One carb is spitting fuel - Alfa Romeo Bulletin Board & Forums

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post #1 of 18 (permalink) Old 02-25-2017, 11:54 AM Thread Starter
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One carb is spitting fuel

I rebuilt these Webers and the problem continues. The venturi closest to the firewall keeps spitting fuel. The carbs are rebuilt (took them apart, cleaned and replaced gaskets), the rubber mounts are new and that one half of the carb keeps spitting fuel. Any advice? If you look close, you can see the front three venturies are dry, the one close to the firewall has fuel leaking out. When I accelerate the car, it actually spits fuel out of the carb.
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post #2 of 18 (permalink) Old 02-25-2017, 12:39 PM
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Maybe a leak in the vacuum hose to the booster or in the booster diaphragm. Try removing the hose from the manifold and plugging the port.

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post #3 of 18 (permalink) Old 02-25-2017, 12:57 PM Thread Starter
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I don't have any vacuum hoses that I know of......?

Its a 67 duetto... I have no hoses to carbs other then fuel.... I think...

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post #4 of 18 (permalink) Old 02-25-2017, 01:21 PM
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Ok, no brake booster? one venturi flooding could be the cold start enrichment device. Gordon Raymond found two of mine to be stuck in the bores.

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post #5 of 18 (permalink) Old 02-25-2017, 02:04 PM
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Take a compression/leak down test just to eliminate the basic causes.
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post #6 of 18 (permalink) Old 02-25-2017, 03:01 PM
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"When I accelerate...it actually spits fuel out..."

What, in a stream? Like you might have installed the accelerator pump delivery tube facing the wrong way?

I can't remember if these have one flat face or two...maybe that's not possible to do.
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post #7 of 18 (permalink) Old 02-25-2017, 03:43 PM Thread Starter
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Quote:
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"When I accelerate...it actually spits fuel out..."

What, in a stream? Like you might have installed the accelerator pump delivery tube facing the wrong way?

I can't remember if these have one flat face or two...maybe that's not possible to do.
It is bad enough to think that I may have installed that one facing the wrong way.... Does anybody know if that is possible?
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post #8 of 18 (permalink) Old 02-25-2017, 03:44 PM
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Quote:
I can't remember if these have one flat face or two...maybe that's not possible to do.
The single flat prevents you from installing them backwards.
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Ed Prytherch
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post #9 of 18 (permalink) Old 02-25-2017, 03:46 PM Thread Starter
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Ok, no brake booster? one venturi flooding could be the cold start enrichment device. Gordon Raymond found two of mine to be stuck in the bores.
I'd like to look into this possibility, how can I check these "bores".
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post #10 of 18 (permalink) Old 02-25-2017, 03:53 PM Thread Starter
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The single flat prevents you from installing them backwards.
I think I figured out what these guys were, they can only go in one way and have two bores, one larger bore at the top and a very small bore toward the bottom. I cleaned these out and thankfully they cant be installed incorrectly.
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post #11 of 18 (permalink) Old 02-25-2017, 07:02 PM
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Quote:
I'd like to look into this possibility, how can I check these "bores".
The pistons slide in the vertical bores. A spring forces each one to the bottom and the cable operated cold start mechanism raises them to add fuel into the main bore of the Weber. The Weber manuals are posted on the internet. You should be able to find them with Google.
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Ed Prytherch
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post #12 of 18 (permalink) Old 02-26-2017, 01:19 PM
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Are all 4 fuel screws wound out by the same number of turns?
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post #13 of 18 (permalink) Old 02-26-2017, 01:53 PM
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My thought too.....

A complete rebuild includes aligning the butterflys. A slightly bent throttle shaft will cause one or more throats to allow more air thru than the others. Idle enrichment screws should be ABOUT the same number of turns when properly tuned......

Spitting back can be caused by a lean cylinder.....

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post #14 of 18 (permalink) Old 02-26-2017, 02:09 PM
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If it's leaking fuel is it possible that you have a faulty needle valve, assuming the floats are set correctly?
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post #15 of 18 (permalink) Old 02-26-2017, 06:26 PM Thread Starter
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Are all 4 fuel screws wound out by the same number of turns?
Yes, I am positive.
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