flak monkey
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| posted on 24/4/09 at 07:50 PM |
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Leaky fuel tank breather
Another problem, I have a one way breather vent on the tank which seems to be dribbling fuel a bit now.
Its one of these
Linky
Which seems to just have a loose ball in it.
As I am running a return would I be best using a two way breather? (How they would work is beyond me!?) Or would one of these be better?
Linky 2
David
Sera
http://www.motosera.com
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minitici
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| posted on 24/4/09 at 08:48 PM |
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Where have you mounted the breather valve?
It really should not be immersed in fuel - normally fit in a line mounted to the tank above the normal fuel level.
It's designed to stop fuel when you turn the car over 
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flak monkey
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| posted on 24/4/09 at 08:59 PM |
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Its in a line well above the top of the tank. Issue is my return line is teed into the same bit of pipe.
I think a two way would also reduce the stress on the tank to prevent positive pressure in the tank?
David
Sera
http://www.motosera.com
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nitram38
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| posted on 24/4/09 at 09:42 PM |
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It has been mentioned many times by me.....you definiteley need two way breathers on all tanks, especially those with returns.
Been there, done that!
On a one way valve, air is drawn into the tank to replace the fuel that is pumped to your engine, but if it is returned to the tank, this air must
then be pushed back out. It can't do that so you end up with a pressurised tank.
Two way valves aren't cheap. Mine cost about £28 from thinkautomotive.
If you don't have a fuel return, you still need a two way breather as your fuel vapour expands during hot weather.
Neither of the valves you link too are any good as they are both one way.
A two way valve will only close if inverted.
[Edited on 24/4/2009 by nitram38]
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f1ngers
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| posted on 24/4/09 at 09:43 PM |
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I've got the same one from ebay in the end of the tank breather pipe and noticed a strong smell of petrol around the back of the car after
returning from SVA. I traced it to the breather and could see some petrol had dribbled out. I took it off and blew through it and it fails to seal
properly. It is mounted horizontally which may have contributed to the problem. The valve in the 2nd link looks like a better bet and I think I will
replace it with one of those.
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nitram38
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| posted on 24/4/09 at 09:46 PM |
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quote:
Originally posted by f1ngers
I've got the same one from ebay in the end of the tank breather pipe and noticed a strong smell of petrol around the back of the car after
returning from SVA. I traced it to the breather and could see some petrol had dribbled out. I took it off and blew through it and it fails to seal
properly. It is mounted horizontally which may have contributed to the problem. The valve in the 2nd link looks like a better bet and I think I will
replace it with one of those.
Don't, you are wasting your money.
You need a two way valve as I have already mentioned
Link to correct valve
[Edited on 24/4/2009 by nitram38]
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flak monkey
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| posted on 25/4/09 at 07:56 AM |
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Whats the consensus on drilling holes in the fuel cap to let some air in and out? Wouldnt stop a leak if you rolled the car but serves as a
breather...
David
Sera
http://www.motosera.com
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adithorp
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| posted on 25/4/09 at 08:06 AM |
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I've got the same one and get the same problem, but only with a full or almost full tank due to fuel surge in the tank. I'm replacing it
with one like Martin sugests.
Don't totaly agree with your argument though, Martin. The fuel circulating from the tank to the engine and back always returns the same or less
volume than leaves and as the fuel lines are always full(unless you run out) , it does both at the same time; Not draw some fuel and then return it
after a delay. As I see it, the need for a 2way is more to do with expantion of the fuel through temp'changes and the evaporation that occures
in the tank (and that will increase slightly with no pressure in the tank).
Modern tin-tops now run a closed system for emmision reasons. The gasses being stored in a carbon canister and draw into the inlet manifold, controled
by the ECU. These sysems usually result in positive presure in the tank. Thank god thats not been included in the IVA!
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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nitram38
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| posted on 25/4/09 at 08:48 AM |
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Trust me Adrian, your tank will pressurize for this reason, I've done it.
My tank would only show signs of slight pressure when left standing, but if left with the engine running, the tank would bulge and start blowing the
seals.
Drilling a hole in your fuel cap without a safety valve is ok unless your car is inverted or some passing smoker gets too close! 
After learning my lesson with a one-way valve, I'm using a two-way valve and a small filter on the Motaleira
[Edited on 25/4/2009 by nitram38]
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flak monkey
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| posted on 25/4/09 at 09:51 AM |
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My issue is i need a quick fix for today and tomorrow as I have another show to attend tomorrow then I can order a proper valve monday morning to fit
into my filler neck with a pipe take off.
Cheers,
David
Sera
http://www.motosera.com
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nitram38
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| posted on 25/4/09 at 12:08 PM |
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A quick fix is to remove the valve and create a U bend in some fuel pipe that goes down below your tank and returns to above it.
Not perfect but will offer some protection.
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flak monkey
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| posted on 25/4/09 at 04:44 PM |
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Vent doesnt seem to leak once i have under 3/4 tank so will keep the level a bit lower until i have a proper valve.
So one of the TRL67 from think auto valves would be suitable then? They work both ways letting air in and out of the tank properly?
I dont want to spend £30 on a valve for it not to do what I need!
Cheers,
David
Sera
http://www.motosera.com
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nitram38
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| posted on 25/4/09 at 05:18 PM |
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Best to call them as they made up the fittings for my pipes (I think I have 8mm).
It will save you faffing about.
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