Audi Q7 dont start 3.0 tdi

[GERCOMOTIVE]

Hi everyone, I have an audi q7 3.0 tdi year 2005 that won't start.
Do not generate fault codes with the diagnostic machine, and I cannot find the problem.


It seems that it ran out of battery and did not start anymore, I have put a new one and I have coded it. The start turns well but I think the fuel circuit is depleted.


I have seen that it has a Pre-pump in the fuel tank, but it never turns it on when I turn on the ignition, I have tried to bypass the pump relay, the pump works and even if I leave the pump relay bypassed it does not start either.


Do you know if this prepump has to always work? Or is it just supportive and do you use it sometimes?


Thanks in advance

[Milicija]

Hello,

The electric fuel pump in tank should turn on for few seconds when You turn on ignition and then stop. When you crank, or start the car this pump always works - is on. Anyway, check with your diagnostic machine the fuel pressure in the rail, should be atleast +-250 bar.