Belly tank breather lines

scott oz · 22nd April 2010, 10:57 AM

OK I’ve got two “belly/sill” tanks fitted to my 2001 TD5 110. I’ve just spent a considerable amount of time running separate breather lines. The previous set up was the breather lines “joined” to form one breather line to the fuel filler.

Because the tanks fill from a single fill point (standard) which has had braised a branch (1) where you position the pump hose and fill the belly tanks. The first belly tank fills then backs up the fuel line to a branch (2) which then flows across a pipe and fills the second belly tank.

The branch (2) point which allows the second belly tank to be filled once the first is full and backs up to the branch (2) is higher than both belly tanks.

So what was happening I believe was that as the first belly tank filled the fuel line fuel not only backs up the fuel line to branch (2) it also backed up the breather hose because the breather hose is lower than branch (2). So as it was a “joined” breather hose it filled with fuel there was no way for the air to escape from the second tank quick enough for it to fill properly.

So I’ve now run completely separate breather lines from each tank back to the fill point.

As the breather hose has to run/vent back to the main full point the hose has some “U” turns to clear chaise and body ribs which I believe will trap fuel. This is because when you fill the tanks you actually have to fill the fuel line all the way back to the fill point

Hope this is as clear as mud. So my question is how do you blokes vent your belly tanks without causing a fuel blockage in the breather lines? Or what would you suggest.

**JDNSW** · 22nd April 2010, 11:36 AM

I have never worried about whether there is a liquid trap low in the breather to my belly tank* - when filling, any liquid trapped in the line will be blown pretty quickly back into the filler, and when using, it will pretty quickly get sucked into the tank. I don't think there is much in the way of "U"s anyway, as it runs from the top of the tank between the chassis and the body, and tees into the original breather just below where it joins the filler.

John

*Single belly tank from the transfer case to the A-frame cross member and from just clear of the prop shaft to the LH chassis rail, bottom level with the bottom of the gearbox crossmember and with a skidplate.

**Bundalene** · 22nd April 2010, 03:45 PM

Like JD says, any fuel in the lines will blow back into the filler, as long as the run is reasonably flat. If you have a low trap, this could be a different story.

See the installation which we did a few years ago. No fill problems at all and all from one point. We can either fill the front 2 sill tanks separately by inserting the fill nozzle into the branch line.

http://www.aulro.com/afvb/projects-t...ill-tanks.html

Erich

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