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MG MGB Technical - Petrol leak from absorption cannister

Had the ignition on,72 MGB, last night, engine not running, when i noticed the petrol pump kept ticking. found a puddle of petrol under the car near the starter and found it was coming from the rubber pipe that goes from the absorption cannister and stops just down by the starter motor. Now i haven't touched the carbs or altered anything in the fuel line/system for months, oh and no leaks under the carbs either.
Help please
Gerry

Gerry. Your carb overflow vents are connected to the charcoal cannister. Something is causing the carbs to overflow, the fuel pump is not shutting off because it keeps pumping fuel, and the fuel is being routed to the charcoal cannister.

You need to find out what the carb problem is--bad needle valve, bad float, crud not allowing the float to close the needle valve correctly, then correct the problem.

After the problem is corrected, the charcoal cannister needs to be removed and either rebuilt or replaced. Rebuild instructions are in the archives, in significant detail.

Basic process is to open up the cannister, dump out the old charcoal and filter, dry or replace the charcoal and filter, as necessary, and reassemble. Activated charcoal and the fiberglass filter, used in fish aquariums and available at pet stores, is what you need to rebuild the cannister, assuming the body is in good condition. All I have examined have been in good condition.

Les
Les Bengtson

Thanks Les.
come to think about it i did add oil to the dash pots just over a week ago, never leaked, well came out the pipe before that. The car has just been in/out the garage a couple of times after that( car not on the road yet). Do you think this might have some way affected things ?
Gerry

Just adding oil to the dampers won't have caused that. Not having used the car properly for a while (as seems to be the case) could well be the cause of fuel going sticky on the float valves.

The pump shouldn't click more than once every 30 secs with the ignition on and the engine stopped. More than that indicates either a leak at the float valves, or at the non-return valves in the pump. Disconnect the coil when doing this to prevent it overheating.

Disconnect the fuel pump (white from the main harness to the rear harness by the fusebox) and run the engine until the float chambers empty and the engine stops. Reconnect the fuel pump and turn on the ignition and the pump should chatter like billy-oh. If it is debris then the resulting rush of fuel though the now wide-open float valves may be enough to clear it, or even flush stickyness off the valves. But if not then you will have to investigate further. Remove the lid of the float chamber and look inside. If there is debris in the bottom - there shouldn't be anything more than staining, particles is definitely dirty fuel. If you have a fuel filter then change it, but the tank and lines may need flushing out if it is bad, and if the tank is corroding internally it may need replacing. I've heard of people pouring something in the tank and swishing it round to seal it, but it can also seal up the holes in the pickup and cause fuel starvation. Check the floats don't contain any fuel, and if not that or dirt replace the float valves.

Paul Hunt 2

This thread was discussed between 26/03/2008 and 27/03/2008

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