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MG TD TF 1500 - Carb Overflow

I don't want to restart a debate about tickler pins, overflow pipes and such, but I have a situation I need some advice to solve.

On two days, with a normal starting day in between, my rear carb has overflowed through both the tickler pin hole and the overflow pipe due to the fuel pump running on and on. I had a "to-do" to seal the tickler pins, but I failed to get to it soon enough.

I pulled the cover of the rear carb, and using Dave DuBois' article, and other archive information, found that the lever does not catch or prevent the needle valve from closing, nor does the float have any fuel or holes in it. The lever appears to operate normally opening and closing the valve, and the float "floats."

Any ideas of what to check next?

Thanks in advance

Larry
L Karpman

Larry,

Check to see if there is dirt on the seat of the needle valve or the needle itself, preventing it from closing properly. Clean the screen in the float bowl lid, and the fuel filter at the fuel pump.

warmly,
dave
Dave Braun

Thanks Dave. That's been done. I can see no reason why the lever would not raise all the way, or the needle would jam. No grit found anywhere. No abnormalities that I can see.

Cheers

larry
L Karpman

hello larry, perhaps i am reading your note incorrectly, but i read it as "...rear carb overflowed....due to the fuel pump running on and on..." i would offer that your pump is running because the fuel is leaking, not that the pump running is causing the leak. if you are CERTAIN the fuel is coming out the tickler and overflow pipe the only things i can think of are needle/seat, mechanical problem with the float arms/pivot point, cracked casting, or the float does not float. have you checked the float in boiling water? have you considered converting to grosse jets? best of luck. regards, tp
tom peterson

Yes Tom, the pump is running because the float did not cause the needle to shut off the flow, hence the leak. And yes, I saw fuel spurting/burbling from the rear carb tickler pin, and main flow was out of the rear carb overflow tube.

I have checked the float, and it does float in the fuel. I pulled it out, and there is no fuel inside. I checked the lever arm action and pin, and the needle valve. All seem to be fine and clear of any particulates. I am ordering Grose jets tomorrow. I too am puzzled.

Larry
L Karpman

Hi Larry: Forty years ago, when I was going to college, I had a Triumph TR-2 that had a similar problem. It turn out to be a small nick in the valve of the float chamber that prevented tha valve from closing. Carefully check the and see if it has any burr or nick. I am using Grosse valves in my TD and am very satisfied with them. I hope this helps.

Stuart

Stuart J. Ramos

Larry, what if you exchange the needle valves in front and rear carb and then check if the problem stays at the same carb or that it has moved with the needle valve. Good luck, Huib
Huib Bruijstens

Larry, I went through a similar thing. Every time the car would sit for a couple weeks the rear float would stick and the carb would overflow. I had an inline filter between the pump and carb at the time, so grit (usually the most likely suspect) was not the problem for me. All was checked per Dave D's help to no avail. I had several year old Grosse jet type valve in place. At restoration I replaced it with a new one and it has been fine ever since. Couldn't see a thing wrong with the one I took out, but something was wrong somewhere. George
George Butz

Larry - Another possibility is damaged threads in the lid that the needle valve screws into or a crack in the lid. I had that occur in a non SU carburetor in a Mazada pickup I has some years ago. Cheers - Dave
David DuBois

All was well this morning. No overflow. But, that doesn't mean tomorrow won't be different. I am ordering the Grose Jets today.

Thanks all

Larry

L Karpman

Dave: My lids do not have threads as you describe. The needle valve just fits up in there, and is prevented from falling out by the lever arm. What am I missing here????

Larry
L Karpman

Larry, the needle valve seat screws into the cap. The needle and seat are purchased as a set. See Item #6 in the carburetor section of a Moss catalog.
Bud Krueger

Thanks Bud. Shows what I know :-) That said, I would think that it would overflow all the time, not intermittently. In any case I'll find out when the Grose Jets are in.

Larry
L Karpman

This thread was discussed between 25/01/2009 and 26/01/2009

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