Need help with stumbling engine

[newschool]

I have a 350 with a 1406 carb. It often sits several days without being started. When I first got the truck it ran fine. I then replaced the rotted cab and fuel tank. Now things are a mess. It only runs correctly now when its between medium and heavy acceleration. Other wise it stumbles and has no power. It has never backfired through the carb or exhaust. What has me baffled is I drove it last week (30miles) to pickup some hay and it ran just fine. I drove it yesterday and its back to running like crap. I rebuilt the carb this morning and put it back on the truck and there is no difference. It looks like it has a newer fuel pump on it. I changed the fuel filter after I changed the fuel tank and then about 2 weeks after that. The fact that it ran great for one day is a mystery. Any sugestions on what could be the problem.

[shadetree]

This thread should really be in the engine & drivetrain forum, but I'll post my 2 cents worth. You mention changing fuel tanks, a strong possibility is a kinked rubber fuel line. That would fit your symptoms to a "T".

[newschool]

Thanks Shadetree. I checked the fuel lines and I couldn't find any place where the were pinched. I took both lines off at the fuel pump and blew air through them. The large line feeding the pump was fine but the return line is plugged some where within the sending unit. I'm guessing that's the problem.