Weber fuel leak

[S2K]

Hello all,
I'm looking for a bit of help here from from someone who knows their way round Weber carbs, namely twin 40's. I fired the car up the other day after spending the winter doing various jobs on it only to find fuel running out of the front barrel of the front carb. I've taken the trumpet out and pulled the auxillary venturi out and now I'm stumped. I've got an exploded diagram of a weber 40 dcoe but can't really see what could be the cause. Can anyone help please.
Andy.

[singlecoil]

I haven't looked inside a Weber 40, but I assume there is some kind of float chamber, which has a float valve which prevents too much fuel from entering. The first thing I would check is that that valve is functioning correctly, because it sounds as if it isn't.

[S2K]

O.K. that gives me a starting point. Thanks.

[thescamper]

Try giving the float chamber a tap, sounds as if the float has stuck. Either that or have you changed the fuel pump?

[S2K]

Haven't had a chance to try anything yet, hopefully tomorrow. I've not changed the fuel pump, why would that cause this problem?

[Sam_68]

singlecoil said:

I haven't looked inside a Weber 40, but I assume there is some kind of float chamber, which has a float valve which prevents too much fuel from entering. The first thing I would check is that that valve is functioning correctly, because it sounds as if it isn't.

Yep, there's a needle valve that the float operates (much like the ballcock on your toilet cistern). It's part number 8 on this diagram.

They have a habit of sticking and causing the carbs to flood, with exactly the results you've reported.

Dead easy to get to (just take the top off the carb, carefully drift the pin that forms the 'hinge' of the float out, then unscrew the needle valve)) and quite cheap to replace (about £11, IIRC). Sometimes they stick because they get gummed up with petrol residue when the fuel evaporates on cars that are infrequently used, or becuase a bit of crap has found its way in via the fuel (you do have a fuel filter, I hope?), but I tend to change them at the slightest sign of a problem because I'd rather spend £11 that get burnt alive!

Edited by Sam_68 on Tuesday 8th June 19:55

[Comadis]

depending on the age of the carbs the floats have been fabricated out of brass.

2pieces soldered togehter. sometimes the soldering becomes weak, than the float does fill up with fuel, therefore couldnt close the valve.

[S2K]

Thanks fellas, all this is very helpful.

[S2K]

O.K. I've now had the carb lid off, float is fine, taken out float valve and blown it through, reassembled and started the car and nothing has changed, fuel still running out. So it looks like a new valve is needed, can anyone recommend where to get one from. Thanks.
Andy

[singlecoil]

S2K said:

O.K. I've now had the carb lid off, float is fine, taken out float valve and blown it through, reassembled and started the car and nothing has changed, fuel still running out. So it looks like a new valve is needed, can anyone recommend where to get one from. Thanks.Andy

http://www.webcon.co.uk/Downloads/webcon%20Leg%20Dealer%20ad%202%20lo.pdf

whichever one you fancy

[S2K]

Thanks singlecoil.

[Mojocvh]

Some bloody good gen there, thanks guys.

Mo.

[S2K]

Ended up getting a service kit complete with needle valve from Eurocarb Ltd. (www.dellorto.com ) they do Webers as well. I ordered it on sunday and it arrived this morning, well chuffed. Fingers crossed that it solves the problem.
Andy