Air Bubbles In The Fuel Line

smos1

Veteran Member
Joined
Jun 28, 2008
Location
Seattle, WA
TDI
'96 B4V w/AFN swap, 2011 JSW with a leaking pano
96 B4V, has an AFN replacement due to a tensioner causing the TB to fail and lots of interference happened. Lately I've had a noticeable raw fuel smell when getting out of the car after driving it. And sometimes could smell it in the car as well. Looking for the reason I noticed air bubbles in the supply fuel line with the car idling.
Every piece of fuel line and clamps have been replaced from the hard line before the fuel filter to the IP. I've tried different fuel filters, and different "t's" (the thing that fits in the fuel filter). Nothing seemed to make a difference.
There is absolutely no sign of fuel leakage anywhere, I've had someone else with more knowledge than me look with no success.
Would bad IP seals cause the odor and the bubbles? Thats my next step, to reseal this IP.
My MPG's haven't changed, seem to get around 800'ish miles per tank, and the performance with this engine seems to be the same. I don't know if I'm being overly critical, but sometimes when its been driven for awhile, over an hour, it doesn't accelerate quite as well as when it's cold.
If not the IP seals, any other suggestions?
thanks
Steve
 

Campbellonh

Veteran Member
Joined
Jan 15, 2003
Location
New Hampshire
TDI
formerly:Passat, 96, white and 10 Jetta, white gold
Check the small lines that go from injector to injector, they can definitely leak and be hard to see, especially if you still have black braided covering style tubing. Feel the braided cover for wetness. Also, you may be having issues with your fuel sender. That happened to me a while back when I was having unexplained air bubbles. I don't remember exactly what was wrong with it, just that I couldn't figure it out. It took Chris Hill a couple of days of troubleshooting to determine the cause. Is it running rough at all, hard to start?
 

smos1

Veteran Member
Joined
Jun 28, 2008
Location
Seattle, WA
TDI
'96 B4V w/AFN swap, 2011 JSW with a leaking pano
All the fuel lines have been replaced, including the small lines you mentioned... and I've not seen any sign of leakage from them.
It runs fine, starts right up absolutely no issues.
 

Steve Addy

Top Post Dawg
Joined
Aug 7, 2002
Location
Iowa
TDI
97 Mk3
If it's leaking enough to smell then it has to be leaving a mark somewhere. There really should be some fuel under the car or a visible drip somewhere that you can see.

When the AFN was installed what happened to the 5th injector setup? was that left as part of the fuel system?

Steve
 

Mcgink

Veteran Member
Joined
Oct 15, 2004
Location
South of Boston MA
TDI
I-Red,"The Passat formerly known as Harlequin" 97 B4, a non VW GTDI too
I had a similar fuel odor on mine before a pump reaseal. Finally saw/found the leak one AM when the engine bay was cold on start-up. A very visible fuel leak seeping from the pump that would go away when the engine warmed up. Prob the thermal expansion helped seal it up when warm. Of course a closer look at the tripple hose under the pump revealed how diesel fuel turns coolant hoses into mush.
 

LLL

Veteran Member
Joined
Jul 12, 2006
Location
Europe
TDI
'95 Red Passat TDI 90hp 5 manual
Check the fuel filter "T" o-ring and filter hoses.
 
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