Fuel tank breather

[roseytvr]

Having binned the carbon canister I am using the fitting on the top of the tank by the filler neck as a breather with the pipe coming out of the bottom of the car through the drain holes in the boot. problem is when I fill it up petrol runs out of the pipe and I have a substantial increase in petrol smell when driving. All pipes have been renewed and there are no leaks. Do I need to vent the tank or does it breather through the filler cap?

[DarkMatter]

I don't think that it breaths through the filler cap, some people put a cut in the rubber seal of the filler cap to allow it to breath.

I tried running without a carbon canister and got a petrol smell too, eventually I decided to put the carbon canister back and that got rid of the petrol smell.

If you are trying to stop the fuel tank banging which can occur I read a thread recently where someone replaced their roll over valve with a new one which stopped the banging.

[Crafty_]

You could use one of these:



This is a two way valve - it allows air to escape the tank to aid refuelling and/or expansion, but it also allows air in to the tanks to replace used fuel.

Its made by a company called newton industries but both ATL and Mocal re-sell them. About £50: http://www.merlinmotorsport.co.uk/p14603/INLINE-BR...

Someone used one a Noble here: http://www.pistonheads.com/gassing/topic.asp?t=107...
and here: http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Now, that last link the guy uses this valve and also a one way valve to stop petrol leakage, but from what I can work out the TPV8 will not let petrol out, but I can't find where I read that now! So you may want to check if you need to use a one way (or rollover) valve too

I think Merlin have a decent price, but check this out.
ATLTF-AF-009 £60 odd before VAT. note the markings on the body in the picture http://www.demon-tweeks.co.uk/motorsport/fuel-tank...

Mocal MOCPTV8 £41 before VAT http://www.demon-tweeks.co.uk/motorsport/fuel-tank...

Same flipping thing!

[roseytvr]

Thanks for that Mark - all interesting stuff. The link below confirms the breather valve does not let fuel past so I am assuming that is sufficent for my requirements.

http://www.demon-tweeks.co.uk/motorcycle/fuel-acce...

But, heres the thing! If it allows air out and allows air in all it effectively does is stop petrol coming out? If it is breathing out presumably I will still get the smell through the end of the outlet pipe so I guess I need to divert the pipe away from the drain holes in the bottom of the boot as this is where the fumes will be coming into the cockpit via the boot IYSWIM.

[Julesprivate]

I had a Buell (motorcycle) that did the same thing, US versions had a carbon canister installed but UK ones vented to atmosphere (and stank)..

I just added a long pipe with an inline filter that unscrewed, unscrewed that and filled it with kitty litter... You have to change it every so often but it does work...Especially the "fragranced" kitty litter.

TBH though all that does is replicate the carbon can you took off...

You can use charcoal too...

[Sardonicus]

I vent to atmosphere with just a large Nissan fuel filter at the end of the breather in the same location as the Carbon Canister to keep the gunk out ..... no smells or odours

[davep]

The fuel tank breather pipe on the pre-cat Griffs is routed down and out of the same aperture as the pump feed fuel hose into the n/s rear wheel arch. The exit of the breather pipe is curved upwards into a central vertical position high up in the wheel arch and is cable tied to an upright on the rear chassis. Might be a better option than straight down and out through a boot drain.

[roseytvr]

davep said:

The fuel tank breather pipe on the pre-cat Griffs is routed down and out of the same aperture as the pump feed fuel hose into the n/s rear wheel arch. The exit of the breather pipe is curved upwards into a central vertical position high up in the wheel arch and is cable tied to an upright on the rear chassis. Might be a better option than straight down and out through a boot drain.

Does it vent through any valves/filters or is it simply a hose pipe from the tank to the top of the wheel arch?

[davep]

roseytvr said:

Does it vent through any valves/filters or is it simply a hose pipe from the tank to the top of the wheel arch?

Originally there was no filter or valve fitted but might be an idea to fit a small filter (there's not a lot of room in there though). I think the principle is that any fumes in the arch are quickly wafted away by the action of the rear wheel. It's best to keep the boot cavity fume free since any smells in there seem to get quickly drawn into the cabin.

[carsy]

This shows a picture of the roll over valve breather thing on a pre cat. From there the pipe vents into the top of the wheel arch as already stated.

[roseytvr]

Magic gents thanks, I am now on the case! It's good on here ain't it!