Golf 3 GTI TDI: Bad Starting Issues & Fixes

Hello, unfortunately, my search hasn't really helped me. My Audi A4 (AFN engine) has trouble starting when it's warm. The starter motor turns strongly, but the cold start is perfect. It starts worst of all when I turn it off at operating temperature and then try to start it again immediately; it can take up to 10 seconds before it starts! The glow plug system probably isn't the issue, but all the spark plugs have been replaced.

Here's a comprehensive article with numerous causes for starting problems, including those specific to engines that are already warm.
Have you already read it and checked everything?

Here is a comprehensive article with many possible causes for starting problems, especially when the engine is warm.
Have you already read it and checked everything?

Hello, yes, I've read that. The only thing that seems logical to me would be a faulty temperature sensor. Wouldn't air in the fuel system also become noticeable during cold starts? How can I test the temperature sensor with VAG-COM?

master_328 wrote:

Air in the fuel system would also become noticeable during a cold start, wouldn't it?

Yes, even mostly.

Quote:

How can I test the temperature sensor with VAG Com?

Call up a water bath with a specific temperature and log the data from the cold start to the operating temperature.
Check the logged temperature data for implausible values and short dips/spikes.

What happens during the warm-up phase?

What does 'warm rolling' mean? Does it mean starting the engine without using the starter motor? As I said, the starter motor is spinning very strongly, but I'll try that and read out the measurement block. Which one is it exactly? Is it easy to find? I'm not very familiar with the VAG-COM software yet!

master_328 wrote:

What does "warm rolling" mean? Does it mean starting without using the starter motor?

Yes, it's described in the technical article.

Quote:

As I said, the starter motor is spinning very strongly,

It's easy to be misled about the actual speed.
If it accelerates well in the fifth gear at around 30 km/h, the starter motor speed is probably still a bit low.

Quote:

but I'll try to read out the measurement block

. Useless when starting up.
When playing the organ, you can try logging "001" to see the speed (or RPM).

Hello,

I had the exact same problem with my AFN for about half a year until just last week. I checked all the wiring, resoldered connections, cleaned contact points, removed and lubricated the starter motor – all to no avail.

Last week, the starter motor finally gave up completely. When trying to start the car, all that happened was a clicking sound from the magnetic switch, and nothing else. Since I had to replace the starter anyway, I got a new one, an original Bosch part, for the painful price of 190 Euros!!!

Well, it's installed, the first start --> absolutely amazing! I should have done this a long time ago, but my wallet wasn't happy about the rather hefty price.

Since then, it has exhibited excellent cold-starting performance.

If you've tried all the solutions suggested in the articles and none of them work, then it probably just means you need a new one!


To the best of my knowledge, especially during a warm start, the starter motor's speed is crucial. Anything below 300 RPM will likely make it difficult to get the engine to start properly!

Greetings.
Okay, here's the translation:

"Achim"

AchimTZR wrote:

Since I had to replace the starter anyway, I got a new one right away...... Since then, it has exhibited excellent warm-starting behavior

.
...and that leads to the central question:
Could you distinguish between the sound/rotational speed of the old and new starter motor?

Hello,

I was very certain that I could distinguish between the two starters; the old one rotated *significantly* slower than the new one, there's no question about it!

The difference is extremely clear!

Greetings.
Okay, here's the translation:

"Achim"

AchimTZR wrote:

The old one spun MUCH slower than the new one, no question about it!

...and from that arises the next question:
Has Bosch changed anything about the starter motors, or why was the old one so weak, even though you tried to revive it?

For example, these devices no longer have stator windings; instead, permanent magnets are glued to the housing.
Could they weaken over time and thus also affect the starter motor?

Okay, so the temperature sensor seems to be fine. Since I usually drive long distances without stopping, this problem doesn't really bother me right now. I guess I'll just wait and see how much longer the starter motor lasts. I can't quite understand why the engine needs a higher RPM to start when it's warm; the engine naturally spins faster when the oil is warm, and it starts perfectly fine when it's cold!

master_328 wrote:

I don't understand why the engine needs a higher RPM to start when it's warm; the engine will spin faster anyway when the oil is warm, and it starts perfectly fine when it's cold!

Well, it seems like there's been a problem with the "Warmstart" software component in the AFN system...

You could also try disconnecting the water temperature sensor connector; this should allow the engine to start normally when cold because the engine control unit (ECU) will assume the engine is very cold.

...
I cannot understand why the engine needs a higher RPM to start when it's warm; the engine will spin faster anyway when the oil is warm, and it starts perfectly fine when it's cold!
Someone didn't properly study the technical articles; they only skimmed them...

Keyword: Compression in cold and warm engines!

Georg-TDI wrote:

Keyword: Compression at cold and warm engine!

Hi Georg,

The practice can , but also look different and master right:
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.
-> My post from March 4th; I'm somehow unable to create a direct link to the thread. At that time, I still had the AFN (Air Force Network).

By the way, I've elaborated on the "warm start puzzle" in more detail in the troubleshooting article.