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#1
20th April 2016, 10:12 PM
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Audi A8L 4.2 doesn't start. Air bubbles in fuel
Hi
One day I started my car, but after few minutes its start dying, revs was slowly droping down and acceleration pedal didn't respond. After car stalled and didn't start any more. Car already over one month in garage and they can't found what wrong. Just what they told me, that fuel coming from tank to engine with air bubbles. Fuel pump is working. Maybe someone had same issue or knows where to check? Because its looks like they will never fix it. Thanks for any help Igor
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 A8 Rules 
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#2
21st April 2016, 06:33 AM
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Not sure. But thinking about it logically if there is air in the system it can only be coming in from the tank / pump as after that point it is under pressure and would leak out. Have you ever had a fuel pump?
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1996 A8 4.2 QS. Bose, Solar roof, um...um... rally sport towbar. Now gone to a new home as the Traders 8. Bright yellow bus o love.
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#3
21st April 2016, 07:59 AM
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The common fuel tank/pump issue perhaps (behaves like it's run out of fuel at around 1/4 tank-full)?
Does it run if you fill it up to half a tank or more?
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Mark ------------------------------------------------------ 2002 FE S8 Ebony Black Pearl ------------------------------------------------------  ------------------------------------------------------ Cars Owned: The Tesla Era: 2020 Model S Performance Ludicrous+ (present) (Black, with all black premium interior and carbon fibre décor, 21" sonic carbon twin turbine wheels and FSD capability) The Audi Era: '97 A8 4.2 (Ming Blue) --> '96 A8 4.2 QS (Dark Green) --> '02 FE S8 (present) The Citroen Era: '84 BX 1.6 RS --> '89 BX 1.9 DTR Turbo --> '94 XM 2.0L Turbo --> '96 XM 2.0L Turbo Exclusive --> '00 Xantia Activa 2.0L Turbo The Banger Era: '76 1.2L Lada VAZ-2101 (Ruski Fiat 124) --> '80 1.7L Morris Ital HL, finished in Ermine White and Rust
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#4
21st April 2016, 08:57 AM
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Garage said that pump is ok. And they checked fuel lines under car. They try to put more petrol as well, nothing.
I remember, before its happend, I tried to start car with blank key (my mistake  ), if its help. But after I swap key to main one and car started. So next day after I start car, problem appeared.
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A8 Rules
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#5
21st April 2016, 10:02 AM
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Does it fire up and then stall? If it does is the IMO light flashing on the dash?
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1996 A8 4.2 QS. Bose, Solar roof, um...um... rally sport towbar. Now gone to a new home as the Traders 8. Bright yellow bus o love.
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#6
21st April 2016, 11:12 AM
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I am not sure if it is the bubbles in fuel causing stalling but if it is then like Dezzy said they can only enter the stream before pump. So the issue could be pump incorrectly seated or seals failed. You say they filled in more fuel- how much? Try at least 1/2 tank. After that turn ignition on and off several times couple of seconds at the time to allow pump to circulate the fuel and get rid of air. You should be able to hear bubbles going through system and reduce with time as you cycle ignition.
If it's not because of the bubbles then then it could be immobilizer again like Dezzy said. Does the IMMO light come on with ignition and then go off? There would also be fault code stored in ECU and immobilizer. Other things could be MAF, throttle body with associated wiring or vacuum leak.
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Currently 8less 2011 Q7 S Line 3.0TDI, 2016 Tesla Model S 90D 8 history: 2006 A8 Sport 4.2TDI quattro SOLD, 1997 S8, reached end of life with gearbox failure
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