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MG MGB Technical - Fuel leaking from Charcoal cannister

HELP! I have a 76 MGB that I love. just purchased and has been running like a dream, albeit minimal speed. Hadnt started it for a few days, noticed fuel running from carb screw when it started. tightened screw/pin now fuel runs (and I mean runs) from Anti Run on Valve hose. If I remove the hose that runs from the carb to the charcoal canister, it comes from there. Fuel pump ticks away spewing gas from this hose, that I understand is NOT to have fuel in it!!
Why is this happening, and do I have to replace the charcoal canister, or can I just replace the charcoal??? See, I need Help!
Carolyn
C M Dobbs

Check your carburetors for an over flow from the float chamber (needle valves not shutting off). Cheers - Dave
David DuBois

Thanks, Im learning so much about this, now I have to take the plunge and take carb apart.
C M Dobbs

Carolyn - Pull the overflow hose from both carburetors to see which one is the culprit before you dismantle the carbs - the HIF carbs have to be removed in order to get to the float chamber. Also, once you find which carb is overflowing, tap bottom portion of the carburetor with a screwdriver handle. This may clear the stuck needle valve and eliminate the need to dig into the carburetor - at least until the problem occurs again. Cheers - Dave
David DuBois

Hi Carolyn, I had a similar problem and took the carb and float apart to get to the needle, which I blew out and cleaned, only to reassemble and have the same problem! Took everything apart again and this time unscrewed the brass housing that holds the needle and held it up to the light. There was a small piece of rubber jammed in the hole which stopped the needle from fully sealing against the brass seat, it probably came from cutting new petrol tubes on rebuild months earlier. The brass housing looked find the first time of stripping down, only when undone and held up to the light did I see the problem and then it needed a poke from a needle to get rid of it. Hope this helps and good luck. Pete
Pete Dyble

Thank you so much everyone. My next question is do I need to get a new charcoal canister, or can I remove charcoal and replace? Or just leave it alone?
Thanks Again.
C M Dobbs

You can reclaim the charcoal canister by
removing it from the car,
opening it and pouting the charcoal onto a flameproof surface such as a metal pan
igniting it wioth a torch to burn off the gasoline which has soaked it. When the flames die out, the fumes and gas are gone.
Re-assemble the canister ( I ended uip with some left over charcoal)
Re install in car

Search these archoves. I think th eprocess is desctibed somewhere in here. Yoy can also buy new "activated" charcoal ar a pet store; it's used in aquarium filters.
Dan Hiltz

Carolyn-
Over time both the filters and their enclosed activated charcoal degrades into fine particles to the point that fine particles of it can be drawn into the crankcase. One of the things that you do not want inside of your crankcase is fine particles of charcoal. Fortunately, rebuilding the adsorption canister is not difficult. The bottom unscrews in order to expose a retainer ring. The retainer ring is the piece that looks like a wheel that has three spokes. Notice that the retainer ring has six tabs in it that fit into matching slots in the bottom of the adsorption canister. These have to be very carefully depressed in order for the retainer ring to be released. After the retainer ring has been removed, you will find a filter element that is made of plastic gauze. Remove it, and then carefully examine it. If it is in decent condition, then set it aside for re-use. Underneath of the plastic gauze filter element you will find the old activated charcoal. It has the appearance of black pellets. These should be discarded. Under the activated charcoal, you will find another plastic gauze filter element like the first one, and a steel mesh screen. If the steel mesh screen is intact, save it for re-use. Next, you will find a special washer and a spring. These should be cleaned for re-use. Should the two plastic gauze filter elements appear to not be serviceable, you can make replacements from filter paper by cutting it into 3 1/2" (89mm) circles. Lacking this, you can use plain old coffee filters. Look around for some large enough to cut the discs from without leaving any holes. For replacement activated charcoal, use common aquarium filter activated charcoal that is available from any store that sells aquarium supplies. You will need about eight ounces of activated charcoal. Rinse it with pain water in order to remove any stray fine particles, and then dry it inside of an oven. When you are ready to reassemble your adsorption canister, place the spring and the special washer into position inside of the bottom of the adsorption canister. Next, install the steel mesh, and then place either your old plastic gauze filter element or your new, homemade paper filter on its top. After that, put in about eight ounces of the new activated charcoal, and then gently shake it down in order to settle it. It should fill the adsorption canister up to the point where the other filter and retaining ring will just fit into place. It you overfill by a small amount, it will not matter as the spring will compress enough to keep pressure on the activated charcoal. Note that it is necessary for the entire packed bed of activated charcoal to be held firmly in place by the spring so that internal friction will not produce fine particles that can foul the filter. Place the second filter element on top of the activated charcoal, and then place the retainer ring on top of it. Be sure that the retainer ring locks into place with its six tabs in their corresponding slots. Next, screw the bottom of the adsorption canister back into place, reinstall the adsorption canister into your car, and then reinstall the hoses. The center port on the top of the adsorption canister is for the purge line hose (flexible pipe) that goes to the rocker arm cover, while the port on the front of the top of the adsorption canister is for the vapor hose (flexible pipe) that attaches to a Y connection to the two vapor hoses (flexible pipes) which are attached to the overflow vents on the float bowls of the carburetors, and the port on the rear of the top of the adsorption canister is for the vapor hose (flexible pipe) that comes from the expansion chamber for the fuel tank. The port on the bottom of the adsorption canister is for the air vent line hose (flexible pipe). Note that heater hose (flexible pipe) material does not work well in these applications. In addition, avoid plastic hose (flexible pipe) as it has a tendency to harden and crack. Instead, go to a good auto parts store, such as NAPA rather than a discount parts stores, and tell them that you need an emissions-quality hose (flexible pipe) for both the hose that connects the center port of the adsorption canister to the rocker arm cover and also for the hose from the front cover of the tappet chest to the fuel induction system. This hose (flexible pipe) is also known to some vendors as “oil resistant” hose (flexible pipe) and, like fuel line hose (flexible pipe), is engineered to withstand the presence of both oil and fuel, as well as their vapors. The smaller hoses (pipes), both on the adsorption canister and the vapor separator, can be made from Original Equipment fuel line hose (flexible pipe) with no problems.
Stephen Strange

Carolyn,
I don't know if I'm too late with this but even so if you don't know about the John Twist videos it's worth it

the fabulous John Twist and video 186 Charcoal Adsorption Canister - MGB & Midget - http://www.youtube.com/watch?v=6qmLp-cJeCk
Nigel Atkins

This thread was discussed between 18/08/2013 and 19/08/2013

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