MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Fuel pouring from charcoal can

I have a real mistery.My 75 MGB is fitted with twin HIF SU carbs and suddenly this season when the weather is hot the motor will stop and gas will pour from the charcoal can dump valve.After things have cooled down the motor will restart and run just fine.I do not want to just block off the hose to the canister fearing that the gas will flood the motor. Any thoughts on this would be helpful. Thanks Bob
Robert Olivier

Bob,

I had a similar thing happen on my '74 a while back. Came home one night and got a strong smell of gas from under the hood. Fearing the worst, I found that there was fuel leaking out of my valve as well.

Long story short, I took my charcoal canister apart to have a look at the innards (I was told that this leakage could be a result of a blocked canister). Sure enough, the ingredients were far from perfect. Pretty much packed solid.

Luckily I had another canister that provided clean charcoal. Re-assembled it all and so far it's worked great.

Might be worth a look.

Cheers
Simon
Simon Austin

Float jets in the carbs are sticking. There should be no fuel in the canister it is for fuel vapor. When the floats rise as the carbs fill with gas there is a jet that closes, if there is dirt or they are worn out raw fuel leaks out the overflow tubes into the cannister.
John A

Bob, John has the correct answer to your problem. Clifton
Clifton Gordon

No mystery, as John says. Try disconnecting the fuel pump, running the carbs dry, then reconnecting the pump. This can be enough to shift a stray bit of dirt. If it happens again immediately maybe a float has punctured and sunk, or the valve is ridged. If it happens again shortly afterwards you may have dirty fuel from a corroding tank. You could try replacing or fitting a fuel filter as a short-term measure.
Paul Hunt

Thanks everyone for your quick replies.I will drain the carbs and change the fuel filter.The carbs have been rebuilt and the needles and seats have been replaced.I will let you know if the problem is solved.
Thanks again. Bob
Robert Olivier

Do these canisters need maintenance and if so what should it be?
Richard Stinchcomb

Bob, I just had the exact same problem with my '74 with HIF carbs. My problem was the rear carb's float had a leak and was almost filled with gas. The charcoal cannister was also filled with gasoline and would "spit" the gas to the ground via the dump valve when the engine was turned off. My float leak was in the float's seam. What I did was drill a small hole in the float to drain the gas and then plugged the hole and seam with JB Weld. It's been 2 weeks and all OK. Oh! I also dismantled the charcoal cannister and dumped the charcoal in a old "cookie" sheet and set the pan in the middle of the driveway...AWAY FROM EVERYTHING!!! Took a match and "CAREFULLY" stood back and "lit" the charcoal and let it burn itself out. The gas impregnated charcoal will ignite quickly and VIOLENTLY!!!! (as would be expected.....it's GASOLINE!), so if you choose to do this "cleansing method" (you're own your own), BE EXTREMELY CAREFUL!!! Some replace the charcoal with fish tank filter charcoal ...which is certainly a safer method. Good Luck, Buddy
Buddy N.

This thread was discussed on 08/07/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.