Audi Repair: Audi A8 wont start after fill up, fuel filler cap, audi a8

Question
QUESTION: Hello,
 Thanks for taking the time to read this because I'm getting sick trying to find gas stations with no one in them.  Anyways, every time I put gas (premium grade) in my 2000 Audi A8  I have alot problems starting my car. I usualy have to hold the ignition down and pump the pedal. Once the car starts it idles funny - does a little shimmy shake , then i'm off on my way like nothing happened.  Everytime i start the car after that it starts with no problem.  Only when I fuel up..  I ran the obd2 and I came up with a Vac leak.. but not sure if thats the problem-- and if it is where do I start.?  Any ideas I would love to hear them..
Thanks again
Frank

ANSWER: When you remove the fuel filler cap is there a hissing sound?  I cannot think of a reason why there should be a difference with a refuel-start or any other.  I would try this, do a fuel stop and time yourself.  Then repeat the experiment without the fuel filling part, wait exactly the same amount of time and re-start the car.  Is the behavior the same?  Let me know,  Jan

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QUESTION: Taking the gas cap on and off has no effect.  Only when I re-fuel. I trying buying a new gas cap and had no such luck.. I've even tried clearing all codes , filling up and had same problem. Any other Ideas? I appreciate them all.
FRank

ANSWER: This is very weird.  I will be seeing a friend of mine tomorrow who knows Audi's and their quirks too; he might have an idea.  Did you verify it was not just a timing thing?  Is there a chance something in the gas tank is moving around?  Cheers,  Jan

---------- FOLLOW-UP ----------

QUESTION: I just did the major tune replacing the timing belt, water pump , thermostat , etc.  It did the same thing before and after. My father in law is a mechanic who has been doing the work and even he is scratching his head. He just did the steering rack on it Sat., a common problem with the seals. I'll run it through the scanner and get you the exact codes, maybe this will help solve the mystery.  If you watched me start the car after filling up , you would probaly crack up.

Answer
Did you try my suggestion about checking the time that the engine is off for a re-fuel, and one without?  I spoke to another expert today who also could not offer any suggestions...  Let me know all the codes, and we'll have a fresh look at it.  Cheers,  Jan