Weber 38/38 fuel leak advice

[boonies]

Looking for some advice on the issue below:

I have fuel visibly pouring out of the venturi on the choke side of my front carb (only on one side) when the engine is off of idle (at idle the issue doesn't occur). Meaning the throttle is increased slightly or even significantly, I can see the accelerator pump jets activate briefly, but separately fuel is continuously pouring out of the choke side venturi.

The back carb choke side looks slightly damp, but not the visible fuel pouring as seen in the front carb so that is likely just from the accelerator pump jet.

I have been adjusting (lowering) the float level without any improvement, but as I think more about doing that, I would think that there must be another issue as only one side of the carb is affected.

I did pull the choke side emulsion tube and air corrector, and both are clean. I am now thinking that it could be that the power valve is allowing too much fuel to be admitted, but why only on one side if that is the case?

 

[HB Chris]

On one of my zeniths one of the carbs had a very slight opening of the main throttle butterfly at idle which caused fuel to be sucked in from the bowl. I kept opening up the carb to check float and valve. The linkage was rubbing on the manifold causing it to be open.

 

[boonies]

Thanks Chris, that is interesting and I will take another look. I am fairly certain that my linkage is not touching anything as I was trying to use a smaller phenolic spacer, but had to go back to my larger spacer because of interference with the manifold when using the smaller spacer.

in my case I am causing the throttle plates to open as I run the RPM's up and that is when the fuel starts to pour through, but only on one side.

One thing I am going to try is to run up the RPM and cover my hand over the carb to create a high vacuum with the throttle plates open to see if that will suck through anything inside the carb circuits. Not likely this will work, but I think the next step may be to pull the carb again and open up all the jets and apply some compressed air to each of the jet seats (idle, main, power valve, air corrector) to dislodge anything that might be creating a blockage.

Keep the thoughts coming!

 

[Honolulu]

Assuming that "venturi" means the flared bit at the center of the throat, I had that on my '69 2500, never did solve it. At the time I suspected the carb float was not floating enough, or somehow the fuel level in that carb was too high, causing overflow via the venturi. That's mostly how carbs work, lower pressure sucks fuel through the venturi... but too much if the float bowl is overfilled.

IIRC there are other possibles including the carb upper and lower castings not being sealed, or a crack in one of them, or... idunno.