S8 Engine sometimes starts sometimes don't
06-23-2015, 08:03 AM
#12
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06-23-2015, 08:06 AM
#13
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Injection time is missing
06-23-2015, 12:52 PM
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06-25-2015, 11:06 AM
#17
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Looks like I have too low amount of fuel
Hi,
Thank you for your data table.
This is a perfect data set to investigate my problem.
Unfortunately I don't have this data set yet but our recall is that we had 0.76ms of injection opening time instead of 1.53ms compared to yours at 800rpm. The air inflow quantity was exactly the same.
This leads to the conclusion that I don't have enough fuel injected when the car don't start.
I need to figure out based on what sensors the ecu calculates injection time.
I read in the service training book that the exhaust manifold and catalytic converter sensors (oxygen sensors, etc..) may play role in calculating the amount of each injector.
Software issues ruled out according to ecu programmers I talked today.
According the dealer the car has false air from the rubber pipe connecting fine oil separator and the engine, but so far no sign of false air on seals or on pipes.
So I'm replacing that oil drainer pipe and the old fine oil separator because that does not shut from oil drainer direction. This way air can flow into the engine. By the way when the dealer replaced that with the new oil separator the car did not start more even with starting fluid either so the put the false one back temporarily.
Right now I took the air intake manifold off and cleaning from carbon buildup, cleaning all injectors with ultra sound cleaning, and I will test them before building them back in.
Also tomorrow I will measure each injector opening time with oscilloscope, for exact values.
Once again with old fine oil separator, the car was sometimes starting sometimes not. If did not started the with spaying starting fluid it just started right away fine. Also the dealer said when they pulled the cooling temperature sensor the car started right away.
Once the car started it was running just perfect till 300km/h. ( no misfire etc...)
Thank you,
Gabor
Thank you for your data table.
This is a perfect data set to investigate my problem.
Unfortunately I don't have this data set yet but our recall is that we had 0.76ms of injection opening time instead of 1.53ms compared to yours at 800rpm. The air inflow quantity was exactly the same.
This leads to the conclusion that I don't have enough fuel injected when the car don't start.
I need to figure out based on what sensors the ecu calculates injection time.
I read in the service training book that the exhaust manifold and catalytic converter sensors (oxygen sensors, etc..) may play role in calculating the amount of each injector.
Software issues ruled out according to ecu programmers I talked today.
According the dealer the car has false air from the rubber pipe connecting fine oil separator and the engine, but so far no sign of false air on seals or on pipes.
So I'm replacing that oil drainer pipe and the old fine oil separator because that does not shut from oil drainer direction. This way air can flow into the engine. By the way when the dealer replaced that with the new oil separator the car did not start more even with starting fluid either so the put the false one back temporarily.
Right now I took the air intake manifold off and cleaning from carbon buildup, cleaning all injectors with ultra sound cleaning, and I will test them before building them back in.
Also tomorrow I will measure each injector opening time with oscilloscope, for exact values.
Once again with old fine oil separator, the car was sometimes starting sometimes not. If did not started the with spaying starting fluid it just started right away fine. Also the dealer said when they pulled the cooling temperature sensor the car started right away.
Once the car started it was running just perfect till 300km/h. ( no misfire etc...)
Thank you,
Gabor
06-25-2015, 01:46 PM
#18
AudiWorld Senior Member
You are welcome, I would appreciate it if you could document the process of carbon cleaning, my S8 has never had it done so any pictures you could provide and tips would be great
BTW if you are using VCDS for measuring blocks, there is no label files for the S8, this stops you using adv measuring values. but I contacted ross tech and they advised that copying and renaming the
07L-910-552-BUJ1.clb
07L-910-552-BUJ2.clb
07L-910-552-BUJ3.clb
to
07L-910-552-BSM1.CLB
07L-910-552-BSM2.CLB
07L-910-552-BSM3.CLB
doing this will give you the ability to get adv meaus values from the engine controller
BTW if you are using VCDS for measuring blocks, there is no label files for the S8, this stops you using adv measuring values. but I contacted ross tech and they advised that copying and renaming the
07L-910-552-BUJ1.clb
07L-910-552-BUJ2.clb
07L-910-552-BUJ3.clb
to
07L-910-552-BSM1.CLB
07L-910-552-BSM2.CLB
07L-910-552-BSM3.CLB
doing this will give you the ability to get adv meaus values from the engine controller
Last edited by haggisuk; 06-25-2015 at 01:50 PM.
06-25-2015, 05:59 PM
#19
AudiWorld Super User
Hi,
Thank you for your data table.
This is a perfect data set to investigate my problem.
Unfortunately I don't have this data set yet but our recall is that we had 0.76ms of injection opening time instead of 1.53ms compared to yours at 800rpm. The air inflow quantity was exactly the same.
This leads to the conclusion that I don't have enough fuel injected when the car don't start.
I need to figure out based on what sensors the ecu calculates injection time.
I read in the service training book that the exhaust manifold and catalytic converter sensors (oxygen sensors, etc..) may play role in calculating the amount of each injector.
Software issues ruled out according to ecu programmers I talked today.
According the dealer the car has false air from the rubber pipe connecting fine oil separator and the engine, but so far no sign of false air on seals or on pipes.
So I'm replacing that oil drainer pipe and the old fine oil separator because that does not shut from oil drainer direction. This way air can flow into the engine. By the way when the dealer replaced that with the new oil separator the car did not start more even with starting fluid either so the put the false one back temporarily.
Right now I took the air intake manifold off and cleaning from carbon buildup, cleaning all injectors with ultra sound cleaning, and I will test them before building them back in.
Also tomorrow I will measure each injector opening time with oscilloscope, for exact values.
Once again with old fine oil separator, the car was sometimes starting sometimes not. If did not started the with spaying starting fluid it just started right away fine. Also the dealer said when they pulled the cooling temperature sensor the car started right away.
Once the car started it was running just perfect till 300km/h. ( no misfire etc...)
Thank you,
Gabor
Thank you for your data table.
This is a perfect data set to investigate my problem.
Unfortunately I don't have this data set yet but our recall is that we had 0.76ms of injection opening time instead of 1.53ms compared to yours at 800rpm. The air inflow quantity was exactly the same.
This leads to the conclusion that I don't have enough fuel injected when the car don't start.
I need to figure out based on what sensors the ecu calculates injection time.
I read in the service training book that the exhaust manifold and catalytic converter sensors (oxygen sensors, etc..) may play role in calculating the amount of each injector.
Software issues ruled out according to ecu programmers I talked today.
According the dealer the car has false air from the rubber pipe connecting fine oil separator and the engine, but so far no sign of false air on seals or on pipes.
So I'm replacing that oil drainer pipe and the old fine oil separator because that does not shut from oil drainer direction. This way air can flow into the engine. By the way when the dealer replaced that with the new oil separator the car did not start more even with starting fluid either so the put the false one back temporarily.
Right now I took the air intake manifold off and cleaning from carbon buildup, cleaning all injectors with ultra sound cleaning, and I will test them before building them back in.
Also tomorrow I will measure each injector opening time with oscilloscope, for exact values.
Once again with old fine oil separator, the car was sometimes starting sometimes not. If did not started the with spaying starting fluid it just started right away fine. Also the dealer said when they pulled the cooling temperature sensor the car started right away.
Once the car started it was running just perfect till 300km/h. ( no misfire etc...)
Thank you,
Gabor
Is the starting issue:
A. Always (or never) when engine is cold?
B. Always (or never) when engine is warmed up?
C. Sometimes when cold, sometimes when warmed up?
I ask because of the comment in your recent response about the oxygen sensors. In the opening seconds when the car is cold those won't be functioning yet since they are not at operating temperature. The car is basically running on its own default settings at that point--called "open loop" if you read background materials. Thus if it doesn't start when (cold) at times but does start consistently hot, then there is a basic issue with something that the closed loop operation (driven by O2 sensors and MAF's especially) can overcome, but when cold they aren't yet kicking in to help. And likewise if the opposite (starts consistently cold but not hot), it logically is the other direction where one of the closed loop operations is choking it off; unplugging MAF's when it would be in closed loop is a classic way to send it back to open loop as a test.
All this puts aside it could be purely mechanical--like the dealer diagnosis of a bad manifold where there is a crack or something that opens or closes with temperature changes, or a pump or pressure valve or something that is getting affected by temperature or is just having intermittent failures. If you are cleaning the valves, I expect you have the manifold off the car and can inspect it carefully.
Also, for what the dealer said, it sounds like he meant the intake manifold specifically, correct? As in, not the throttle bodies that are bolted directly to the manifold that of course have to move correctly based on the electrical signal they receive.
Last edited by MP4.2+6.0; 06-25-2015 at 06:04 PM.
07-01-2015, 04:31 AM
#20
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Hi,
Answer is C. Temperature does not affect starting failure.
I have cleaned the carbon buildup based on this video:
https://youtu.be/Ugh9vPz2Zd8
Finally and hopefully breakthrough came yesterday investigating and finding the problem.
We have checked each (10) injector signals with an oscilloscope.
First 3 was fine 55 to 65 Voltage with around 12 ms opening time.
However from 4 to 7 the voltage dropped to 27 to 33 Voltage. 8 to 10 fine again. Than we remetered all of them again and all 10 was fine again.
Luckily we have experienced the problem in both valve rows and also on injector which was brand new which indicates that it's neighter the voltage regulator in the ecu since same part not gonna go bad in both nor the injector.
This reading Fitts the problem which is why the audi s8 v10 sometimes starts when enough voltage can be read at the injector, sometimes not when there is not enough voltage so than enough fuel can not be injected and therfore it starts when I spray starter fluid.
Now I have to find what causes low voltage at these high pressure fuel injector.
Our logical best bet is checking all ground points at the ecus and also all power intakes including relays before the ecus providing power, maybe running through 5-6 amps with 12 V in both ground and intake to ecu.
Finding the cause hopefully won't be as hard as finding the problem itself.
Thank you,
Gabor
Answer is C. Temperature does not affect starting failure.
I have cleaned the carbon buildup based on this video:
https://youtu.be/Ugh9vPz2Zd8
Finally and hopefully breakthrough came yesterday investigating and finding the problem.
We have checked each (10) injector signals with an oscilloscope.
First 3 was fine 55 to 65 Voltage with around 12 ms opening time.
However from 4 to 7 the voltage dropped to 27 to 33 Voltage. 8 to 10 fine again. Than we remetered all of them again and all 10 was fine again.
Luckily we have experienced the problem in both valve rows and also on injector which was brand new which indicates that it's neighter the voltage regulator in the ecu since same part not gonna go bad in both nor the injector.
This reading Fitts the problem which is why the audi s8 v10 sometimes starts when enough voltage can be read at the injector, sometimes not when there is not enough voltage so than enough fuel can not be injected and therfore it starts when I spray starter fluid.
Now I have to find what causes low voltage at these high pressure fuel injector.
Our logical best bet is checking all ground points at the ecus and also all power intakes including relays before the ecus providing power, maybe running through 5-6 amps with 12 V in both ground and intake to ecu.
Finding the cause hopefully won't be as hard as finding the problem itself.
Thank you,
Gabor
Important question:
Is the starting issue:
A. Always (or never) when engine is cold?
B. Always (or never) when engine is warmed up?
C. Sometimes when cold, sometimes when warmed up?
I ask because of the comment in your recent response about the oxygen sensors. In the opening seconds when the car is cold those won't be functioning yet since they are not at operating temperature. The car is basically running on its own default settings at that point--called "open loop" if you read background materials. Thus if it doesn't start when (cold) at times but does start consistently hot, then there is a basic issue with something that the closed loop operation (driven by O2 sensors and MAF's especially) can overcome, but when cold they aren't yet kicking in to help. And likewise if the opposite (starts consistently cold but not hot), it logically is the other direction where one of the closed loop operations is choking it off; unplugging MAF's when it would be in closed loop is a classic way to send it back to open loop as a test.
All this puts aside it could be purely mechanical--like the dealer diagnosis of a bad manifold where there is a crack or something that opens or closes with temperature changes, or a pump or pressure valve or something that is getting affected by temperature or is just having intermittent failures. If you are cleaning the valves, I expect you have the manifold off the car and can inspect it carefully.
Also, for what the dealer said, it sounds like he meant the intake manifold specifically, correct? As in, not the throttle bodies that are bolted directly to the manifold that of course have to move correctly based on the electrical signal they receive.
Is the starting issue:
A. Always (or never) when engine is cold?
B. Always (or never) when engine is warmed up?
C. Sometimes when cold, sometimes when warmed up?
I ask because of the comment in your recent response about the oxygen sensors. In the opening seconds when the car is cold those won't be functioning yet since they are not at operating temperature. The car is basically running on its own default settings at that point--called "open loop" if you read background materials. Thus if it doesn't start when (cold) at times but does start consistently hot, then there is a basic issue with something that the closed loop operation (driven by O2 sensors and MAF's especially) can overcome, but when cold they aren't yet kicking in to help. And likewise if the opposite (starts consistently cold but not hot), it logically is the other direction where one of the closed loop operations is choking it off; unplugging MAF's when it would be in closed loop is a classic way to send it back to open loop as a test.
All this puts aside it could be purely mechanical--like the dealer diagnosis of a bad manifold where there is a crack or something that opens or closes with temperature changes, or a pump or pressure valve or something that is getting affected by temperature or is just having intermittent failures. If you are cleaning the valves, I expect you have the manifold off the car and can inspect it carefully.
Also, for what the dealer said, it sounds like he meant the intake manifold specifically, correct? As in, not the throttle bodies that are bolted directly to the manifold that of course have to move correctly based on the electrical signal they receive.
Important question:
Is the starting issue:
A. Always (or never) when engine is cold?
B. Always (or never) when engine is warmed up?
C. Sometimes when cold, sometimes when warmed up?
I ask because of the comment in your recent response about the oxygen sensors. In the opening seconds when the car is cold those won't be functioning yet since they are not at operating temperature. The car is basically running on its own default settings at that point--called "open loop" if you read background materials. Thus if it doesn't start when (cold) at times but does start consistently hot, then there is a basic issue with something that the closed loop operation (driven by O2 sensors and MAF's especially) can overcome, but when cold they aren't yet kicking in to help. And likewise if the opposite (starts consistently cold but not hot), it logically is the other direction where one of the closed loop operations is choking it off; unplugging MAF's when it would be in closed loop is a classic way to send it back to open loop as a test.
All this puts aside it could be purely mechanical--like the dealer diagnosis of a bad manifold where there is a crack or something that opens or closes with temperature changes, or a pump or pressure valve or something that is getting affected by temperature or is just having intermittent failures. If you are cleaning the valves, I expect you have the manifold off the car and can inspect it carefully.
Also, for what the dealer said, it sounds like he meant the intake manifold specifically, correct? As in, not the throttle bodies that are bolted directly to the manifold that of course have to move correctly based on the electrical signal they receive.
Is the starting issue:
A. Always (or never) when engine is cold?
B. Always (or never) when engine is warmed up?
C. Sometimes when cold, sometimes when warmed up?
I ask because of the comment in your recent response about the oxygen sensors. In the opening seconds when the car is cold those won't be functioning yet since they are not at operating temperature. The car is basically running on its own default settings at that point--called "open loop" if you read background materials. Thus if it doesn't start when (cold) at times but does start consistently hot, then there is a basic issue with something that the closed loop operation (driven by O2 sensors and MAF's especially) can overcome, but when cold they aren't yet kicking in to help. And likewise if the opposite (starts consistently cold but not hot), it logically is the other direction where one of the closed loop operations is choking it off; unplugging MAF's when it would be in closed loop is a classic way to send it back to open loop as a test.
All this puts aside it could be purely mechanical--like the dealer diagnosis of a bad manifold where there is a crack or something that opens or closes with temperature changes, or a pump or pressure valve or something that is getting affected by temperature or is just having intermittent failures. If you are cleaning the valves, I expect you have the manifold off the car and can inspect it carefully.
Also, for what the dealer said, it sounds like he meant the intake manifold specifically, correct? As in, not the throttle bodies that are bolted directly to the manifold that of course have to move correctly based on the electrical signal they receive.