weber carb leaking fuel! Ideas?

[joehahn]

Hi fellas,
recently i have noticed that a trickle of gas comes out of the nut that attaches the throttle linkage to the throttle shaft on the right bank of carbs (it appears literally out of the center of that nut). Why would that happen there? It appears to only happen afer I have pushed the car pretty hard? Please let me know if you have any advice as I am uncomfortable having gas leak back there! Hopefully it is a quick fix.

Joe 68 L (2 liter 40 ida's)

[dhaines]

probably gas leaking onto the top of the butterfly and seeping between the shaft and the housing. You can have new bushings put into the housing but doubt it is worth it if the leaking is that little. The other suggestion is to pull the top off the carb and make sure the accelerator jets are tight. If you do that you might want to replace the gasket between the carb halves, as that could also be a source of gas leaking onto the butterfly. Anyway, my 2 cents worth....

[joehahn]

thanks doug! if i post pic of exploded view of carb can you tell me which "gasket" you are talking about? I know the gasket between the top half and bottom half but it doesn't appear to be that.

thanks,

joe

[911pcars]

Joe,
You shouldn't have any liquid fuel leaking in that area. The only source for significant fuel flow is from the main discharge nozzle. If this happens right after shut off, your carbs may be suffering from percolation in the float bowl(s). Heat from the engine increases fuel temp./air pressure in the bowl. This causes the expanding fuel to rise above the normal float level, then dribble out of the discharge tube. The engine may also be difficult to start or run roughly due to the excess fuel in the cylinder. Other possibilities are a high float level or perhaps excessive fuel pressure.

Remove the air filter housing and take a peek down the rear throat with a flashlight and mirror at idle and after engine shutoff. Idle fuel is normally delivered out of the small idle ports near the throttle plate. You may see fuel dripping from the main discharge nozzle (middle of secondary venturi).

The cure for this includes drilling some vent holes from the float bowl area into the air passage and installing insulator blocks under the carbs. PMO sells both solutions. Oh yes, change your oil too. The oil level may be up due to gas in the oil tank.

Hope this helps,
Sherwood Lee
http://members.rennlist.org/911pcars

[joehahn]

thank you mr. lee! it must have something to do with the heat as this is the first year that I finally just said screw it and drive in intense heat. i would deduce that that is the problem as it only happens when it is real hot (so far, i think). why do i change the oil though? is there (perhaps) a false middle reading on the stick right now? could be, i only put in a little over 8 quarts after last change (1 month ago).

Thanks,

Joe 68 L

[911pcars]

".....why do i change the oil though? is there (perhaps) a false middle reading on the stick right now? could be, i only put in a little over 8 quarts after last change (1 month ago)."

I may have been a little overcautious with the change oil recommendation. Too much raw (unburned) fuel in the cylinders will find its way down to the oil sump and dilute the oil. You may not have run the engine enough under those conditions to affect the oil.

But you can verify this. Is the oil level slightly higher now than when you last checked?

Sherwood Lee
http://members.rennlist.org/911pcars

[joehahn]

....hmmm, not higher but mid stick. when i account for the various leaks that i have it should be dropping but it is not. is this a problem. shall i change it to be sure? $24 in oil is not a lot to pay to be sure right???

["A"steve]

weber 32-36 leaks fuel into secondary venture . it appears it is syphoning thru the main jet in fuel bowl . any ideas greatly appreciated ... kzsteve@yahoo.com

[911pcars]

Originally Posted by "A"steve

weber 32-36 leaks fuel into secondary venture . it appears it is syphoning thru the main jet in fuel bowl . any ideas greatly appreciated ... kzsteve@yahoo.com

If the fuel level in the bowl is too high (float bowl adjustment), fuel will exit the sec. venturi discharge nozzle prematurely (before add'l fuel needed at off-idle/part throttle).

To confirm, remove air cleaner housing. With a flashlight and engine ON, look into each throat. While at idle, there should be NO indication of wet fuel above the almost closed throttle plate.

If so, obtain one or two PMO external float gauges to measure/monitor the fuel level with engine ON. Unless grossly out of adjustment, adding or subtracting fiber washers under the float needles (2 each carb) will modify the fuel level in their respective bowls.

If flooding occurs only after/during a hot soak, the fuel could be expanding due to excess heat. Research the PMO-fixture to drill bowl vents in the carb body. The fix also includes adding phenolic spacers under the carb to reduce heat transfer from the engine.

Sherwood

["A"steve]

thank you . ill try it & get back to you .... steve

["A"steve]

do they plastic floats ever saturate causing them to sink ?? ............ steve

[frankc]

Originally Posted by "A"steve

do they plastic floats ever saturate causing them to sink ?? ............ steve

I don't know about the PMOs, but the floats in my Webers are metal "balloons", so their buoyancy should never change unless they are damaged in some way.

["A"steve]

thanks again . the brass floats are like 10 yrs old weber told me . mine are composite .

["A"steve]

any other ideas greatly appreciated ............. steve

["A"steve]

ok , still need help on my weber . 32/36 manual choke . float does not seem to seal . the fuel fills manifold & motor . new float , needle/seat . need new ideas please ......... steve

["A"steve]

thanks for all your help ............ steve