ggjoy

The history (I'll try to be short):
- 1999 A8 with 185K
- Car became tough to start a few days ago, then would not start
- To check for fuel, broke the engine bay fuel line - no fuel with ignition on
- Checked fuses - Fuel pump fuse was blown
- Replaced fuel pump fuse - turned ignition on - fuel burst out of fuel line
- Reconnected main fuel line - started and ran for few seconds, then fuse blew
- Ordered just fuel pump (entire assy too expensive) and replaced fuel pump
- What a pita! Did not order gasket set, just tried to reuse existing gaskets - new gasket set for fuel pump about $120!!
- Got it all back together, and started car
- Car ran for a few minutes, then RPMs would gradually drop, till car dies
- Turned ignition on for about 30 seconds then restarted - same result

Questions:
1. I'm confident the fuel pump was drawing too many amps and was bad due to fuses
2. Is the fuel pump/gaskets/system drawing air and not maintaining pressure?
3. Despite all existing gaskets looking ok, is this a gasket problem?
4. I will do a fuel pressure test tomorrow to check for pressure leak down on the fuel rail
5. Other posts mention a Fuel Pressure Regulator - possible?
6. There is no fuel in my oil so pretty sure injectors are not leaking
7. Tried to check for codes but my VAG scanner which works perfectly on other cars, gets nothing but "link error" on my Audi.
8. Lastly, I do not have a Bentley manual - just doing this all off of mechanical experience, Audi posts, and any Youtube videos I can find.
Thanks in advance!

midnightgolfer

I'm a total newb, but I have gotten pretty good at pulling out and replacing my A8 fuel pump.

I think replacing the gaskets and crush washers is worth it, especially the pick-up tube o-ring, and the weird two-sided metal trapezoid thing at the bottom.

However, when I put a new pump in mine, it would do the same thing as yours, run for a few seconds, and then kaput. UNTIL, I filled the tank all the way up. It now will drain all the way down to zero, both sides of tank.

My theory, and I hope someone will correct me if I'm wrong, is that there is some sort of "prime the pump" thing going on here.

I don't know if it is the correct procedure, but in my observation, the fuel pump now drains the left hand side (the side opposite from the pump,) first, and then drains its own side.

In any case, good luck. And I hope someone else has more experience with this, and can help you better.

silverd2

Did you refill the tank completely, to "burp" the pump?

Where did you get the pump? VDO or a cheapie that supposedly is the "same"?

Are you sure you seated both fuel connections on bottom when reinstalling? ...this is the step that many get wrong, no matter how right it felt.

silverd2

We were posting simultaneously...you have a great point. My pump has not gone bad yet, so I have no hands-on with this in particular. But have read volumes of posts and procedures..and the full tank does it for some with problems like this and is recommended by those with much more experience with fuel pump than myself.

Everyone seems to agree that Bentley's instruction to only put in a small amount after installation, to test it, is a load of crap.

ggjoy

Forgot to mention...the fuel filter was changed about 15K ago. Thanks to all your posts, I burped the filter by filling up the tank. The car runs great so far...now let's see what happens when I get at, or below 1/2 tank! lol I did have a borescope that I was able to watch the transfer tube drop into place. Great relief!