Ryan Phillip Phinny

Good evening,

I'm in a bit of a boggle so here's the background. 2002 A8, 254k on the body with 15k on rebuilt drivetrain/engine.

I have to get my vehicle to pass emissions and I noticed the catalytic converters were sporadically getting weak. I decided on a fuel system treatment to simply see if I could clean it up. The worst that happens is the fueling system is cleaned.

I run it through the cleaning cycle and I notice the exhaust got slightly louder and it ran a little bit rougher but attributed that to the change in fuel with the cleaning agent. Got all the way through that and refilled with Shell premium as always and upon restart, she bogged a bit and died. I thought that was weird and started her a second time and she started right up. Got her home and no issues. Couple days go by and I'm headed home from work with no problems. I pull into the driveway and idle for maybe 20 seconds when she just dies. I can't get her restarted this time.

I start searching on here but there was just so many things it could be I started with just changing the fuel filter and seeing what happens. No problems there however I go to start her up again and no fuel is coming out. Ok, so I test the pump with a hot wire from the battery and sure enough, the pump died. I ordered a new one and installed it. Got plenty of fuel now as indicated by the slight drip out of the fuel filter which I tighten down and then proceed to start her up. Well, no joy. So I pull the FPR thinking that it might be that and when I pull, inspect and reinstall, it stumbles to life for a second then dies. I think I have it now and get a new FPR. Well, funny story it doesn't fix it and the spark plugs are now fouled to **** with fuel and soni change those preemptively.

Any ideas on what's causing this major annoyance?

thanks!

Ryan

jfrahm

Add fuel to the tank to prime the pump. Also make sure you put in the correct A8 pump, the wrong one fits but you run out of gas early as the common pumps do not have the facility to scavenge fuel out of the deep sections.
If you do have the correct pump it is possible to install it such that it does not drive the scavenge pumps.

-Joel.

hillpc

1997 A8Q. I had a similar problem a few weeks ago, in which the car would run fine for a few (less than 5) seconds and then die, after every start. It sounded like it was running out of fuel.

Air inlet to the throttle body from the air cleaner was partially off. (I hadn't finished putting it on after some work under the hood.) Hooked it up and it runs fine. Seems that maybe it actually was running out of fuel, since the air mass flow sensor was only seeing that part of the air coming through the air cleaner. Cut back fuel to match that amount, which wasn't enough to keep the car running. That's my theory on that.

Joel makes a good point about the fuel pump possibly being installed incorrectly (or the wrong one). I understand that if this happens the car will run out of fuel somewhere around 1/3 tank level. Do you have enough, or can you get enough fuel into the tank to know it has enough in it for this not to be an issue?

Ryan Phillip Phinny

I'm sitting at 3/4 a tank so I don't think the fuel pump is an issue, not to mention a fuel smell comes after a really healthy crank (>5 seconds). I checked the air inlet and its tight as well. I'm leaning towards a crank position sensor at the moment, because it seems like no spark is happening.

any other suggestions would be awesome. Thanks!

hillpc

My crank position sensor wires melted against the exhaust because I hadn't put them back in a protected spot when I rebuilt the trans. Took a couple of months to start having problems. Stranded me once, but started right up before the tow truck got there. I still had the truck take it and me home because I didn't know what it was yet. Then died while I was checking trans fluid level, gushing fluid all out the fill port. It was obvious what the problem was when I started poking around and looking with a flashlight, after diagnosing no spark signals coming into or out of the 2 ignition modules with an LED tester.

audinutt

If the crank position sensor were bad you wouldn't get injector pulse. He said that he smells fuel. So I think it's highly unlikely it's the CPS.
It still could be a fuelpump issue, try disconnecting the MAF sensor and see if you have any change.


-RIchard

Ryan Phillip Phinny

UPDATE!

I hate hanging threads, so I came back after the fact.

Turns out, the pump I ordered was defective. It wasn't a VDO.. so that could have had a part to play. The second pick up wasn't there which the VDO had. In addition, it was producing ~20lbs of pressure at start up which was BARELY enough to get gasoline to pulse through the injector, get the plugs soaked, but that's about it. I replaced it with a VDO pump and voila, no issues. Hopefully this helps someone else in the future.

~Ryan