Only buy from reputable sources. Annoyingly sometimes the genuine Bosch (or even Audi) branded items are actually made in China which makes my blood boil. Same as BREMBO brake parts - WTF. I digress.
Fuel Rail/System Pressure Low 2005 Audi A8 D3 6.0 W12
- Thread starter Amiran Tsanava
- Start date
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
My apologies for such a long delay...
I decided to repair the alternator and had to leave the car at my friends shop.
The result was amazing.
Replaced the relay/regulator inside it and it became like new.
Lights stopped flickering and I think the whole car became better.
By the way, my friend replaced EVAPs with used (but from 100% working vehicle) ones and I have just connected back the battery, started the engine and drove home.
Here's log depicting engine ECU 2 while I was driving home:
0002-LOG-11-01D-02A-032-705-73F
noticed that the start was pretty rough with a bit excessive vibrations (like before, I guess) but then it became so smooth as an electric vehicle (!!!) before reaching warmed up temperatures around 109°C and by the way... I don't think the temperature should be traveling up to 109°C-112°C and fans turning at max speed in traffic jams without any load on the engine.
All can be spectated very well using the log.
I'll do the same log for ECU 1 after the engine completely cools down. Tomorrow may be.
I decided to repair the alternator and had to leave the car at my friends shop.
The result was amazing.
Replaced the relay/regulator inside it and it became like new.
Lights stopped flickering and I think the whole car became better.
By the way, my friend replaced EVAPs with used (but from 100% working vehicle) ones and I have just connected back the battery, started the engine and drove home.
Here's log depicting engine ECU 2 while I was driving home:
0002-LOG-11-01D-02A-032-705-73F
noticed that the start was pretty rough with a bit excessive vibrations (like before, I guess) but then it became so smooth as an electric vehicle (!!!) before reaching warmed up temperatures around 109°C and by the way... I don't think the temperature should be traveling up to 109°C-112°C and fans turning at max speed in traffic jams without any load on the engine.
All can be spectated very well using the log.
I'll do the same log for ECU 1 after the engine completely cools down. Tomorrow may be.
Last edited:
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
So, here's cold start for engine ECU 1:
0001-LOG-01-01D-02A-032-705-73F
and here's the engine ECU 2 as well, because I had a nice long drive and felt the car behaving so good and so smooth I couldn't help myself to record this:
00002-LOG-11-01D-02A-032-705-73F
checked the coolant temperature as well and it was not more than 105°C
I'm about to start thinking that the temperature has some connection to it all as I can observe the car seems smoother when the coolant temp doesn't exceed 105°C-106°C
At the end, I deleted all the codes stored into ECU 1/2 and reseted adaptation and plan to repeat the ride in the nearest future.
Any thoughts?
0001-LOG-01-01D-02A-032-705-73F
and here's the engine ECU 2 as well, because I had a nice long drive and felt the car behaving so good and so smooth I couldn't help myself to record this:
00002-LOG-11-01D-02A-032-705-73F
checked the coolant temperature as well and it was not more than 105°C
I'm about to start thinking that the temperature has some connection to it all as I can observe the car seems smoother when the coolant temp doesn't exceed 105°C-106°C
At the end, I deleted all the codes stored into ECU 1/2 and reseted adaptation and plan to repeat the ride in the nearest future.
Any thoughts?
ECU1 logs visualised below. There is a brief excursion of lambda correction above -20% at the very start for some odd reason but you can now see purge valves getting activated and no significant effect on lambda values. Wondering if the transients are a result of a bad connection somewhere in lambda wiring maybe - I would continue to monitor and log every once in a while on the same test route so you have some baseline behaviours to compare with should things ever get weird again !
and ECU2 log visualised below:
and ECU2 log visualised below:
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
Thank you so much.
I'll proceed with monitoring and see what changes.
Could you please explain to me where are these components located and how do they operate?
1. Tank Ventilation Valve?
2. Activated Charcoal Filter?
3. How is relative fuel portion reading calculated?
4. EVAP emissions solenoid valve - I already know those are the two solenoid valves (under the hood) I have just replaced.
I'll proceed with monitoring and see what changes.
Could you please explain to me where are these components located and how do they operate?
1. Tank Ventilation Valve?
2. Activated Charcoal Filter?
3. How is relative fuel portion reading calculated?
4. EVAP emissions solenoid valve - I already know those are the two solenoid valves (under the hood) I have just replaced.
Let me try and provide a brief explanation but you will find more details via your favourite search engine or AI chatbot.
1. TEV is a component of an extended emissions control system for helping ensure that high levels of fumes do not build up in the fuel tank. It works alongside the EVAP system but is not fitted to all VAG vehicles.
2. The ACF is part of the EVAP system and will be on your W12 - think of it as primary treatment of the evaporative fumes from the fuel tank which are held there temporarily before the EVAP purge valves let them escape into the engine in a controlled manner. If you follow the hoses from your EVAP valves they will lead you to the ACF. It's not a very exciting component that's for sure. Some cars it's tucked away in the engine bay, while in others it can be hiding in a rear wheel arch (typically near the fuel filler cap).
3. That'll be one of the bazillion calculations made inside the ECU as part of the emission control system.
1. TEV is a component of an extended emissions control system for helping ensure that high levels of fumes do not build up in the fuel tank. It works alongside the EVAP system but is not fitted to all VAG vehicles.
2. The ACF is part of the EVAP system and will be on your W12 - think of it as primary treatment of the evaporative fumes from the fuel tank which are held there temporarily before the EVAP purge valves let them escape into the engine in a controlled manner. If you follow the hoses from your EVAP valves they will lead you to the ACF. It's not a very exciting component that's for sure. Some cars it's tucked away in the engine bay, while in others it can be hiding in a rear wheel arch (typically near the fuel filler cap).
3. That'll be one of the bazillion calculations made inside the ECU as part of the emission control system.
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
Back with one more LOG record for ECU Engine 2
This time I made 2 LOGs (but VCDS saved them in one file, I don't know why) which depict cold start, a short ride in a traffic jam and hot ride in a traffic jam mostly stationary because of the clogged traffic.
I have removed MAFs from the list (because they seem to be perfectly fine) and added coolant temperature and throttle position.
My observation is that the engine behaved quite well before it achieved the fully working temperatures. Afterwards it started to shift revs up to 800 RPM from time to time, with no reason (visible for me) for quite a long periods and returning to normal 640 RPM for a very short moments during the whole test.
00022-LOG-11-01F-022-034-705-73F
I'll perform the same test with ECU Engine 1 in the nearest future.
This time I made 2 LOGs (but VCDS saved them in one file, I don't know why) which depict cold start, a short ride in a traffic jam and hot ride in a traffic jam mostly stationary because of the clogged traffic.
I have removed MAFs from the list (because they seem to be perfectly fine) and added coolant temperature and throttle position.
My observation is that the engine behaved quite well before it achieved the fully working temperatures. Afterwards it started to shift revs up to 800 RPM from time to time, with no reason (visible for me) for quite a long periods and returning to normal 640 RPM for a very short moments during the whole test.
00022-LOG-11-01F-022-034-705-73F
I'll perform the same test with ECU Engine 1 in the nearest future.
Last edited:
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
I have been looking at those log recordings and found some interesting readings from throttle valve angle sensor.
While idling at traffic light and engine is giving abnormal 800 rpm, the throttle angle sensor is showing 2.7%, although time-to-time shifting down to 600 rpm the throttle angle sensor is showing 1.6%
Without touching the accelerator pedal.
Can it be relative to the whole investigational issue?
While idling at traffic light and engine is giving abnormal 800 rpm, the throttle angle sensor is showing 2.7%, although time-to-time shifting down to 600 rpm the throttle angle sensor is showing 1.6%
Without touching the accelerator pedal.
Can it be relative to the whole investigational issue?
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
Here are logs for Engine ECU 1
LOG-01-01F-022-034-705-73F
00011-LOG-01-01F-022-034-705-73F
In these readings while idling around 600 rpm Throttle Valve is showing from 0.8 to 1.2 mainly.
Coolant temperature 100C° - 113C° while comparing these data.
Any thoughts?
LOG-01-01F-022-034-705-73F
00011-LOG-01-01F-022-034-705-73F
In these readings while idling around 600 rpm Throttle Valve is showing from 0.8 to 1.2 mainly.
Coolant temperature 100C° - 113C° while comparing these data.
Any thoughts?
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
Yeah, it'd be good if we could somehow exclude ETB to be out of question, because Engine ECU 2 at 600 rpm the throttle angle sensor is showing 1.6% meanwhile Engine ECU 1 is showing 0.8% at the same speed of 600 rpm without touching the accelerator pedal. That's two times less than the other ECU. That should mean something.
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
Yesterday I have made more log recordings.
I noticed a huge difference as the engine works much better. Smother and calmer all the period of the driving time.
The main difference I am observing here is that coolant tem didn't travel further than 102C° (differently from the logs made before showing 105C°-113C° accompanied with fans whirling like crazy) and fans were more quiet.
ECU 2 depicting a good driving with stationary idling for quite a long at the end:
LOG-11-01C-023-034-562-705-73F
ECU 1 driving without stationary idling scene:
LOG-01-01D-022-034-502-705-73F
Additional ECU 1 idling for some more minutes:
LOG-01-01F-034-502-705-73F
all recordings performed yesterday, sharing same conditions within the same trip.
Also, I have added "Engine Speed (Specified)" column to the checklist just in case if it may appear to be important.
I noticed a huge difference as the engine works much better. Smother and calmer all the period of the driving time.
The main difference I am observing here is that coolant tem didn't travel further than 102C° (differently from the logs made before showing 105C°-113C° accompanied with fans whirling like crazy) and fans were more quiet.
ECU 2 depicting a good driving with stationary idling for quite a long at the end:
LOG-11-01C-023-034-562-705-73F
ECU 1 driving without stationary idling scene:
LOG-01-01D-022-034-502-705-73F
Additional ECU 1 idling for some more minutes:
LOG-01-01F-034-502-705-73F
all recordings performed yesterday, sharing same conditions within the same trip.
Also, I have added "Engine Speed (Specified)" column to the checklist just in case if it may appear to be important.
Last edited:
- Joined
- Jul 23, 2019
- Messages
- 54
- Reaction score
- 3
- Location
- Georgia (Eurasia)
- VCDS Serial number
- C?ID=645861
After some more driving, I have become clearly confident, that replacement of the fuel pumps and alternator brought a really tangible results.
Vehicle behaves smoother and no more excessive vibrations are felt any more.
Readings of the O2 sensors and relative measuring blocks look better, as you might have seen.
So, this time I have recorded one more log related to battery and alternator behavior.
From almost cold start for about 20 minutes ride:
LOG-61-01F-035-04F-066
Although, I can see that charging power doesn't meet specified parameters all the time.
What do you think?
Vehicle behaves smoother and no more excessive vibrations are felt any more.
Readings of the O2 sensors and relative measuring blocks look better, as you might have seen.
So, this time I have recorded one more log related to battery and alternator behavior.
From almost cold start for about 20 minutes ride:
LOG-61-01F-035-04F-066
Although, I can see that charging power doesn't meet specified parameters all the time.
What do you think?