Flooding carbs - HELP!

[James Atkins]

Can any one HELP?

I had my carbs sorted out at Summit MG, ran OK on way back from Summit, and again on another run out, but on the 3rd trip, the same problem happened i.e. petrol coming out of the carbs! Summit have replaced needles and jets and cleaned carbs.

I have had conflicting advice from the MG Owners club, Technical advised me to fit a fuel regulator, but when I phoned today to order the parts, they told me to check to see if the needles are sticking? as they should have been oiled before fitting? and not put in dry, and that I shouldn't need a fuel regulator?

Now I am totally confused with it all, and just want to get the MGB working again - Summit MG can't get it back in until 5th or 6th Jan, any advice/experience of the same problem, would be much appreciated!

Thanks, Jim

[Peter Cresswell]

If you a standard SU fuel pump then you shouldn't need a fuel pressure regulator.
Have you done any work to the fuel system recently (other than the work at Summit MG) - like new pipes or replaced the tank, or more likely in the contex of your problem had the tank repaired? All these could have allowed particles to be in the fuel that will cause your problem.

Flooding is usually caused by sticking needle valves in the float chambers (not the needles and jets in the piston of the dashpot) which don't cut off the fuel supply when the fuel level is at the correct height. There are several reason why this happens (with suggested cures):
1. Worn needle valves - fit new valves with VITON tips.
2. Dirt in the fuel - it only needs a tiny speck of dirt to stop the needle valve closing properly. Fit an in-line filter.Better is to fit two filters, one before the pump, and a second just before the feed to the Carbs.
3. A Punctured float which then sinks in the float chamber - Check there is no fuel inside the floats. If there is fit a new float.
4. Do you still have original flexible fuel pipes or flexible pipes fitted more than 15 years ago? These are made from reinforced rubber and will rot with modern fuels. This has become more of a problem since 5% Ethanol (E5) is now in all Super Unleaded fuel and will become 10% (E10) in the future. The bits of rubber then flake off the inside of the pipe causes the needle valves to stay open. Fit flexible fuel pipe marked 'Suitable for all fuel types' or 'Suitable for E10 fuel', and fit fuel filters.

Flooding is an eternal problem with SUs, but the HS type fitted to the MGB are less prone to it than the earlier H type carbs fitted to MGAs and T-Types.

Burlen Fuel Systems now manufacture SU carbs so I suggest intitally you take a look here:
http://sucarb.co.uk/technical-carburett ... s-flooding.

One last thing is to make sure you have pipes connected to the overflows that route any flooding petrol well away from the exhaust system

[James Atkins]

Thanks for the info Peter - I do have standard SU fuel pump, no other work done other than that at Summit. In answer to other questions:

1. Need needle valves fitted - Viton to cope with richer fuel.

2. In-line fuel fitted by Summit before the feed to the carbs (which were all cleaned)

3. Carbs and float have been stripped by Summit

4. The original fuel pipes have also now been replaced by Summit so are all new.

I think rather than try and fix it myself, I will let Summit have it back to try and sort it out - I just hope it's not something that is going to take a while to put right!

[Graham Dix]

Hi James, Summit seem to have done all the correct work to rectify the original problem. The advice re oiling prior to fitting the needle valves is wrong. You should not need a regulator with a standard SU pump. Are both carbs flooding or just one? I can only think that a piece of debris in the fuel has partially blocked one of the needle valves but best let Summit rectify the problem. Regards Graham

[James Atkins]

Hi Graham

Yes, both carbs are flooding - it shouldn't have dirt from the fuel as Summit also fitted an in-line fuel filter, unless something has got through? I did give the carbs a tap yesterday to see if it would maybe dislodge any dirt/debris, but as soon as I started her she flooded so I am going to leave it now and let Summit have it back to rectify, just annoying as I wanted to take her to Brooklands on New years day, but there you go, that's all the fun of owning a 'B!

Jim

[James Atkins]

Hi

Just to let you all know the B is up and running, thanks to Ben the technician at Summit MG .
They had to fit two new carb tops and modified stay up (black?) floats from MGOC and my fuel regulator.
Took her out today and she is just purring...