daniel mason
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| posted on 29/1/11 at 10:15 PM |
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can i use a standard non return valve as a fuel tank breather?
as above is a standard none return valve ok as a fuel tank breather/vent? they dont let liquid through unless under pressure so it would seem they are
ok?
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daviep
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| posted on 29/1/11 at 10:53 PM |
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quote:
Originally posted by daniel mason
as above is a standard none return valve ok as a fuel tank breather/vent? they dont let liquid through unless under pressure so it would seem they are
ok?
What exactly is a "standard" non return valve and why would it let flow through under pressure?
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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prawnabie
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| posted on 29/1/11 at 11:02 PM |
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The "proper" one is available from merlin or think automotive - it is a two way valve that lets the tank suck air in and vent air out
whilst not letting fluid out in the event of a roll
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daniel mason
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| posted on 29/1/11 at 11:06 PM |
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i mean a non return valve. it wont let fuel through unless its pressurised so in the event of a roll it would not leak. it would not suck air back in
though,but obviously would let it out!
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daviep
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| posted on 29/1/11 at 11:21 PM |
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quote:
Originally posted by daniel mason
i mean a non return valve. it wont let fuel through unless its pressurised so in the event of a roll it would not leak. it would not suck air back in
though,but obviously would let it out!
Sorry I'm lost 
A non return valve allows flow in one direction and stops it in the other regardless of pressure in either direction.
Sorry not to be any help
Davie
“A truly great library contains something in it to offend everyone.”
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daniel mason
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| posted on 29/1/11 at 11:25 PM |
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it does allow flow in one direction, but the one i have only allows prssurised flow in one direction! i have seen those on merlin and cant see what
they do, that mine doesnt?
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Davegtst
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| posted on 29/1/11 at 11:25 PM |
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You really need it to vent air both ways but not let fuel escape. As you are using driving using fuel you will be creating a vacuum in the tank so
you would need air to enter the tank to stop this. On hot days petrol will expand which can create large ammounts of pressure in the tank. If the
tank is not vented when you open the cap you may get covered in petrol as the gases rush to get out.
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daniel mason
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| posted on 29/1/11 at 11:38 PM |
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ah! thats the response i was after. my valve is no good then. i bought it from cbs and it said it can be used as a fuel tank breather. but its not the
same as the merlin ones! cheers mate
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daviep
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| posted on 30/1/11 at 10:17 AM |
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quote:
Originally posted by daniel mason
it does allow flow in one direction, but the one i have only allows prssurised flow in one direction! i have seen those on merlin and cant see what
they do, that mine doesnt?
That's much clearer, what you have is pressure relief valve.
Davie
“A truly great library contains something in it to offend everyone.”
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RazMan
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| posted on 30/1/11 at 10:40 AM |
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I have used a couple of these on my tanks ....
Fuel tank cap breather Gold KTM petrol vent UK Seller on eBay (end time 20-Feb-11 18:46:49 GMT)
The valve allows air into the tank but stops fuel escaping - not perfect but definitely more Locost than the Merlin solution 
[Edited on 30-1-11 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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daviep
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| posted on 30/1/11 at 12:56 PM |
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The other truly locost option is a piece of hose. If the breather connection is on the top of the tank at the front you need to bend the hose through
180 degrees and run it down to the bottom of the tank at the back then bend it through 90 degrees and run it across to the other side of the car.
Kind of like this (excuse my crap paint skills  )
Davie
“A truly great library contains something in it to offend everyone.”
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