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MG MGB Technical - Fuel Leak - on a new fuel sender unit. Return it?

I fitted a brand new tank and sender unit to my BGT at Christmas and have been suffering from a poor fuel consumption.

Due to the recent heat wave and the fact that the BGT has been at work in our workshop whilst I have been using my midget I have found the leak. There was a strong smell of petrol in the workshop (not good for my colleagues), as the car normally lives outside and I could not smell any petrol fumes. Upon investigation I have found that there is petrol seeping out of the rubber seal in the sender unit metal plate where the electrical feed is attached to it.

I presume after 7 months this should not have failed and therefore I can also presumably swap it for a replacement one. It was from Moss UK.

Has anyone else experienced the same problem?

regards

Andrew
1975 Jubilee BGT
Andrew McGee

Andrew. I am most familiar with the later model gas tanks having the combined filler tube and fuel level sending unit. I have replaced the earlier type units, but it has been many years ago. Due to some recent cleaning, I cannot find my Moss catalog to find which type of fuel tank was used with the 75 B.

With the late models, there is a rubber ring which goes between the gas tank and the sending unit with a metal ring against the outside of the sending unit, locking it into the fuel tank. However, this piece can also be assembled with the sending unit directly against the inside of the fuel tank fitting, the rubber piece on the outside of the sending unit and the lock ring holding everything together. I have seen it done and the system leaked fuel when it was improperly assembled.

Thus, the first thing I would do is make sure the tank and sending unit a properly assembled, the rubber gasket is in the correct position and the lock ring is tight. If there is still a leak, I would try to locate exactly were the leak is coming from and post that information. Seldom does it come from the sending unit itself. Improper gasket assembly and bad rubber hoses are far more common.

Les
Les Bengtson

Les

Thanks for your comments, the seal is assembled correctly as you rightly pointed out. The leak is actually coming from the small rubber grommet that the electrical sender (white plastic) is sealed with.

I thoroughly dried this off and then sprinkled some talcum powder on the area and whilst I know that petrol is capable of capilliary (spelling?) action, the powder was immediately wet around the white plastic bit and then turned wet running down from there.

Hope this describes it better.

Andrew.
Andrew McGee

On my MGA, I had a sending unit leak until I replaced the rubber seal with a cork seal. Going on 3 years now and the cork seal has held-up well.
M. D.

Andrew. You are correct. If it were the rubber gasket, it would leak from the bottom area of the flange the assembly fits into. On the example I have at hand, the plastic piece has some form of black gasket between the plastic piece and the metal of the assembly. The plastic piece is secured to the assembly by a crimp and cannot be removed to change out the black gasket. I would contact Moss and tell them of the problem and request they supply a replacement under warranty.

Les
Les Bengtson

Thanks Les for confirming my thoughts

I will call my friendly local Moss office tomorrow and see how I get on, will let you know.

Now the question is, how to quickly drain a full tank of fuel out of it with resorting to syphoning (petrol makes me vomit! - sorry too much information there).

regards

Andrew.
Andrew McGee

Andrew. Remove the fuel line from the hard line to the carbs. Attach a 6"/2 Meter length of rubber fuel hose. Insert the end of the hose into a container designed to store fuel. Remove the wires going to the input side of the coil. Turn the ignition switch to the run position. Drain the appropriate amount of fuel--i.e. most of the tank. Turn off the ignition switch and change fuel containers as necessary. Put the cap on the fuel container as the hose is removed to prevent vapors building up and spillage.

When the necessary amount of fuel is drained,turn off the igition switch, and reattach the original flex line from the hard line to the carbs. Reattach the wires going to the coil. Check to make sure everything is again hooked up correctly and that the connections are tight.

Been there myself. Les
Les Bengtson

Andrew
I had the same thing 3 months ago when replacing my fuel tank and sender unit. Sender unit was leaking fuel from the small rubber O ring around the plasic base of the electical contact in the middle of the sender unit. I bought it from the MGHive. They said that they had had 3 returned with a similar problem and advised sealing with Araldite! I sent it back and got replacement from the MGOC which has not leaked.
Nick
N Argyrou

This thread was discussed between 10/07/2006 and 11/07/2006

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