MG Car Repair: Gasoline dripping, charcoal canister, overflow pipe

Question
Hi Howard,

1968 MGB with the GF engine and HS4 SU carburetors.  Today I was installing seat belts, and I thought I would do it with the radio on  (I've added a wire to it so I can play my MP3 player through it...), so of course the ignition is on, and the fuel pump is pumping.  I did disconnect the (+) coil wire before switching it on.  About 20 minutes into the job I smelled gasoline.  I saw the puddle on the garage floor, and it was rapidly dripping from the front carburetor overflow pipe.  Does this mean I have a float/needle valve problem?  If so, is this a repair I can do with the carburetors on the motor, or do I need to pull them?


Thank you in advance for any and all information!

Regards,
Dan


Answer
Hi Dan,
You do have a float chamber problem, It can be as little as trash in a needle and seat or worn needle and seat or even a bad float. You should also check the venting of the float chambers to see that they are clear and are vented into the charcoal canister. You probably should check the fuel pressure to see that someone has not installed the wrong pump and thus too high pressure. It should be from 1.5 PSI to a max of 3 PSI. Anything higher will force the fuel past a good needle and seat.

You do not have to remove the carburetors to get to the floats etc. Just remove the fuel and vent lines and the three screws in each cover and lift it out on each carb. The float setting is 1/8" to 3/16" between the float and the top cover when the needle is closed.

Howard