Gas leak from charcoal canister intake hose!

Hello

I have a 1972 MGB that I recently took the carbs off to clean and and did a few other maintenance tasks such as setting the valve spacing, setting the points on the distributor and changing the fuel filter. Now when I crank the car, it runs but at low rpm (1000-1500) it runs very rough and shuts off after a while. It seems to misfiring but when I pull off the spark plugs one by one the motor runs much poorly each time I take one off until I replace it. When I try to drive it I have little power. When I rev it up to about 2000 or higher it seems to be quite smooth.

My problem is: When I adjust the mixture and it seems as if it is right, after about 2 minutes of idle at around 1000-1200 rpm it shuts off and pours gas out of the bottom hose on the charcoal canister. If it idles for a minute or so and I try to hit the gas it seems to want to shut off. My first thoughts would be that I am flooding the engine but if I lean it out I have to keep the rpms around 2000 to keep it from shutting off. I read some other postings and check out some videos on you tube and tried all of the scenarios I could find to no success. I have not rebuilt or replaced the canister. I have checked the vacuum lines and the fuel lines under the hood, which are all fine but not the ones to the back of the car. (I can see through the filter it is getting plenty of fuel.) I did a static timing at 10 degrees. It ran ok before I did all this but now I can not seem to get it right again. Oh yeah, I fixed an exhaust leak at the bottom of the manifold where it meets the downpipes and changed the original air filter system to a pancake style prior to taking off the carbs but after it was running correctly. Any help is much appreciated.

Thanks
John

One or both of the seat/needles in the SUs are sticking or possibly the fuel pump is putting out too much pressure. What SUs do you you have...?

Also sounds like you could have a stuck float in one of the carbs. The overflow tubing goes directly into the charcoal canister - good thing, too, because otherwise the overflow might end up on the exhaust manifold. That'd be pretty at night - from a safe distance - but car-b-cue's can be expensive.

Turn the ignition to the "on" position but do not start the car. Odds are you'll hear the fuel pump constantly clicking, without stopping. It should stop once the float bowls are filled up.

Check James' idea also - definitely a likely culprit.

HIF. I had planned on rebuilding them soon. Now seems like the time. Thanks for your reply.

The fuel pump clicks between one and three times and then no more.

About the carbs: I have a pair of the HS4s as well as the HIFs which are currently on the car. I have heard that the HS4s might be a better carb. If I am going to rebuild a set I want to put the better set on. Any thoughts?

Not filmier with HIFs but I have heard they where supposed to be powerful SUs carburetors.

Could the new fuel filter flow more freely and hence cause the problem? It is a billet filter with s plastic screen filter element instead of the paper filter element.

My '74 with HIFs did the same thing until I gave up. When I pulled the carbs off, one float was full of fuel, the other only half full. And they were a bit dirty inside those chambers. A float problem is easier to remedy on HS4s!

Thanks for the replys. I just ordered the Master Rebuild Kit from Moss and the 2 Needles required as well. I am going to rebuild the HIFs since that is what is already on the car. Any other suggestions are greatly appreciated and I will report back in a week or so when I get the carbs rebuilt. Thanks. Any pointers on rebuilding the HIFs is appreciated as well. I am sure there are other threads on that though.

Have a good one.
John

If you are going to do them yourself, and no reason why not, then order the carb video from Moss. It is very educational as well as a good teaching video on rebuilding SUs.

Had the same problem only with a Stromberg carb turned out to be crap in the needle valve. Gas just kept flowing into canister, cleaned needle valve and all was well

Glenn

Your carb is definitely floading. Changing the fuel filter may have loosened some crud and it got into the float valve. Take a can of carb cleaner and shoot it in the fuel port on the carb. I'd let the engine dry out before starting again though to keep from a fire.