TDI Diesel Air Intake Hose for Audi

Hello everyone.
'I'm experiencing a problem where, when my car is parked on a slight incline (facing backwards), all the diesel fuel flows back from the supply line into the tank. At least, that's what it appears to be, because there's no more diesel visible in the transparent supply line leading to the pump. Consequently, the engine won't start. However, when the car is parked straight or on the same spot but slightly tilted forward, there are absolutely no problems.'

Regarding the car.

Audi A4 2.5L TDI.

Engine AKN.

Manufactured in 2000.


I hope someone can help me, or has encountered this problem before.

'I think it's a good idea to thoroughly check the entire fuel system for leaks. It definitely smells like it's drawing in air. You don't necessarily have to see diesel leaking from the points where there are leaks. Sometimes, even a slightly loose or misaligned clamp can cause air to enter the system. Another common issue is improperly installed diesel filters or porous fuel lines. Based on my own experience, I wish you good luck with your search. Here's a tip from someone who's been through it: systematically replace all the hose clamps. With a bit of luck and careful tightening and clamp selection, you might solve your problem.'

Thank you, Jörgs, for your tip.

I already tried that, but unfortunately I haven't been able to find a solution.
Could it be that a check valve is defective? If so, where could it be located? (I hope it's not inside the diesel pump [VP44], because that would certainly be expensive.)

Hello,

How about using a suitable hose to connect directly to the source and then sucking it up with your mouth and an additional 1-meter hose?
You would quickly get a sense of where the air is being drawn in.
Please only suck with your cheeks; taking deep breaths through a diesel engine might be more disgusting than the worst possible mouthwash.

Best regards, Rainer.

What exactly did you do?

'When I bought my future winter A4 in March, it still had cold start problems. However, I didn't pay much attention to it because the battery wasn't great and there were other issues with the car that needed addressing. Once I finished all the other work on the car, I planned to deal with it then. The diesel filter was only about 5,000 km old and had been replaced by a professional workshop, as documented. The fuel system was completely dry... I couldn't see anything obviously wrong. When I converted it to run on heating oil, I noticed that the O-ring on the DFI (direct fuel injection) unit was missing, and two hose clamps weren't properly tightened, allowing air to enter. I then replaced all the hose clamps with stainless steel clamps, and since then, everything has been fine.'

Something different:

Does an AKN draw air?

That makes me think that the VP44 should NEVER run dry!?!?

Does this also apply to a run where the fuel tank is completely empty, or only to situations where the tank is intentionally drained?

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

The ESP system should not be able to fail completely because the control unit will shut down in several stages beforehand (e.g., due to a low fuel level in the tank, intermittent low fuel levels, or an empty fuel tank).
Small air bubbles aren't usually a big problem. In my case, even under full load, I get error code 550, which indicates an issue with the injection timing, because there's always a large air bubble (and many small ones) coming from somewhere when the engine is warm.
I think I need to find out where this is coming from. Thanks to Volkswagen and Audi, there's always something to do.
Are these cars even still available for purchase? Something else is constantly breaking down...