^ Gotta agree with Blake here. Other than the name on the tailgate, your truck has nothing in common with the stuff dealership mechanics are trained on. It is older than many of the mechanics! You'd be better off taking it to someone who is familiar with old vehicles and carburetors in general, and Webers in particular.
Blake mentioned a fuel filter. I had a clogged fuel filter on my J20 and it produced the exact same symptoms you are describing. Replacing the filter cured it. Get under the truck and look for extra fuel filters between the engine and the fuel tank. Replace them all. That's the cheapest, easiest, most likely fix. If that doesn't do it, you will have to start paying a mechanic for his time...or randomly replacing parts and hoping you stumble onto the fix, which is
not the recommended course of action!
I wrote up a couple of pretty significant articles that might help you. The first is on freshening up an old vehicle. This deals with eliminating many of the problems old cars and trucks develop from neglect and unsympathetic owners:
http://www.sv3power.com/?page_id=250
The second article walks you through the tuning process of a Weber 32/36 DGV carburetor, step by step:
http://www.sv3power.com/?page_id=371
Each of those articles is written in multiple parts, so read them all.
Read and follow the first article before messing with the carb. All other problems must be corrected before you adjust the carburetor - period.
'85 J20 Old Man Truck, bought @ 65K miles. Not great, but better than nothing at all.
High quality dumb stuff in the
intro thread and the
slow build thread
Prospect, FSJ Prissy Restoration Association
Bad Company, 360th Misfire Regiment, 161st Haiku Assault Division
Tech Tip: there is no apostrophe in Willys. The more you know...