simonk
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| posted on 22/6/09 at 09:57 AM |
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Fuel Tank Breather
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
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richardh
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| posted on 22/6/09 at 10:05 AM |
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best to hava one. not cheap for the proper ones but a good investment
Time for a change!
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iscmatt
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| posted on 22/6/09 at 10:18 AM |
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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
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blakep82
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| posted on 22/6/09 at 10:18 AM |
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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]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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BenB
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| posted on 22/6/09 at 10:21 AM |
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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.
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Steve G
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| posted on 22/6/09 at 10:40 AM |
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quote:
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.
I didnt think it would matter with fuel being returned myself to the valve required. With the engine running there will always be more fuel pumped out
of the tank than is being returned and as its a continuous cycle, there has got to be a continuous net reduction in fuel level. With the ignition on
but the engine not running then the fuel will just circulate with no reduction in fuel level.
Or have i missed the point here? I'm going injection myself so interested to gain some clarification on this
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simonk
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| posted on 22/6/09 at 11:10 AM |
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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
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simonk
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| posted on 22/6/09 at 11:17 AM |
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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
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iank
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| posted on 22/6/09 at 11:32 AM |
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nitram38 is pretty convinced you need 2 way breathers in this thread
http://www.locostbuilders.co.uk/viewthread.php?tid=111829
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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wilkingj
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| posted on 22/6/09 at 11:37 AM |
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£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.
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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DavidM
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| posted on 22/6/09 at 12:22 PM |
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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
Proportion is Everything
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matt_gsxr
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| posted on 22/6/09 at 12:47 PM |
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think automotive are the cheapest for these, if I remember correctly.
less than £30 but still £20
Matt
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Madinventions
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| posted on 22/6/09 at 12:51 PM |
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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.
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myke pocock
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| posted on 22/6/09 at 01:02 PM |
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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.
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