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Mon Feb 08, 2010 9:44 am

Installed a set of ICT on my 2.0L 78 bus while I get a set of IDF's together. They run great, no equalizer tube, feeding 2psi to the carbs. The problem is after about four hours after shut down the outside of the left carb starts getting wet with fuel, this is on the accerator pump side of the carb, and begins at the gasket for the top. First the gasket gets wet then fuel runs down the carb, down the manifold and I have a puddle on the top of the head by morning. I have replaced the needle valve twice, current one is a Weber, not an aftermarket. Replaced the float although the one I took out looked good and had no leaks. Set the floats to 8mm and also replaced the top gasket. Carb does not get hot when running, have a phenolic spacer between the carb and manifold. Only happens on the left carb, fuel line to both are just about the same length and approach at the same angle which is low, regulator and tee are lower than the base of the carbs so it is an uphill climp to the inlets. Even have a "U" in the fuel line off the pump that is higher than the top of the gas tank to eliminate gravity feed. When I pull the carb the entire back side of the carb is wet, both top and the two intake to carb gaskets are soaked, but no fuel down the inside of the manifold, the oil has no fuel in it, stuffed a paper towel down the intake and it comes out dry. The bowl is not flooded, apears to have the right volume of fuel in it. While driving around there are no leaks, do a little shopping and everything stays dry, it requires sitting for several hours for this leaking to begin. I have run out of ideas, clamped the fuel line last night, which seems to of stopped the problem, but that is not practicle for day to day use.

Ideas and input would really be appreciated.

Mon Feb 08, 2010 10:43 am

busman78 wrote: Even have a "U" in the fuel line off the pump that is higher than the top of the gas tank to eliminate gravity feed.

Your loop in the fuel line probably won't stop siphoning action if the line is full of fuel. For the gasket to be wet wouldn't the level in the bowl have to be up at the top? And when it's not running you wouldn't have over pressure problems. So it still sounds like float level is set to high or the float valve is leaking or a leak where it screws into the casting. Does it do it when there is less fuel in the tank? I don't know if your gas cap is vented but I'd see what happens with it loosened. Also maybe drop that "U" down to normal height to see what happens..

Mon Feb 08, 2010 11:07 am

I can swap tops from right to left, good idea, that way if the right carb starts leaking that points to a possible crack. The floats at 8mm is more than the standard 6.5mm. Not sure about the gas cap but the tank is vented.

Buses are notorious for gravity feeding fuel, with the height of the carbs barely above the level of the bottom of tank, the old water level device really becomes a reality. I can pull the fuel line off the exit part of the U and residual fuel will drain out but that is all, pull the in line off the input to the U and the tank will drain into the engine compartment.

Mon Feb 08, 2010 2:12 pm

I would maybe take the carb off and do a visual check for cracks. But I would think it is the accelerator pump gasket so I would just replace it for safety and to cross something off the list cause I have a friend who set his bug on fire because of a bad accel pump gasket lunkly we were in a shop working on it so we were able to put it out.

Mon Feb 08, 2010 2:47 pm

Yep, left that out from above, did the accerator gaskets, even dropped the idle to 825 to close the throttle more, bus wants around 950 due to the cam, in case the accerator or progression circuit was engaging. Since the wet starts above the accerator mount highly unlikely.

Just did what Desertbusman suggested, did a visual under a magnifier for any crack in the top, found none, so swapped the two tops, so if the leak shows up on the right side now I have some defect in the top. If it is still on the left then, I am back to square one. Noticed when I pulled the fuel lines off there was no fuel pressure against them.

Wed Feb 10, 2010 8:58 pm

Update, with the switched tops the same carb (left one) leaked, so I pulled out a spare ICT, cleaned, set it up and installed it. No leaks. Took the leaky carb, set it up on the bench and tried to force a leak by gravity feeding fuel and then by pressure. Hit it with 7psi and no leaks, no over running the float. That ICT must have some kind of personal problem with my bus.

Wed Feb 10, 2010 10:20 pm

If I understood your notes, you only swapped tops, correct?

webers are notorious for the tops warping when they are over tightened or with age. However the leak should be below the bowl fuel level. I might look to see if the accelerator pump gasket is slightly perforated or the fuel inlet barb is leaking where it is pressed into the housing.

Thu Feb 11, 2010 7:37 am

Yep did the tops and the same carb leaked, accerator gaskets were replaced on both days earlier, just to keep them matched, several needle valves and resetting the float level from 6.5mm to 8mm. A day of bench testing provided no indicators of where or why. But I am not done, even if I have to put the carb back on the engine.

I did not specifically check the inlet for how tight the brass nipple is, will do that today, thanks for the idea. Will also pull it apart and do some flat testing.