TDI Cold Start Problems: Audi A6 5-Cylinder

Hello.

'For some time now, I've been having a problem with my Audi A6 C4, manufactured in 1996 (2.5L, 140 hp, AEL engine, 165,000 km). When the engine is cold, it starts poorly. I have to crank it for a while. Sometimes it only starts on the second attempt. Once it's started and still somewhat warm, it starts immediately.'
Does anyone else experience this problem, and does anyone have any idea what might be causing it?

I hope this question hasn't been asked and answered a thousand times already. I couldn't find anything relevant in my search.


Best regards,

Hello,
I would investigate the possibility of adjusting the injection timing.
Could the starting problem be related to a recent timing belt replacement? If so, the injection timing may not have been set correctly during the procedure.
Otherwise, there's also the preheating system, which is unlikely to be relevant given the current weather conditions, or air bubbles in the fuel lines.

Regards,
Andy.

Hello,
I would investigate the possibility of adjusting the injection timing.
Could the starting problem be related to a recent timing belt replacement? If so, the injection timing may not have been set correctly during the procedure.
Otherwise, there's also the glow plug system, which is unlikely to be the issue given the current weather conditions, or there might be air bubbles in the fuel lines.

Regards,
Andy

Hello.

The last timing belt replacement was 1 1/2 years ago.
Air bubbles?? Hmm, I'll try replacing the fuel filter.

What about the fuel injectors? Could they be the cause of the problem, or is it unlikely? Besides the cold start issues, the car runs great.

Best regards,

Thinking...

1) If there's air in the system, the engine will misbehave, not just during the cold start phase.

2) Leave the diesel filter in; it has nothing to do with the cold start phase.

3) The start of injection will be correct; otherwise, the engine would exhibit problems in other ways, not just during the cold start phase.

4) Replace the coolant temperature sensor, and that should fix it, as it's closely related to the cold start phase.

Julian wrote:

3) The start of injection will be correct; otherwise, the engine would exhibit problems in other areas, not just during the cold start phase.

That's not the case. I'm just referring to Hähnlein's well-known mega-thread.

1) If there's air in the system, the engine will misbehave, not just during the cold start phase.



Hi,

A car engine operates in its cold start phase when it has cooled down due to prolonged inactivity. It is precisely during this phase that even the smallest leaks in the fuel system, caused by air entering, become significant. We have already seen numerous cases of various leaks between the ESP (Electronic Stability Program) and the fuel tank, which led to starting problems.

Apart from that, the coolant temperature sensor is, of course, also a likely culprit...

Regards,

Andy.

Please tell me your mileage.

The injectors may be leaking.
Can the pressure relief valves on the pump head be defective?
Can the start of the injection be adjusted?
Coolant sensor.
Starter? Battery?

Could you please write down your mileage?

The injectors may be leaking.
Can the pressure relief valves on the pump head be defective?
Can the start of the injection be adjusted?
Coolant sensor.
Starter? Battery?

165,000 km

Battery is 3 months old.


Now that it's warmer, with an outside temperature of around 17°C, it starts up better. So it seems that the temperature range between approximately 7°C and 15°C is causing problems. I'll try to have my mechanic read the car's diagnostic system in the next few days.

Best regards,

Honk wrote:

Now that it's warmer, with an outside temperature of around 17°C, it starts up better. So it seems that the temperature range between approximately 7°C and 15°C is causing problems. I'll try to have my mechanic read the car's diagnostic system in the next few days. Regards

Hello!

That, in turn, sounds more like a preheating system!

Best regards, Christo.

christo wrote:

Honk wrote: Now that it's warmer, with an outside temperature of around 17°C, it starts up better. So it seems that the temperature range between approximately 7°C and 15°C is causing problems. I'll try to have my mechanic read the car's diagnostic system in the next few days. Regards Hello! That, in turn, sounds more like a preheating system! Best regards, Christo

Hi,

For TDIs, the glow plug system is not necessary for starting the engine when the temperature is above approximately 5°C.

Best regards, Rainer.

Hi,

I would like to test the start of the injection.
He is definitely a candidate (based on my own experience).
In my case, it was due to the timing belt replacement.
If it's been a while since your last injection, and you suspect the problem might be related to the injection process, you should check if the device has been adjusted unintentionally.