vindicator
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| posted on 18/10/07 at 01:12 PM |
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Petrol tank breather valve
Hi All,
On my tank the breather pipe is at one end of the tank sitting on top. I then have a piece of rubber tubing connected that can only extend upwards
upto 3 inches before it hits the body work and needs to bend down.
If the tank is fairly full and I go round a bend the fuel heads towards the breather pipe and then spills out down by the half shaft of the drive
wheel.
The fuel filler cap is a tight fit and will not let air past. So, what I need is a valve that does not let petrol thru one way, but lets air past to
get into the tank.
Has anyone used any of these valves or got any other ideas......
 
non return valve
[Edited on 18/10/07 by vindicator]
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BenB
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| posted on 18/10/07 at 01:21 PM |
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Simplest thing would be a tip-over valve. That should do the job. Merlin motorsport do some (relatively) cheap in-line ones...
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BenB
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| posted on 18/10/07 at 01:22 PM |
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http://www.merlinmotorsport.co.uk/FUEL-SYSTEMS-Tank-Breather-Valve/c26_215/p3555/BREATHER-VALVE-1/4-IN-LINE/product_info.html?osCsid=7765673068dec5712
8bfd92cf80120d0
Don't remember paying that much though!!
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the_fbi
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| posted on 18/10/07 at 01:25 PM |
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Mocal / Think Auto do them for around £10 iirc
www.thinkauto.com
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nitram38
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| posted on 18/10/07 at 01:26 PM |
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You need a two way valve if you have a fuel return, otherwise your tank will pressurize.
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RazMan
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| posted on 18/10/07 at 01:56 PM |
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I had an identical problem and fitted a cheap alloy fuel filter in the breather pipe. This acts as a kind of buffer - the odd surge caused by sloshing
is absorbed by the filter and drains back into the tank.
I originally had a breather valve fitted on each fuel tank but this caused problems as it was too restrictive and caused airlocks (one tank still had
10 litres when the gauge in the other tank read empty) I found that an unrestricted pipe worked fine but leaked under filling conditions and hard
accelleration / cornering.
When you route the breather, make sure you go as high as possible, even loop it around the tank and exit below the bottom of the tank. This makes sure
you don't leak fuel if you roll the car 
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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vindicator
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| posted on 18/10/07 at 02:21 PM |
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Thanks to the_fbi post, found the thinkauto catalogue very interesting......
Razman...fantastic....I bought a cheap filter months ago and found it was the wrong one to use for injection engines....so it has been sitting on the
shelf in the garage....I can use this.....I'll try it to night when I finish work and let you know....
Thanks
TimR
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andyharding
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| posted on 18/10/07 at 04:55 PM |
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Go and have a look in the scrappy at old cars with dizzies. These often have one way valves inline with the vacuum advance. I used on from my donor
Sierra and don't have any probs with fuel leaking.
Before this I tried the one way valve from the brake servo but my fuel pump couldn't suck hard enough to pull air past so the engine cut out
after 15 mins, take of the fuel cap and replace and it was good for another 15 mins.
Are you a Mac user or a retard?
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RazMan
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| posted on 18/10/07 at 05:15 PM |
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A one way valve is not a good idea because the tank needs to:
- Vent pressure when warm
- Let air in to replace fuel
The two way valves are more sophisticated than most people realise ... but expensive.
[Edited on 18-10-07 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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zetec
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| posted on 21/10/07 at 07:25 AM |
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I fitted one from a trials bike, allows slow flow one way to let air in to replace used fuel, and slightly better flow the other way to allow air only
out, works a treat and cheap.
" I only registered to look at the pictures, now I'm stuck with this username for the rest of my life!"
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