Air bubbles in fuel line coming from fuel filter?

HiRoller

Member
Joined
Jan 11, 2012
Location
Cambridge, UK
TDI
Seat Leon TDi 110 (ASV)
I have tried to rid my system of airbubbles and I'm struggling..

So far I have:

  • Removed fuel pick-up return check valve (as per the 'Andy Pandy' mod)
  • Installed OEM type fuel filter without Tee valve - The IP returns direct to tank.
  • Silicon Leak Off Hoses.
I am running B100 but when running on dino the issue is the same.

Things Im going to try:

  • Jubilee/Mikalor type clamps on the fuel filter.
  • I actually suspect the black plastic hose that has a barbed connection to the clear section.
Beyond this I think I'm condemned to bad IP seals.
 

DieselDenny

Well-known member
Joined
Jan 30, 2009
Location
Dauphin, PA
TDI
96 Passat
I just went through a similar issue with my 96 Passat (B4). At first it was just taking longer to start....it would crank for about 7-10 seconds before firing over regardless of the temperature. Then it would stall out while driving. It would start back up but with some difficulty. There was also pretty many "soda bubbles" in the clear fuel line going to the injectors. After reading this thread and some other threads on the subject, I pulled the sending unit and it was a different one than this one pictured above but it looked very clean and seemed to be functional....no blockage and nothing to drill out. So I figured I would try the fuel filter....it was due to be changed anyway. Out of curiosity, after I pulled the filter I poured the contents into a small container. To my surprise, a bunch of black chunks came pouring out....it looked just like what was pictured above so I assume it was algae. I don't know how it formed in there but I put the new filter on, fired it up and it ran stronger than it has in some time. When I started it up again it fired right up with no hesitation and there are now virtually no air bubbles in the fuel line. Problem solved. My question is; do they make a fuel additive that contains an algaecide or is that even something you would want? HMMM? Anyway, I hope this helps someone who might be having this similar problem.
 

efv789

New member
Joined
Jul 31, 2011
Location
Carrollton, IL
TDI
2002 Jetta 5-speed swap
I fought with all of this and also never found a solution. It's best to do all the things listed previously first, but my only solution after trying all that was:
 
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