Dave J
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| posted on 3/2/06 at 03:09 PM |
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fuel tank breather
Hi All,
I have a small outlet from the top of my fuel tank, which is obviously for a breather pipe.
Can anybody tell me at what level the end of the pipe should be, ie, above the tank, below or what?
Also, should it have some sort of vapour trap/valve on the end to stop fumes escaping?
Many thanks for your help.
Dave
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flak monkey
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| posted on 3/2/06 at 03:13 PM |
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Best thing to do, or should that be simplest, is to take a bit of fuel hose and bend it through 180deg. Make the long end long enough to hang below
the bottom of the tank. The short end should attach to your breather. This way if you ever have the misfortune of ending up upside down you wont have
petrol leaking from your tank.
David
Sera
http://www.motosera.com
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bob
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| posted on 3/2/06 at 03:15 PM |
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I've just got a one way valve on the top of mine,works fine and went through SVA ok.
[Edited on 3/2/06 by bob]
 
Rescued attachment MK Indy build pics 072.jpg
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andyharding
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| posted on 3/2/06 at 03:43 PM |
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I used one of the 1 way valves on the stick Pinto induction system.
Are you a Mac user or a retard?
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NS Dev
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| posted on 3/2/06 at 03:51 PM |
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Either of the above will do the trick.
For what it's worth I usually use a piece of copper/kunifer brake line looped around the tank and terminated with an open end just below the
tank.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Dave J
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| posted on 3/2/06 at 04:10 PM |
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Thanks for the quick replies all, they all sound great ideas.
I'll probably combine the loop pipe and the valve.
Incidentally where can a buy a one way valve from?(save me trawling the net).
Thanks again.
All the best
Dave 
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NS Dev
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| posted on 3/2/06 at 05:33 PM |
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Think Automotive or Rally Design, both net based
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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RazMan
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| posted on 3/2/06 at 11:31 PM |
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Harris performance do a suitable one for £7.23 + vat 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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cornishrob
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| posted on 4/2/06 at 09:54 AM |
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laying in bed last night i actually had a thought about this.
with the one way valve nothing should leak, but im never one to take chances.
problem i see is if the car lands upside down it wont let petrol out, but what if the car lands on its side and the one way valve fails.
petrol everywhere!
My suggested answer to this is place the breather pipe along the length of the tank before it exits down to the ground. so that whatever way you land
the petrol will have to flow uphill to leak.
NS devs idea of looping around the tank is a good idea but you still have the possability of a leak if the cars on its side.
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britishtrident
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| posted on 4/2/06 at 11:25 AM |
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Oneway valve works on head of pressure --- won't leak no matter what way up the car is .
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RazMan
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| posted on 4/2/06 at 11:26 AM |
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quote:
Originally posted by cornishrob
NS devs idea of looping around the tank is a good idea but you still have the possability of a leak if the cars on its side.
But that depends if you loop around north/south or east/west 
quote:
Originally posted by britishtrident
Oneway valve works on head of pressure --- won't leak no matter what way up the car is .
But it wont allow air to vent fron the tank either - your tank will be inflated and go pop!
[Edited on 4-2-06 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Dave J
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| posted on 6/2/06 at 12:08 PM |
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Thanks again for the info guys, it's a great help.
quote:
Originally quoted by RazMan;
But it wont allow air to vent fron the tank either - your tank will be inflated and go pop!
Surely the one way valve will allow air into the tank when the pump draws the fuel out, so I cant see how the tank would either implode or explode.
On filling the tank the displaced air would rise up the filler. Have I missed something or am I being too simplistic?
Thanks again.
Dave.
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Schrodinger
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| posted on 6/2/06 at 12:49 PM |
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You should use the proper valve which lets air/vapour flow either way but does not let petrol through. There needs to be a way of air entering the
tank as you use the fuel and to allow air out as it expands when the car is standing on a hot day.
I did just loop my breather pipe over as others have suggested, however, I filled the car to the brim one day and drove off and home with a couple of
tight turns and parked the car in my drive and when I came back a couple of min later the fuel was syphoning out of the tank.
Keith
Suffolk
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RazMan
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| posted on 6/2/06 at 01:12 PM |
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quote:
Originally posted by Dave J
Surely the one way valve will allow air into the tank when the pump draws the fuel out, so I cant see how the tank would either implode or explode.
On filling the tank the displaced air would rise up the filler. Have I missed something or am I being too simplistic?
As Schrodinger just said, a one way valve will not allow for expansion gases to escape - I am suprised by the siphoning though
There are some dedicated tank valves that operate 2 ways (not exactly sure how) but like all good things they are a bit pricey. Think Auto do one
(TRL67) for around £25.
A range of fuel tank valves that allows 1)air in to replace fuel used, 2) air out due to heat expansion. 3) a positive shut off to prevent fuel
escape, due to splashing or even roll over. This is achieved by a two ball system, one hollow plastic, one solid steel.
[Edited on 6-2-06 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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NS Dev
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| posted on 6/2/06 at 01:22 PM |
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quote:
Originally posted by Schrodinger
You should use the proper valve which lets air/vapour flow either way but does not let petrol through. There needs to be a way of air entering the
tank as you use the fuel and to allow air out as it expands when the car is standing on a hot day.
I did just loop my breather pipe over as others have suggested, however, I filled the car to the brim one day and drove off and home with a couple of
tight turns and parked the car in my drive and when I came back a couple of min later the fuel was syphoning out of the tank.
Keith
Suffolk
Sorry but this is physically impossible unless the end of the breather pipe is below the fuel level!! (which it most certainly should not be!)
What you probably had was some residual fuel trapped in the loop of pipe which was being pushed out as warmth caused vapour pressure in the tank.
Most fuel breathers will leak a small amount.
Many production cars don't have any fancy rollover valves, my sierra XR4x4 doesn't for example.
Britishtrident - I know what you are saying about rollover valves, but in my experience, because they hardly ever close, the first time they do they
nearly always leak anyway!!!!! The ball seat usually either has pitting or dirt on it or doesn't quite seal properly for some reason. Certainly
we rolled the rally car 6 times in 6 seperate events over 2 years and the "no leak" megabucks valve leaked every time!!!
The comments about ending up on your side with the breather pipe leaking are valid with the curly pipe idea, you just have to be imaginative with the
routing and then make the odd offering to somebody upstairs (if you believe in all that) just in case!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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Dave J
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| posted on 6/2/06 at 01:22 PM |
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Ah now that clears it up nicely, thanks guys
All the best,
Dave
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Dave J
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| posted on 6/2/06 at 01:28 PM |
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But then again!!
Better get my hassock out!
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DarrenW
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| posted on 6/2/06 at 03:32 PM |
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i fited one way valve to breather pipe then mounted that higher than the tank inlet. I figured that most of the time the car isnt upside down and more
often than not you can fill the tank and part way up the neck - hence higher is better. SVA man was happy with this.
As an aside hijack - does everyone else have bother filling the tank - pump keeps clicking off. Neck is 90deg flexi to back panel mounted cap.
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Jubal
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| posted on 8/2/06 at 07:09 PM |
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quote:
Originally posted by DarrenW
i fited one way valve to breather pipe then mounted that higher than the tank inlet. I figured that most of the time the car isnt upside down and more
often than not you can fill the tank and part way up the neck - hence higher is better. SVA man was happy with this.
As an aside hijack - does everyone else have bother filling the tank - pump keeps clicking off. Neck is 90deg flexi to back panel mounted cap.
Mine's the same. PITA. It even spits fuel back out when I fill slowly from a jerry can. The breather pipe is an open tube at present so there
shouldn't be any issue with escaping air.
I'm considering fitting a slightly longer flexi hose to see if that helps, especially as inspired by this thread and the shower of petrol
I've been giving people who follow me on track I bought an inline one way valve to fit into the breather pipe so cutting off that as a route for
escaping air. Let me know you find a cure.
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RazMan
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| posted on 8/2/06 at 08:10 PM |
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quote:
Originally posted by Jubal
I'm considering fitting a slightly longer flexi hose to see if that helps
If you mean the corrugated style rubber hose - that could be your problem because the flow is very slow due to the corrugations.
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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Jubal
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| posted on 8/2/06 at 09:41 PM |
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quote:
Originally posted by RazMan
If you mean the corrugated style rubber hose - that could be your problem because the flow is very slow due to the corrugations.
Thanks but it's the flexible rubber lined stuff with a steel spiral running through it.
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Jon Ison
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| posted on 8/2/06 at 09:52 PM |
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couple of things too think about........
I would defo fit a non return but also fit it as close too tank as poss, if the pipe gets ripped off in a collision then you have an open end
again.
filler cap, if this is fastened too the bodywork and the bodywork gets hit, damaged or ripped off in a collision then you have around a 2" open
end into your tank, I have seen this too an unfortunate soul, if your doing track days in your car i would be tempted too look at your filler cap
position and maybe even if its only a road car too, I know these aerocaps look nice on the rear panel but imagine what would happen if you got one up
the rear ???
Ive had a fair few offs in my time, the one at cadwell would have seen the filler cap off if it had been fastened too the bodywork and the more recent
one on the road would have had the filler cap off too.
Food for thought.
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Jubal
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| posted on 8/2/06 at 10:37 PM |
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Thanks for that sobering thought!
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Jeffers_S13
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| posted on 3/7/06 at 10:43 AM |
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quote:
Originally posted by NS Dev
Either of the above will do the trick.
For what it's worth I usually use a piece of copper/kunifer brake line looped around the tank and terminated with an open end just below the
tank.
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Jeffers_S13
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| posted on 3/7/06 at 10:44 AM |
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quote:
Originally posted by NS Dev
Either of the above will do the trick.
For what it's worth I usually use a piece of copper/kunifer brake line looped around the tank and terminated with an open end just below the
tank.
How is it connected to the fuel tank ?
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