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MG MG Y Type - Big Fuel Leak

Today I took YT 2659 out for a little ride. When I got home, I could smell fuel. I open the bonnet and fuel was pouring out of over flow tube of the float bowl. What do I need to repair this?
J Spears

Hi Jim

Take the float out of the float chamber - it is the brass thing in there and give it a shake. If there is fluid in there it is gasolene. Modern gas attacks the solder on the joints of the brass and gas leaks in displacing the air so the float no longer floats and actually becomes a stone and sinks. This causes the float chamber cut off not to cut off and gas continues to pour in until it overflows ... then it flows out!

If the float has gas in it, throw it away and get on to either Abingdon Spares LLC or Moss Motors and get an UNSINKABLE (yes I know they said that about the Titanic too) FLOAT for an MG TD. That will work fine.

If the float is actually floating and not sinking - that is it is actually on top of the gas in the float chamber, then check to see if the forks are in place. I have known them work loose when the incorrect cross pin is used and fall out. They could also be bent out of shape if they are in place and so are not providing the correct thrust on the needle valve. See the relevant section (FUEL SYSTEMS I think it is from memory) in the Workshop manual - there are very detailed notes in there about setting the height of the forks.

Finally, if all of that is in place and good, slip the cross pin out and carefully remove the forks and tip the needle valve out. Examine the top of the needle valve for seat wear on the pointy bit. If you can see a ridge, replace both the needle valve and the seat. Again MG TD is your croos-part at Abingdon Spares or Moss. When removing the old brass seat, and fitting the new one, use a deep wall socket and dont reef on it - it should be a firm snug fit. Over tightenting may not only strip the threads but could break the top of the float chamber.

Since you have the fuel line banjo off at this time, take a look at the two copper washers and make sure that they are not totally wasted and grooved but are nice and smooth. If you had a gasket under the lid of the float chamber (and you should) ensure that it is not twisted or pinched on refitting. If it is ... replace it too.

Paul
Paul Barrow

Paul,

I took out the float, and it was dry inside. The only rattle I heard was a piece of solder inside. The forks and the needle look fine. I put it all back together and was not leaking through the overflow tube. It looks like I need to replace the rubber gasket that seals the lid.

Could a piece of debris in the fuel cause the float to get stuck?
J Spears

Hi Jim

Yes it could so remove the forks and the needle valve (not the seat) and blow it out with some compressed air.

Paul
Paul Barrow

Hi Paul,

Yesterday I had the same problem with the other carburetor. It was running out of the over flow. I just had the fuel tank replaced, There may still be "grit" in the fuel lines. I remove and clean the fuel filter from the fuel pump. I could not believe all the debris that was in there. The car was running a lot better after that. Would it be wise to put another fuel filter in the system? I read some where that you always want to put it on the back side of the fuel pump, to keep the fuel pump from pumping fluids.

Thanks,

Jim
J Spears

They can go either before or after, if before then clearly you wont plug up the filters in the pump. I have seen in line ones mounted under the car against the chassis rails before now and provided you have easy access this is a good place for them as the do not distroy the period appearance of the engine bay.

Paul
Paul Barrow

This thread was discussed between 22/03/2012 and 01/04/2012

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