jesseusmc

Hey guys have a 2001 audi a8 4.2. Let me start with when I first got the car it would run out of gas at 1/2 a tank. Well my fuel pump went bad so I just replaced it. Well I know I had almost a full tank on replacement and the gas gauge is reading right. Well I drove the car lastnight and I ran out of gas at 3/4 of a tank. I had only drove maybe 40 miles. So I know my gauge is working bur why do I keep "running out of gas" when I still have alot of gas in the tank!?

Kneale Brownson

The pump installation wasn't completed properly.

audijim113

Ditto to what kneale said. Not only was pump not installed correctly but installation may have damaged the pump were it is supposed to sit on a post thing. Speaking from experience.

twentysevenlitres

I would agree.
Where the pump assembly meets the in-tank suction pump, it seals with a metal and rubber gasket.
This needs to mate precisely and seal or it will leak - thats where you run out of fuel at half a tank.
The other pipe that I think Audijim was referring to is a sealed (o-ring) pastic pipe on the upper portion of the pump assembly, which needs to seal into a recepticle on the suction pump. I think it forms part of the left hand suction pump (our tank is a saddle tank, below half full, it basicaly splits into two tanks, which is why it has the complicated suction assembly). That pipe not meeting its hole, or not sealing properly may be where you run out of fuel at 3/4 tank.

Have you read the DIY's?
From personal experience, your first go at this fuel pump will be a very steep learning curve.
Some things I learned:

• The pump cork-screws in very easily once you learn how it cork-screws in! Until then you're convinced it was designed by a blind man!
• The suction pump housing in the tank hangs onto the filler tube in the upper centre of the tank via a large hook. If it's unhooked, you'll never get the pump assembly mounted to it. Ever.
• A boroscope is a very useful tool for seeing the tube with the o-ring on it. Its an absolute bugger to use and find what you're looking for, but you'll never be sure any other way!
• The big long mounting bolt needs to be treated gently. DO NOT OVERTIGHTEN IT, or you'll get it stuck in there. You need to feel for when the rubber part of the metal-rubber gasket has bottomed out on the metal and stop tightening it there - it's sealed at that point. Overtightening risks never getting that bolt out again!

Hope you find this useful