Audi Logic

here's the problem
the car stalls.. I figured it was the fuel pump but now I'm not sure.. I took the pump out of the car connected it to 12V and had it pumping water for a while with no problems..
put it back in put 20 bucks worth of gas in the tank and drove for like an hour and it ran good..
about 15 min later it stalls again..
last night I pulled the pump again and used it to empty the tank, worked great pumped and pumped till the tank was empty (about 10 gallons)non stop..
why would it run fine outside the car and when used to empty the tank but stals when driving?

4Driver4

This is an Audi. If you have a pump that you even suspect is bad, replace it. It one of the few parts know to leave you dead on the road if/when it fails.

There are several factors to be considered. First, the longer it runs and the less fuel in the tank, the hotter it gets. I've seen cars that would die with less than a quarter of a tank of fuel but run OK otherwise. Second, the load on the pump and the pressure it needs to maintain are both higher when it is running the car than when it is pumping out the tank.

Audi Logic

hate to have to go back and by another part to fix the same problem...

4Driver4

caution, rather than rushing to replace anything and everything in the attempt to fix a problem.

brians97A6Q

classically noisy pump, and when I replaced my fuel filter, the noise went away. I figured that the old filter was so clogged that is was increasing the head pressure on the pump almost to the point of failure, while the reduced pressure through the new filter allowed the pump to work easily.