[T3] Weber Carb update

[Jim Adney]

On 14 Jul 2012 at 12:01, James Lingenfelter wrote:

> The fittings in  the carbs are NOT loose, the fuel hoses are simply
> loose on the  fittings, and no amount of tightening (or overtightening
> for that  matter) of the hose clamps will secure them. I still have
> fuel  seeping through at the connections. I just replaced these fuel
> lines  a few months ago with the highest quality hose I could get. The
> fittings on the carbs are the type that have one rounded "barb" at 
> the end of the fitting.

You may need to check what diameter of the hose you are buying. Yours 
is either too large or it was old and hard when you bought it. New 
resilient hose should seal without clamps on a nipple like that. At 
this low pressure, the clamp only serves to keep the hose from 
falling off.

> Also, still related to the Weber carbs: The last couple of times I've  
> had it running in the garage, within just a few minutes of running, a  
> lot of moisture is forming around the driver side carb, mostly near  
> the base it appears. When I first saw this, I thought I had a fuel  
> leak somewhere, but it is apparently water.... quite a bit of it....  
> enough to be running down the intake manifold after 5 minutes of  
> running. What could this mean? Is something happening to cause a lot  
> of condensation to form on the outside of that one carb?

Yes, the air passing thru the Venturi is expanding and the gas is 
vaporizing, both of which cause cooling. I'm guessing that it's humid 
where you are, and the cooling is causing the carb to cool down below 
the dew point. If you looked down the throat of the carb, you'd 
probably see the same thing happening on the inside.

In extreme cases, the condensed water will freeze. When it happens 
inside the Venturi, it constricts airflow and slowly reduces engine 
power. This is known as carburetor icing and is something that 
aircraft have to be very careful of.  


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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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