PS with 400,000 km).

The stator definitely has magnets, like a toy motor. I was wondering why the starter was so light. I had assumed that I would normally have a series-connected motor for the purpose, but the magnets are definitely 3 cents cheaper than the proven alternative. On the other hand, you're making me think about possibly finding starters with a "copper stator" to upgrade if the deterioration occurs again.

Best regards, Andreas

Hello,

Just to inform you, the starting speed would initially increase with a weakening permanent magnet.

Best regards,
Christian
I think the gradually decreasing starting speed is also caused by the weakening permanent magnets in the starter (stator).

but only without excessive load on the engine ;-)

Under load, a weaker magnetic field initially affects the transmitted torque... it is logically also weaker. Therefore, the engine cannot reach the desired speed under load.

CU Gremlin

Hi,

Although I'm not a professional mechanic, reading the responses makes me consider two possible problem scenarios.

1. Cold vs. Warm:
It seems that the cold engine requires a different injection method than the warm engine.
Could we try simulating a colder temperature for the warm engine (NTC PTC ??), just for testing?

2. Starter RPM:
Starting a warm engine with a starter cable will result in a higher RPM due to the better voltage.

Just a thought.

BERT

Okay, hier ist die Übersetzung des Textes, wobei HTML-Tags, BBCode-Tags und URLs unverändert bleiben:

[quote="BERT"]
Hi,

ich bin zwar kein Profi, aber wenn ich die Antworten so lese, kommen zwei Problemvarianten in Frage.

2. Anlasserdrehzahl:
Ein warmer Motor mit einem Anlasskabel starten. Die Anlasserdrehzahl ist dann aufgrund der besseren Spannung höher.

Naja, das war nur eine Idee.

BERT
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
I realized that the incorrect starting RPM was a problem when I tried starting the engine by rolling it over. This worked immediately. I also like the idea of using jump leads. The key is to slightly increase the starting RPM. The tricky part is that the engine starts normally (quickly) and you don't notice if it's missing 50 RPM. Also, you won't notice a drop in the idle RPM if you run the engine for a while, so you'll be looking in all the wrong places.

Andreas

Hello

It's understandable that you can "tune" a starter by reconnecting internal connections, cleaning, and lubricating.

It's also clear that the willingness to start decreases rapidly with the starting speed due to increased leakage, lower injection pressure, and increasing compression loss.

However, I still don't understand why the TDI engine often hesitates to start after a warm-up, even though it starts well when cold:

Shouldn't everything be lost in a diesel engine if it doesn't start immediately?

IMO, the optimal ignition conditions should be around the 2nd compression, when the starter has just fully brought the engine to speed. After that, the starting speed should gradually decrease as the starter winding continues to heat up and the battery also starts to fail.

Therefore, the conditions are actually getting worse the longer the engine is "geholt". Nevertheless, the engine usually starts eventually - and I'm wondering:
[b]why bother at all[/b]


Initially, I thought that the accumulation of unburned diesel in the cylinder heads with each unsuccessful injection would increase the compression ratio, allowing the engine to start even with a low RPM.

However, rough calculations suggest otherwise:
A generous estimate of 20 mm³ per stroke would fill the approximately 24 cm³ combustion chamber of a 1.9 engine by 0.08% per injection. Before a truly start-improving compression increase could be achieved (at approximately 4 injections per second and cylinder), the starter and/or battery would likely have given up long ago.

Or should the EDC gradually increase the injection amount during the starting process until the engine eventually starts? Then, it should happen much faster, instead of stressing the driver, battery, and starter for up to 10 seconds or more??

Or does the compression heat only initially dissipate significantly into the surrounding material (as mentioned above), and while the upper layer of material heats up further with each compression, the peak temperature can increase accordingly, effectively "overcompensating" for the declining RPM?

In my tractor, the problem definitely lies in the late injection timing. While the fuel injector is slightly opened during warm-up, interrupting its electrical connection (earliest possible injection start) did not significantly improve the warm-start.

Perhaps I am simply missing something. It would be great if someone could help me . . .

[quote='ulf']
It's definitely not my tractor that's having problems with starting too late. While the fuel injector control valve opens slightly during the warm-up, interrupting its electrical connection = the earliest possible fuel start did not clearly improve the warm-up.

Maybe I'm just missing something. It would be great if someone could help me...
Okay, I understand. Please provide the German text you want me to translate. I will translate only the readable text, leaving the HTML tags, BBCode tags, and URLs as they are.
Now you must remember that the start of injection or more precisely the position of the fuel injector for the start of injection depends on the pressure in the pump interior. And this is proportional to the pump speed. That's why the minimum speed of 300 (starter) or 150 (pump for 4-cylinder) is prescribed. Otherwise, the pressure generated by the pump is not sufficient to control the injection start sufficiently early. To find out, you would have to measure the interior pressure at start.

The fact that it might eventually start could be due to the fact that the wings of the fuel pump do not fully close and that, after a long struggle, they eventually make good contact with the wall and the pressure increases. At normal operating speeds, this is not a problem (centrifugal forces). This is a possible scenario...

CU Gremlin

Hi everyone,

I think the suspicion is going in the right direction. If he injects fuel and it still doesn't start, then when it does start later, he would definitely have a large cloud of smoke coming from the exhaust.

I don't think the fuel pump can run so slowly during starter operation that a diesel puddle accumulates on the piston.
Insufficient compression wouldn't actually be the cause either. Then he would also have to blow out a thick cloud of smoke.

Maybe we should try a test: cool the ESP with a water hose while the engine and starter are hot, and then see if it starts better.

Best regards,

Eike