Gasoline pump

Must open a new Thraed, since the problems are probably bigger.
Today I removed the pump housing according to Rep Guide, resealed, installed a new pump and reinstalled everything after assembly according to Rep Faden. Then five liters of gas on it and go to the test drive. ==References== He's gone out 2-3 km. New canister on it and back-again. I wanted to put it back in and out, but something came to my mind. Now my friend "in the meantime already" has the previously pumped about. 70 l re-filled and a test drive made because he did not want to believe the pressure-test procedure of Audi. Strangely enough, he went out again after 4 km and after 5 l fill in again back and again out...
Should the car not be running with almost full tank despite obviously not properly installed pump housing? I assumed that the case was to blame, that it was 1/3, or. 1/4 full tank stopped and the car the day before yesterday then completely striked (thought the pump might have pulled air and is completely over-the-counter also the new one). Anyone ever had a similar problem or a tip what it might be? Maybe a hose close to the housing?
Thank you so much... I'm desperate...