Weber Carb Gurus Wanted: "Bucking" Issue 38DGAS

[sp73]

I have this carb in my 1987 LandCruiser. It's about one year old; the truck runs GREAT except...

It will "buck" around 35-40mph occasionally. I believe it only happens after I add any quantity of gas. Letting off of throttle stops the issue, increasing throttle causes massive power loss. I can drive the truck for days and never experience this. Once fuel is put in the tank... there it is. Again, it is intermittent.

I have changed fuel filters and used dry gas type products. All ignition components are new. The shop that sells/installs the carbs thinks I need to re-jet it to one size smaller on the main jet and check the timing.

My thinking was water/trash in the tank getting tossed around with a refll but this has been going on for almost one year now.

Thoughts?

 

[wings&wheels]

I agree with you that the problem is most likely upstream of the carb and the tank trash theory is plausible, possibly getting stirred up when you add fuel. Generally carb problems are not intermittent, unless you have something in the fuel bowl but that is unlikely. That being said, have you cleaned both jets? My ICH on a Land Rover would get plugged after sitting for a month or so. What does the inside of your tank look like?

 

[spasm3]

Iirc there is a bolt on the side where the fuel inlet is. Under the bolt is a screen. I would check that for trash from the tank.
The spark plugs should tell you if you are jetted too rich.

 

[spasm3]

Pic of fuel inlet, if yours is like this.

 

[sp73]

Pic of fuel inlet, if yours is like this.

I agree with you that the problem is most likely upstream of the carb and the tank trash theory is plausible, possibly getting stirred up when you add fuel. Generally carb problems are not intermittent, unless you have something in the fuel bowl but that is unlikely. That being said, have you cleaned both jets? My ICH on a Land Rover would get plugged after sitting for a month or so. What does the inside of your tank look like?

Thank you. I have not cleaned the jets - - they are less than a year old and I use good quality fuel/the truck does not sit for more than about two weeks at a time. Can't rule them out though! I do not know what the inside of the tank looks like so when I have time I am going to drain it and put my boroscope up in there.

 

[Cujet]

Sounds like a fuel pressure gauge is in order. Followed by a roof mounted jerry jug and external low pressure fuel pump, apocalypse style