Caddy 1.9 TDI 4motion BLS 2010

Hello, hope someone could help me out here i got air in fuel lines, from the filter housing 2 the HPFP and in the return line back 2 the filter housing. no air is coming from the fuel tank 2 the filter housing.
Symptoms: Loss of power, intermittent fuel loss 2 engine.

Car was filled with gasoline and was driven until it would not run anymore.

Parts changed: All 4 injector, HPFP, Fuelpump in the tank.

NO fault codes.

any suggestions?

Hi SK2020,
The obvious question is have you changed the o rings in the fuel lines?
Regards HMC

Hello, thank you for the response. yes i have, changed it for the second time just 2 be sure.
also changed the filterhousing without any effect.

This VW has PD injectors.

Hi, please check whether the supply line was accidentally swapped with the return line on the tank.

Sorry, I just see that you wrote that there is no air from the tank. In that case, I would check whether the socket in the aluminum housing on the tandem pump is tight.
As the pump sucks, air could enter there.

hey, thnx for the response!

checked the socket at the tandem pump. no air leaks there. but what i noticed is that the tandempump is making boubles in the fuel inlet and sending it back 2 the filter WHEN i turn of the engine.
when engine is running, the air is coming from the filter housing and goin 2 the tandempump, and also from the return line from the pump 2 the filter. and when i opened the fueltank filler cap i noticed that it sucked in air. almost like it was vaccum inside the fuel tank.
i also noticed some farting noise coming from the tank.
did a smoke test around the filter housing. it does not look like it is sucking in air from there. same on the socket at the tandempump.


hmmm..

Any suggestions?

Just to be absolutely sure, there is clearly a negative pressure in the tank?