Good Afternoon all I have a question about the little transparent glass/plastic tube that is part of the diesel filter housing. I've attached a video so you can see.

So my question is, shouldn't this be full of fuel? if yes how do I get it full of fuel? and what is the cause.

Thank you all in advance.

2.2 Tdci 115T280
Year 2010
fwd - LHD

 

Some air can become trapped in the filter , but it eventually will get out and on many vehicles this is considered normal..