Mike_k

Go figure, California is about to have it's one monsoon in 5 years and the A8 craps out on me tonight.

Anyhow, I'm driving home and I go to give it some gas and it chokes. This is a familiar feeling. My 2004 had a fuel pump failure of the primary pump so it would run for 30 seconds and then die once the secondary pump shut off.

So this basically won't get over 3000 rpm. It starts chugging really bad at that point. Idle is choppy and I can hear something around the manifold, I suspect it's the sound of gasoline intermittently entering the fuel rails. It sounds like it's coming from the high pressure lines.

So not having had an FSI car before I'm going to defer to those with more experience. Does this sound like a fuel pump? I assume the fuel pump setup for the FSI cars is different than that of the older cars due to the pressure differences, yes?

Any way to easily verify it's the pump?

MP4.2+6.0

Haven't had the failures, but I would give it a Techron dose pronto anyway.

Mike_k

I doubt that's going to do much for me... This sounded like a failing component. Lots of noise by the high pressure rails up front.

Now I'm just not sure. The car has been problem free and this problem happened immediately after a 2-1 manual downshift that I hit a bit too early when slowing and brought engine revs up quickly. After the car was off for about 30 minutes I started it back up and let it run for 10 minutes, hoping to hear that noise again. No dice... So I took it out onto Mulholland (crazy road that runs along the top of the Hollywood Hills) and beat the snot out of it for a good 10 minutes. Not a hiccup.

I suppose I'll keep an eye on it and report back. I wonder if that sudden jump in rpm introduced some air in the system that wasn't purged until pressure was bled off and it was primed again.

dvs_dave

Look for fuel pressure warnings in VCDS.

I've a Mini Cooper S with DI and they're notorious for failing high pressure fuel pumps. Twice now in 5000 miles for me. Telltale is hard start when cold, intermittent struggling with higher revs and a rough idle. Diagnostics bring up low pressure in the high pressure fuel line. Audi has a similar setup.

Mike_k

I drove it about 3 hours this morning without a hiccup. I'm really thinking I did something with that 2-1 kickdown that set the fuel system off. A sudden rise or drop in pressure perhaps started a diaphragm in the pressure regulator fluttering and didn't stop until flow stopped or perhaps air entered the system. Obviously speculation on my part but there was a very specific event that started the problem and it hasn't occurred since. It doesn't follow the tell-tale signs of a low pressure fuel pump failure and I can't seem to find anything to suggest that the high pressure pumps fail with any kind of regularity unlike my BMW 535.

dvs_dave

Mini Cooper S has the same junk high pressure fuel pump as the 535.

Have you tried the 1-2 kickdown again?

Mike_k

Just a follow up on this. The problem never reoccurred.