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MG MGB Technical - Weber 45 DCOE

Hi,

Yesterday I discovered that I'm having a fuel leak on my DCOE carb.

After the engine has been shut off, fuel was leaking out on the SET SCREWS from Choke and aux venturi!

I'm afraid to tighten the screw to much, because there is a risk of deforming the venturi's

Has anyone an idea to fix it?

Thanks,

André
André

Hi Andre:

A drop of the milder loctite would seal them as well as be extra insurance so those screws won't loosen.

Unfortunately that means the raw fuel will drip into your cylinders instead. You might want to poke around to see if there's something else wrong that's causing the extra fuel to be present in the barrels. Could your float be leaking or the float valves stuck? Is your float height to high? Is your fuel pressure to high?

HTH!
Mike Polan

Hi Mike,

Since the carb is a Type 152, i can't find the exact float settings

I don't think the fuel pressure is to high, because i never before had this problem

The problem is only on one barrel

I will ckeck the jets and the float tonight

All ideas are welcome

Thanks,

André
André

I've got a 152 as well, and couldn't find any float level references for it either - what a pain. I was chasing an off idle hesitation and popping on underrun for ages. The tuning book I had said to leave the float level alone, while the tuning aid sheet that came with the carb had "low carb float level" as one of the causes of poor running - but no recommendation for a setting. I eliminated everything else on that sheet, trying all sorts of jet combinations till I decided it *had* to be the float level. I found one reference that suggested 5mm (Porter's MGB DIY Restoration Guide) but that resulted in a rough idle from raw fuel dripping down the barrels - I think it was for an older version. I fiddled a bit and finally settled on 10mm (the carb came new set at 12.5), which transformed the car - idles nice, no more bog or popping at all.

Sorry I can't help much more with the leaking problem. Odd that it's only from one barrel. Is it a stain or dripping? I'm guessing raw fuel must be dripping from somewhere, running down and between the carb body and the venturi, then out past the screws. Any chance it's just the cold weather - a bit too much enrichment or maybe even a "sneeze" back through the carbs that blew out some fuel?
Mike Polan

Mike,

I did some home work:

-I took of the air filter and ram tube, started the engine and looked with a torch and mirror in the throat: raw fuel is dripping out of the aux venturi nozzle, leaking in the carb body, and exactly as you said past the screws.
-the problem only happens when the engine is iddling
-when the main circuit is in, the mixture is not so bad (A/F meter on board

I did some testing with cutting out the fuel pump: it looks better, but it is difficult to disconnect the pump and in the meantime looking in the carb...

I checked the needle valve: some light scoring is vissible...

According to the pump spec (mitsuba electric pump)the max pressure is 0,3 bar, what is maybe a bit high for a weber. A check with a manometer would be good

So... i think that you are right: it must be very light flooding

The first step is to change the needle valve . If the problem still hapens i will check the fuel pressure.

Do you have a pressure regulator? set at what pressure?


Thanks,

Andr
André

Hi Andre - sounds like a good plan. Nothing fancy here - stock SU fuel pump with no regulator, worked fine for the last 10 years or so.
Mike Polan

(and I AM a member...:)

I'm a little late to the party, but I just overhauled the three (3) 45 DCOE type 152 carbs for my Austin-Healey this past weekend.

Mike: you are correct that the recommended float level is 12.5 mm. Mine too were set lower than this so I may have to go back into it and adjust them once the carbs are back on the car (waiting for Jet-Hot to return my headers now).

Andre': I am using a Holley fuel pressure regulator that I set up with a manometer (67.5" H2O = 2.5 psi). Don't waste your money on the cheaper regulators (around $30.00 US). Some of them just flat don't work at all! The Holley unit was >$60.00 (as a reference).

I think you're on the right track with the needle & seat. Fuel shouldn't be under pressure at the entrance to the auxiliary venturi, it should only be drawn out under a vacuum (as a result of the pressure drop through venturi).

I took some nice pictures of the various circuits in the carb, but unfortunately can't show them in this post. You can see them in this link though:

http://www.britishcarforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=1&t=001597

Good luck with yours!
Randy Forbes

This thread was discussed between 16/02/2004 and 18/02/2004

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