How to Fix Fuel Leaking From Carb

[Nick Moore]

The floats themselves don't wear, although if they develop a leak they'll sit too low down in the chamber and not rise far enough to shut off the valves. The valves in the chamber lid do wear, opening and closing as the fuel level in the chamber rises and falls. I'm not sure how you can check for wear in the valves visually; they're cheap, so most people would just fit new ones.

If you fit a regulator, you should also fit a gauge to check that the regulator is delivering the desired pressure. It's probably worthwhile buying the gauge and adapter first - the current pump may be delivering the correct pressure after all and not need a regulator. Once you have checked the pressure and set it up properly, don't leave the gauge in there. The internals in some types wear with vibration and can start leaking fuel. 'Tis better to remove the gauge from the adapter and fit a blanking plug.

[JSBulmer]

I have the twin 150CD on my 68 GT6 and had a similar problem with fuel pouring out of the carbs.

All I had to do was to adjust the set screw at the base of the carbs.  No dismantling (except the air boxes).

What I ended up doing was to fully close the screw and then open it back up to its regular setting.  Am thinking that either an o-ring or a bit of debris had plugged off something and simply by adjusting the screws the problem went away.

jb

[Chambers]

Thanks, Ive just looked as its dry and it does seem to be coming from below as opposed to above so think its from the main jet part (bottom of page 42 rimmer bros) anyway I was going to try tightening it but I will loosen it and then tighten as you say.  Seems a bit awkward to get to though :-s

[James]

Chances are the O-ring has gone bad. Simple but a bit of a pain to replace.

[Chambers]

Well it would seem ive gotten to the bottom of it, and thats because its at the bottom of the carb.  Turns out that one of my main jets has the seal completely off, now Im not sure if I can fix it but if not I have some new ones coming in the overhaul kit.  Heres a photo of how it is at the moment, just a little pull with no pressure and it came out.  The otherside is not like this

[greenbonnie]

hi chambers. have you recently changed the fuel pump? i had the same problem. cured by fitting a pressure regulator. pete

[Chambers]

I havent but the previous owner may have, the problem has been there since I got the car.  Im going to fit a pressure reg, it should be in the post.

I have just tried to re-seal the pipe shown in the previous pic but have had now luck, the seals look a bit worn so when the carb kit comes I will use the ones out of there.  I just wanted to check as per the Haynes manual it goes screw -> seal -> washer?

[Chambers]

Looking at the SU HS4 instructions that are around the internet from SU it seems that it goes screw ->washer -> -> seal

Part 31, 32, 33

http://www.mgexperience.net/article/su-hs-inst.html

Can someone help me with this one as I dont want to put them on the wrong way

[greenbonnie]

hi chambers. these are notorious for leaking there. firstly buy a new rubber seal. then fit the metal washer then the rubber seal to the fuel pipe. hold these back on the spring, then push the pipe into the float bowl as far as it will go. then tighten the nut  holding the pipe in place. pete

[greenbonnie]

also make sure you have all old rubber seal residue cleaned out. pete

[Chambers]

Thanks, hopefully the seals should be coming today

So to clairfy it goes from the carb jet

pipe with spring over it -> old nut -> new washer -> new seal

everything is slid over the pipe and then pushed into the bottom of the float bowl and the nut is tightened?

[James]

Something like that - though you may need to try a few times to get it to seat properly.

[Chambers]

great stuff, lets see how this goes when the postman gets here :)

[rhodes]

Yes, you have to load the bits and the rubber washer onto the pipe and then push the lot into the hole.  You will probably have to push the rubber (with the pipe in it) with a prodder. You cannot easily push the pipe into the rubber seal when this is already in the hole.

[Chambers]

Instead of just changing the seals I completely changed the jets as the washer/seals were already on the new ones.  It seems to have fixed it which is good :-)

[bob dunn]

i hope this helps you to see what is going on

http://www.sucarb.co.uk/TechnicalDetail.aspx?id=39