Hello all

A nice gentleman stopped me yesterday to let me know that I was chucking fuel out on the road on lefthanders. I know that fuel comes out of the breather when the tank is brimmed - but my question is do I need the breather ? If I have a vented cap is that enough ? How do I know if my cap is vented ?

Thanks all, can't afford to be slinging fuel down the road .........

Simon

best to hava one. not cheap for the proper ones but a good investment

had this problem too, changed the routing of the breather pipe, i know have it going straight up from the tank, just get it is high is it will go and stick a breather on the end of the pipe, never had a problem since

i think you can get ones that let gas out, but not liquid. they're the ones to go for, but not cheap

actually, thinking about it, my breather (not used yet though) is a one way valve, lets air into the tank to take the space of used fuel, but doesn't let anything out. any a few quid. like this one? http://www.edsmotorsport.co.uk/one-way-valve-70-p.asp

[Edited on 22/6/09 by blakep82]

If you're running carbs then you can just get a simple one-way valve. I got mine from Merlin. Cost about 20 quid.

If you're running injection then things get a bit more complicated because your return line will be putting fuel back into the tank so you need to be able to compensate for that. Then you need an air/fuel valve which costs.

quote:

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Originally posted by BenB
If you're running injection then things get a bit more complicated because your return line will be putting fuel back into the tank so you need to be able to compensate for that. Then you need an air/fuel valve which costs.

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Thanks all for your responses. I'm running a carb and had followed the build manual and put a pipe on the breather tail and run it up to a U bend at the highest point I could, then straight down to the road. When it's full it just chucks out fuel on even modest left handers.

If I fit a one-way valve what deals with fuel expansion ?

Thanks
Simon

Thanks all, thisk I answered my own question by looking at the Merlin site - they do an 'air out, air in, no fuel out' valve that looks like the right job - 30 quid though, mind you I must be chucking a few quid down the road after every fill up !!

Thanks again
Simon

nitram38 is pretty convinced you need 2 way breathers in this thread
http://www.locostbuilders.co.uk/viewthread.php?tid=111829

£34 is a small price to pay for not having fuel sploshed about in the back of the car (Let alone on the road). Just one spark and you have a fuel fire by the fuel tank.... Not good!

Best play safe with these things.

Still... the topic serves as a reminder to those currently building, and those who didnt put one on.

Admittedly I only have a cheap one way valve fitted as high as I can get it. Never had any leakage however much I chuck it about.

You can never be too safe.

I had this problem and installed a small inline fuel filter in the breather pipe about 4 inches from the tank. It stops the fuel syphoning and cured it for me. Cheap and allows breathing in both directions.

David

think automotive are the cheapest for these, if I remember correctly.

less than £30 but still £20

Matt

Well here's a Locost solution: Go to a scrapyard, find a fuel injected vehicle and take the vent from the top of it's tank. I'm using the 'rollover valve/vent' from a 96 P Fiesta with no problems. Normally, the outlet of this is fed to a charcoal filter which is vented into the inlet manifold by the ECU. Sounded too complicated to me so it's now got about 4" of fuel hose on it and one of those 'noise reducers' as used on pneumatic systems to act as a dust filter. I've hung it out around some roundabouts, driven like a mad fish and there's no trace of vacuum in the tank or fuel around the breather.

Like I say, it's a Locost solution - I certainly didn't like the idea of paying £30 for one of those red anodised jobs when a 'free' bit of plastic from the donor sorted it out.

Ed.

Here's an even lower Locost solution. For SVA I drilled a hole in the inlet pipe from the fuel filler cap. I set a Nutsert into that. Then with a length of brake pipe, end flaired to make it look neat, I wound it onto a pipe about three times into a coil shape then glued the plain end into the Nutsert with Araldite. Passed SVA as a breather.