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> Fuel Percolating in Carb....
MikeM
post May 23 2019, 06:28 PM
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Hi all...my friend and I are both having the same problem with fuel boiling or percolating in the carbs after shut down. It drips out of the carbs and onto the intake manifold. It's not much but it's dangerous and smells terrible. We both have Weber 44's and we are using the thick spacers between the heads and intakes. I have ordered the thick spacers for under the carbs also. Is there anything else to consider with this problem?
It wasn't even hot today and oil temps only about 200 degrees!!
Any and all suggestions appreciated!!
Mike
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Chi-town
post May 23 2019, 06:35 PM
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How are your fuel lines run?
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MikeM
post May 23 2019, 06:41 PM
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QUOTE(Chi-town @ May 23 2019, 06:35 PM) *

How are your fuel lines run?

I think just the usual way,rotary pump at the back. I dion't think there is a return.
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rhodyguy
post May 24 2019, 08:52 AM
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Fuel is dribbling on the outside of the carbs? Both of them? Can you see it upon shut down? Is fuel puddling on the throttle plates? Stock 44s? I'd be worried about fuel contaminating the oil.

Does fuel pour from the pump jet? Item #16, p50 of the CB Weber manual.
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MikeM
post May 24 2019, 09:50 AM
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I would not say it's dribbling out, a few drops is more accurate. Yes, you can see fuel on top of the throttle plates 10 to 15 minutes after shut down.
Hard to tell where it's coming out!!
Mike
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brant
post May 24 2019, 10:26 AM
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adding a return circuit can be a big help with this

I hate seeing all of the advice on the internet saying that a return line is unnecessary.

the fuel in the bowl still gets hot
but at least the fuel sitting above the motor inside of a fuel line isn't absorbing radiant heat... at least it is moving around and relatively cool when it enters the bowl.

b
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injunmort
post May 24 2019, 12:34 PM
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do you have insulating blocs between the heads and intake maifolds?
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MikeM
post May 24 2019, 03:15 PM
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Yes, I'm using the spacers between the heads and the intake. Just ordered the ones between the intake and carbs.
Thanks
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porschetub
post May 24 2019, 04:51 PM
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QUOTE(MikeM @ May 25 2019, 09:15 AM) *

Yes, I'm using the spacers between the heads and the intake. Just ordered the ones between the intake and carbs.
Thanks


Where is the pump located ? not in a hot area ?,you can't have any raw fuel in the carb throats as this fuel isn't atomized ,have you got a regulated fuel pump? if not this may be your issue,the float valves get over pressure and simply don't seal when they should be closed.
The fact you have fuel on the outside of the carbs is a worry,how your fuel is getting so hot is a bit odd as the spacer blocks are designed to stop heatsoak from the heads to the inlet manifolds that's why Porsche used them on the stock FI motor.
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rhodyguy
post May 24 2019, 06:47 PM
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With the pump energized, not started, can you see fuel entering a Venturi on the offending carb? Does only 1 carb have the fuel mess?
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MikeM
post May 24 2019, 07:44 PM
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No...you can only see fuel after about 15 minutes after shutting down the hot engine!!
Happens on both sides...
Mike
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