Funky fuel system problems.. starving after 1/2 tank

[gintaras]

Morning update..
starts up cold no problem, has a nice, healthy idle until it warms up, and then the "shaky" idle starts up, at stoplights, etc... At WOT there is a "spitting" like a rapid misfire.. I am pretty convinced it is junk in the carb, how involved is the Qjet rebuild?

[joedoozer]

haysonj brings up a good point. Try an electric pump in place of the mechanical. If it does not solve the problem, that doesn't mean the pump is still good. You may have more than 1 problem. If electric pump doesnt fix it, try running a supply line from the E-pump into a 5 gallon jug. This would eliminate all the old lines, crud in the tank, rusted pick up tube, plugged filter sock.....and a list of other problems. That way you know you are starting with a good pump, good fuel and good lines. Problem still there, then it points to the carb. If the problem is gone, then it is from the pump back. Try different combinations of solutions. Eliminate just the tank, or just the lines to the tank.


On a side note.

I built a lot of Qjets when I was younger, too poor to buy a new one. Qjets are a complicated carb (compared to a Holley), but in this day and age finding some how to's on the web should be fairly easy. And I am sure their is a wealth of knowledge right here.

I had a similar problem with my truck. But it wasn't fuel level related. Not having a choke on my carb, I would richen and lean out idle mixture screws depending on the season. And when it got cold and I was to lazy to back the screw out a 1/2 or so, it would give me a shake at the stop lights, and a definite spitting almost "missing" at WOT. But it would clear up if I left my foot in it long enough.

Not saying its an idle mixture problem. Just my long winded way of saying I would look into the carb.

But it is wierd that it happens at 1/2 tank mark.

Is the truck at 1/2 tank when you started it, stated in your morning update?