barackuda

Hello all.New to the forum and Audi ownership.Bought a 2000 S8 manual 6spd with 270k km on the clock.I drove it from Slovakia all the way to Scotland (2500km) and 3 weeks driving in here. This is what happened.Last two days when headding to work at 6pm it started ok.After nightshiftat 7am starting was but difficult but it did.Suddenly on Friday night 4am didnt started at all.Engine was cranking but no catch.
Next day I pulled the crank position sensor cause I read a lot that it might cause the problems. Measured accross pins 2 and 3 about 880 Ohm (ELSAWIN says this is corrrect).Then pins 1 and 2 and 1 and 3. No shortcut there.Dont know if you switch the multimeter to buzzer if it should make a noise or not. Put the sensor back in and nothing.Didnt start.
Pulled the fuel pump relay and gave it a clean (dont know how to check if its ok).
Then I disconnected the fuel line at the pump and put in a small hose with hollander sealing on it to see if the pump is putting out some fuel.Frien of mine cranked the engine but no fuel.I hold my finger on it and no pressure.Then I put a blue roll paper on the outlet of the pump and cranked the engine.The paper was soacked with petrol.

I am puzzled what could be the problem.

Any help greatly appreciated.

Danny

JoePGT5S

Wow, an S8 with manual transmission from the factory. You are the envy of S8 owners the world over. Let me know if you'd like to sell it - I'd love to import it to the USA for the transmission :-)

Fuel pump failures are common on these cars, so you could be on the right track with your diagnosis. See if the symptoms change with a full tank of fuel.

barackuda

Hi Joe..
I have like half a tank of fuel.I don't think its the case of empty tank.Just filled her up 4 days ago.
I'll check the pump relay tomorrow in work.Will connect it to a 12V battery and test it if its engaging or not.

Yeah, 6 spd is amazing on this car. 01E transmission also very strong. She drives great, quick and agile at speeds. Might need a new clutch, as it was slipping at hard launch...

Also has the NAVI plus radio, onyl two in this trim available for sale in europe. Bought he for 4.7k euros...

Danny

JoePGT5S

Sounds like a really nice car!! Would love to see some pictures of it if you have any.

I grew up in Scotland by the way. Which part did you visit?

nossisnave

Hey barackuda
Yeah that does sound like an amazing beast you have!

I think what Joe was referring to is a problem some 8's can develop when the motor will crank but not start and it seems to happen when the gas gets down to half a tank. Mine would do this as well. Due to the design of the fuel tank being molded around the drive shaft, Audi uses a system of hoses going over this hump to pickup gas but apparently this issue can be caused by a poorly fitted O-ring in the nipple of the piece that connects to those hoses and many folks say it happens whenever the tank is half full.

Strange as it may sound my car will still do this somewhat regularly, and the way l get around it is to tap the gas pedal a few times while cranking. Maybe your problem is different but it could be worth a shot. If l don't tap on the gas it will crank until the battery is dead.

I should say mine does this regardless of how much gas is in it so your issue may be different but you never know till you try. Hope this helps

barackuda

Just to be sure, I will test the with directly connecting it to 24V supply and see if it works.
I'll leave it in the tank, disconnect the fuel line and connect my homemade pressure rig just a 100psi gauge with some hose on it.

Should show some pressure if it works...
Or?
Not sure if its drawing air, if it will show some pressure, also not sure if the pump is audible when mounted in the tank.

Any help?

Danny

twentysevenlitres

Not quite right, but close! The fuel pump assembly mates to a housing in the tank where all the suction hoses connect. Where the assembly mates, there is a rubber/metal gasket which seals a bowl that the fuel pump proper sits in. If this does not seal, once the fuel tank falls below approximately half a tank the pump will start sucking air. There is also a feed tube which seals with an o-ring on the assembly, which is probably the o-ring to which you refer. There's lots of angst over getting this feed tube into its recepticle. If the pump housing mates properly, this tube and o-ring will be mated properly as well.

The check for this is to pour a couple of litres of fuel down the filler nozzle. The desig if the filler neck is such that the fuel will pour into the fuel pump bowl first. If the car subsequently starts, but runs dry a few miles later, you've found your problem.

nossisnave

Thanks for clarifying, Twentysevenliters

barackuda

dis just that..poured in 6 litres and nothing.a friend ofcmine was in the boot to listen for some noise from the pump.he could hear a light hum.I could hear it too when we changed places.....
Next I will disconnect the fuel line close to the regulator and see if Im getting fuel there....

any other ideas?

barackuda

I am puzzled.... I disconnected the fuel hose close to the fuel rail (black arrow on picture) to see if I get fuel when I crank it...
And the sucker soacked a rag completely within 3 seconds of cranking
I assume my fuel pump is OK then????

Must be the CRANK POSITION SENSOR then.Nothing else comes to my mind...

Your thoughts on this?

Danny