Audi A3 2.0 TDI 2006 - Does not start when fuel less than half a tank

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Tue 6 Aug 2013 11:50
Audi A3 2.0 TDI 2006 - Does not start when fuel less than half a tank - keenu

I purchased an Audi A3 TDI 2006 (BKD engine) around 4 months ago and it developed a fault whereby if the fuel level was below half a tank it would not start. This only happens when the car has been left overnight. It cranks fine but it seems it’s not getting any fuel. It can be started with easy start or when the fuel level is raised again to above half a tank.

I took it to the Audi dealer and they first diagnosed fuel contamination (oil leaking in fuel perhaps?). Tank was emptied, new fuel filter and fuel lines cleared. Got the car back and same thing happened.

Again I took it to the dealer and they then replaced the in tank fuel pump. Again the same problem occurred with the same symptoms. There are no fault codes or anything and I believe the dealer hasn’t got a clue what’s wrong.

Any ideas what it could be? I think it’s definitely a fuel issue but what to try next? Could it be a tandem pump issue? I have read these are prone to failures. I have already spent over £900 on this and still no fix so I want to make sure the next thing I do does fix the issue.

Thanks for your help.

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Tue 6 Aug 2013 11:59
Audi A3 2.0 TDI 2006 - Does not start when fuel less than half a tank - dodo

A colleague at work had this problem with her 05 Passat. Alas it was the faulty fuel pump and a well known VAG problem

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Tue 6 Aug 2013 12:10
Audi A3 2.0 TDI 2006 - Does not start when fuel less than half a tank - keenu

Thanks, i believe there are two fuel pumps in these cars, one in the tank and a high pressure one - which is the tandem pump i believe? Was it the high pressure fuel pump replaced?

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Fri 25 Oct 2013 15:49
Audi A3 2.0 TDI 2006 - Does not start when fuel less than half a tank - HalK

Hi,

Can I ask did you get to the bottom of this ? I have a similar fault on an Audi A4 and have changed the same parts as you.

Any more knowledge on this would be really helpfull.

Thanks, Hal

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Sun 27 Oct 2013 09:57
Audi A3 2.0 TDI 2006 - Does not start when fuel less than half a tank - The-Mechanic

I should think the tandem pump will be the cause of the oil contamination in the fuel, I've replaced many of these plus the in-tank pump and filters for the same dirty fuel problems but I'm bothered by the non start with half tank fuel level ?

Every car I've repaired always starts (after bleeding the system of course) without problems and there is only 2 gallons of fuel in the tank after it's been drained and flushed. There must be air being drawn into the system when the level is low(ish) which to me, indicates a problem with fuel leaking back and air being induced. There may be a secondary pick up in the tank linked to the main unit and there maybe a split or hole in the link pipe, but it sounds very much like the tandem pump is leaking (hence the oil contamination) and the fuel return outlet in the tank is exposed when the level is low. When the fuel level is higher it effectively "seals" the system and won't allow air to be induced.

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