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MG MGB Technical - An occasional gas smell while driving?

Hello All,
I have an occasional smell (sometimes strong) of gasoline while driving my '72 B.

*rebuilt HIF's including solid throttle plates and new shafts, but noticed it even before then.

*The carbs are adjusted correctly (not too rich).

*I've been over the car from one end to the other but cannot find any leak evidenced.

*Still have all of the vapor canister lines connected.

*Vapor tank attached in trunk.

*new gas tank, fuel pump, sending unit.

Any ideas or suggestions? Does the vapor canister charcoal ever need replacing?

Regards, David
David Steverson

David; Some people do change the charcoal in the canister, I doubt if that would solve a fuel smell problem. Do you know if your new tank has a capacity limiting tank inside, see page 91 in the Haynes manual? If it doesn't the problem should go away after the tank fuel level goes down. When the smell is bad it may be a good idea to try checkiong to see if fuel is coming out of the canister. You mention a new fuel pump, SU? If not too much pressure could cause the problem. Maybe you have already checked all these items.

Clifton Gordon

The original lines to and from the canister (in the right rear fender are covered with braided steel. I find these original lines in most of the MGs I've looked at. Of course we cannot observe the condition of the rubber hoses underneath and I would suspect they are deteriorated and leaking fumes. I've tried to replace these and was sent hoses that did not have the correct fittings so I couldn't use them. I'll leave the name of the supplier out because frankly I can't remember.

Allen Bachelder

Mexican food.

rick ingram

How occasional, and under what circumstances? Full tank? Only going up hills or down? That sort of thing.
Paul Hunt 2

Good one Rick!

Clifton, the fuel pump is an SU.

Paul, I've not noticed a common factor as of yet. Wednesday for example on the way home from work, I noticed it while driving about 45 mph in light traffic, I may have gone around a curve about that time (can't remember). The tank was about 1/4 full.

I'll try and take more note of conditions when I smell it next.

Thanks for the input, Dave
David Steverson

Fuel tanks begin to corrode at the upper front from splash. Reach up there with a rag and see what you find.

Dan Robinson

Iook at the rubber tube at the fuelfiller neck in the boot, after years its rots out. Same at the 78 mgb i own.

Actually I forgot about the MGB olfactory fuel gauge - installed at the olfactory in Abingdon, of course. It works this way: if you smell gasoline, that means you have some.

Allen Bachelder

A tank with the top rotted out is usually visible by having staining down the sides, when dry (from either petrol or water!).
Paul Hunt 2

David, something you might check is the correct operation of the PCV system. If the orifice in the rocker cover spigot is plugged fumes can back up in the charcoal canister and escape.

Jim Blackwood

This thread was discussed between 05/01/2007 and 06/01/2007

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