Calling all Weber experts......Help!

[Krustybus]

I've got a pair of 48 idf's on a fresh 1905, mechanical fuel pump. It runs great but leaks fuel down the #3 barrel (other carb is fine). It seems like it siphons fuel through the accelerator pump. This only happens after its shut down. There is a gurgling sound followed by a stream of fuel out of the nozzle, then more gurgling, more fuel.
I've rebuilt it twice ( soaked in cleaner, compressed air, fresh parts, correct float setting). I even sealed the pressed in plugs in the carb body. The problem continues. Anyone heard of this?
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Tim

[mharney]

What are your float levels set to?

Does your engine run hot? Does your engine compartment get enough cooling air?

Sound like to me the float level could be too high, and maybe your engine is conducting a lot of heat and causing the float bowl pressure to rise as the fuel is heated. Do your float bowls feel warm to the touch?

Needle and seat could be dirty too.

Fuel pump could be getting hot too when it sits there with fuel in it, maybe it's forcing fuel through too. You could test that by disconnecting the fuel line from the pump right after turning it off (in a well ventilated area of course), and see if the carb symptom stops. If it doesn't you know the fuel pump is not the contributor. If it is the fuel pump it may gurgle and spew some fuel.

[Krustybus]

Float set to 11. Fresh needle/seat ( 3rd set). Engine is pretty cool. No decklid on bus yet. Problem will happen even after 1 trip around the block.
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Tim

[mharney]

Have you checked the fuel pressure?

[Krustybus]

I haven't checked the pressure yet. May have to invest in a guage. I figured a stock mechanical pump wouldn't make excessive pressure. Also the leak is in 1 barrel only. Shouldn't there be problems elsewhere with high pressure?
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Tim

[mharney]

Maybe, maybe not. One needle and seat is going to be slightly more prone to leaking before the other one.. and one accelerator pump may be more prone to pass fuel than the other.. Weakest link theory I guess.

From the gurgling, the only thing I can think is pressure.

[rterfert]

Swap the carbs to the other side of the motor and see if the problem contiues or switches sides??
Sounds like a high presure problem though.

[Krustybus]

I'll try swapping them. I'll get a guage also. What should the fuel pressure be? If it's too high, who makes a regulator? Where in the fuel lines does it go?

Sorry for all the questions, but I'm dying to get some miles on this motor before the snow flys.
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Tim

[mharney]

Gauge should read about 3.0-3.5 psi

Regulator right before carbs.

[[email protected]]

you do NOT use a regulator with a stock pump. You raise the pump to drop the pressure. This is a common problem, because many aftermarket pump spacers are TOO SHORT, which kicks the pressure to the moon. I have seen over 10psi from a stock pump. You must check it and set it to 3-3.5psi if you want to tune the webers.

Fuel pressure is even more critical with Solex/Kadrons, which operate best at 1.5-2psi.

John
Aircooled.Net Inc.

[Turin39789]

[clearsurf2001]

Fuel pump base gaskets ... from John.
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Get ready for the injection