Fylx

Hi, i have 02 A4B6 2.5 tdi engine, yesterday at cold weather, i just can't start the car. It cranks, but no bite, i check fuel line and find out, that fuel pressure before and after fuel filter is very low. After fuel filter it has almost no pressure, got air bubble in line, and cranking doesn't move it. I checked on friend car, on his 2.5 tdi engine, after fuel filter pressure is twice as mine. Fuel filter is new and there is 2 fuel pumps, one in tank, and one for high pressure. Does high pressure pump provide pressure to fuel line form tank, or it's just gas tank pump problem?