Hello, I have again problem woth my skoda, now airbubbles is coming from fuel filter and engine is shaking. And in some time fuel filter will have air pressure inside, so what could be the problem? I think that its the return valve problem what is in top of the fuel filter.

Have you removed the tank sender unit recently?

 

Mistakenly reversing the feed and return lines will give the problem you have.

I just changed fuel filter, bleeded air out of the fuel filter and thats all. And before fuel filter replacement there were also much bubbles coming out of fuelfilter

20 minutes ago, tann said:

And before fuel filter replacement there were also much bubbles coming out of fuelfilter

WHich makes me think you have a leak in the line feeding the fuel filter.

How long have you owned the vehicle and when did the problem manifest itself?

 

What work was done before the problem?

 

Air is being drawn in to the fuel line which is either a leak or a flow restriction, reversed connections to the fuel sender unit will cause the latter and in my case provokee the former on the seals of the fuel filter cartridge.

 

The connections have different colours  but interchangeable, the photo in the Haynes manual was black & white & made it look like the connections should be reversed, they may even have done so themselves before taking the photo, it can take months before an airleak manifests, the pump has to work much harder but does overcome the non return valve just, in doing so it creates a considerable depression across the filter and supply line.

I got all working, back fuel pump had problems, and because of that it drawed out of fuel. Now it works fine, thanks everyone for helping!!