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MG MGB Technical - Fuel overflow

Need help. Just getting Old Dan back in operation after a layoff of several years. New points and plugs, rebuilt alternator and 1969B is running fine.

Suddenly, while running, gas pours out the lid of both front and back float chambers. Car keeps running OK, but I'm freaking out.

What causes this gas leak and how do I fix it?
Mike Kaylor

Sounds like sticking float needle valves in the float chambers causing the fuel to keep flowing into the chambers. If the car has been laid up this is the usual cause. You could try giving the chambers a clout with a screwdriver handle to see if they reseat but best to have a look in the chambers and check them by eye, also check the floats are not punctured and set correct.It might be crud holding them open so check that out as well when to open up the chambers.
Hope that helps

C J Bryan

Most likely build up. I had the same problem. If it were a puncture in the float I'd imagine they'd overflow immeadiately.

On HIF4's I removed the float covers, they were loaded. Cleaned just the covers and haven't had any other problems in over 5 years.
Phil Collura

Sounds like stuck float needles. Just need to clean out both float bowls completely and recommend replacing the needles. Easier done if you remove the carbs and work on them on the work bench. Even if the floats get stuck gas should only come out of the overflow tubes for safety, so checks that the overflows are working correctly.

Andy Preston

Thanks guys. This is the second time it has happened on the front float chamber and the last time it seemed to fix itself. This time, I took lids off both float chambers and made sure needles were clean. Seems to have rectified it again for the time being.

This is a labor of love. A new brake master cylinder, and I'll be on the road. I gave up on rebuilding it after the first circlip.

Thanks again.
Mike Kaylor

This thread was discussed between 24/07/2005 and 28/07/2005

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