Fuel tank mystery barb

A while back now I topped off my tank, parked to do some shopping, and came out to find a river of diesel flowing from my car. The source of the leak was somewhere on the filler neck, and once it dropped below there it of course stopped.

Upon inspection, I could feel (and see, with a mirror) a downward-facing hose barb on the neck that has no hose, but I do not see this shown on the Bentley tank diagram, nor can I figure anywhere a hose would go to from there! The other vent hoses are accounted for, I'm just not sure what's going on with this one. Does anyone have a better diagram, or a photo of a dropped tank showing the hose routing?

If you’re seeing a barb with no hose attached, I’d say look harder. It may be possible the hose got brittle and broke, but you should still have a dangler.

-Todd

Wait.... the black, rubber fill neck surround has a drain for spilled fuel. Is this what you’re seeing?

-Todd

i had this happen once to me. i filled up the car TO THE TOP after the foam settles, always have, always will. ( i use 5 gallon cans filled up at truck pumps for the discount!)
i did that at night, it was about 60*F, wake up the next morning, FUEL EVERYWHERE, about a 4 foot circle worth of wetness. the temp had jumped up to 95*F and the fuel expanded, the cap was not on all the way this time and some fuel ran out, on to the tire, and on the ground from the fill neck boot drain.

not sure if this is what happened to you, maybe parking on a hill that changed the fuel level on the tank?

double check your fuel cap and test it for pressure. you can do this EASILY, take the fuel return line from the filter, connect a air line to it at 10psi, it should hold, but it should let air out in a hissing sound at 12 or 15 psi,
i think, i cant remember the pressures off the top of my head, maybe its less, someone can confirm that or explain it better

There is no remnant hose, and it is most certainly not the spillage drain. It's on the backside of the fill neck, about 3/4 of the way up. I looked at it with an inspection camera but it's too tight to get an overall shot.

Is it maybe a vent mod to fill more fuel into the tank? I never did one but maybe the previous owner did?

I've had the car for fifteen years, and have almost always exclusively topped it off completely. It has a ventectomy, but I did it right after I got it. The fuel is leaking from the area of the indicated barb, not from the cap or elsewhere.

If there's a barb with nothing on it then you have a missing hose.

Filling completey (with ventectory) and then parking the car is a bad idea.

Steve

Yes, I am aware there is a missing hose, that's why I'm asking if anyone knows or has an image of the routing. Obviously I know where one end goes.
This is looking down from the top of the wheel well.

This might help you figure out what's going on.


Steve

Thanks for the diagram. Unfortunately, it doesn't solve what's going on. Clearly I'm missing hose # 31, but I've dropped the tank enough to look around and there still is no other place for it to attach. There is no 2A style holding tank, and no secondary vent on the tank itself. Could there have just been a cap/plug that's missing from this tee?

Previous owner may have had a busted fuel tank, and replaced it with a non-TDI tank. Hose 31 attaches to reservoir 2A, which has Model Data of "MEX". There are other Model Data notes for "diesel eng", which apparently does not apply to either the hose or reservoir. That may explain why nobody else here (yet) has any familiarity with this problem.

I suggest you plug the open barb with JB Weld or something.

Maillemann said:

Thanks for the diagram. Unfortunately, it doesn't solve what's going on. Clearly I'm missing hose # 31, but I've dropped the tank enough to look around and there still is no other place for it to attach. There is no 2A style holding tank, and no secondary vent on the tank itself. Could there have just been a cap/plug that's missing from this tee?

Click to expand...

You won't solve what's going on until you drop the tank and find the hose that's become detached, that's the long and short of it.

I'd run the tank down to zilch, then pull the lines at the sender unit and drop the tank. There's maybe a screup up high at the neck and the straps, otherwise there's nothing else holding it in.

Steve

I dropped the tank enough to look and feel around and can't find any other place where a line would go. So I checked on another '96 Passat and there's no hose coming off the tee either.