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MG MGB Technical - Fuel Leaking through the Canister

I have a 74 1/2 CB Roadster that is leaking fuel through the canister. Most of the advice given previously have been to suggest that the carbs are stuck open.

So this is what I've done. I disconnected the fuel pump to see if the carbs would "unstick". well without the fuel pump, the car doesn't even turn over.

With the fuel pump feeding fuel, the car does start, but does not idle.

This being my first MG of any kind, I'm guessing that I have isolated the problem to the HIF4 Carbs. I noticed that Moss and Victoria British both sell rebuild kits. Are they all pretty much the same? Most importantly, which comes with idiot proof photos and simple directions???

Thanks for any help.
ChuckE

Chuck,
looking at the VB catalog it appears they are selling a very basic gasket kit with needle valves.
The Moss kits are more comprehensive. I assume each kit has a basic SU diagram but not a
detailed how to rebuild set of instructions. They will tell you how to make the basic adjustments.
You may want to consider ordering repair kits from The B Hive, they are not SU kits but I have
used them with good results. They cost around $22 each. They also have basic instructions
The web site for the B Hive is:
http://www.thebhive.com/index.html
If you have some specific problems while reworking your carbs post here and someone will
give you an answer. Clifton
Clifton Gordon

Is it coming from the carbs or the tank? Just on the off-chance, take the piping from carbs to cannister,and check.
Ken R
Ken Rich

Ken,

I'm not sure what you mean?
ChuckE

Before you order any carb kits, Chuck, try taking the handle of a screwdriver and rapping on the bottom of the HIF's. It might be nothing more than a stuck needle/valve seat. Sometimes wacking them a couple of times will free it up. If that doesn't work try taking the bottoms off the HIF's while they are still on the car. Once the bottom plates are off, the float will be hanging down. Try gently tapping them up and down with your finger to see if you can feel any fuel sloshing around in one of them. If you do, then you have a pin hole in one of the floats which causes it not to float up and shut the needle/seat off. Fuel keeps flowing into the carb and out the overflow, into the canister, and out the drain pipe from the canister.

It could also be if you have Gross-Jets that there is a piece of grit in one of them which will jam it open. This will also cause the fuel to keep flowing and into the overflow.

You might be able to use a mirror to determine this.

Robert
Robert Rushing

What I mean is, are the the fuel bowls overflowing to the canister, or does the flow come from the tank? If you take off the pipe from the carbs where it meets the canister,and turn on the ignition for a moment or two, you will see if the carbs are causing the fuel flow or if it is coming up from the tank via the evaporation system- I think that is how the system functions/malfunctions.
Ken R
Ken Rich

What Rich says is true. That's the first thing you should check before trying anything else.

Robert
Robert Rushing

This thread was discussed between 03/05/2002 and 04/05/2002

MG MGB Technical index

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