Rochester 2G carburetor idle mixture screws are unresponsive

I have a 1971 CJ5, 225 Buick V6 with a stock Rochester 2G carburetor. I am having trouble with the carburetor running rich to the point where the idle mixture screws are unresponsive. they can be completely screwed in with no effect on the idle whatsoever. The engine idles with them completely closed, and when the engine is revved, black smoke is emitted from the tail pipe. The carburetor is new, and the float is set correctly.

I'm thinking that there may be too much pressure from the fuel pump, and an excessive amount of fuel is being forced into the carburetor. The Jeep has 2 gas tanks, one under the driver's seat, and the factory tank in the rear. Years ago I removed the fuel return line from the rear tank (there was no return line to the under seat tank), and plugged it at the fuel pump, because whenever I used the front tank the fuel would just be pumped to the rear tank. I'm thinking that it may have been a mistake, as removal of the pressure relief of the return line may have excessively increased the fuel pump pressure. Could this be the problem?

If this is the problem, does anyone have a part number for a fuel pump with no return line that would fit the V6? I'm assuming that a pump with no return line would produce less pressure. Or, is it possible to install a pressure control valve between the pump and the carburetor that I could adjust to decrease the pressure? If so, where might I get one?

If this is not the problem, what else could cause the idle mixture screws to be unresponsive, and the carburetor to run so rich?

 

I found this pump with no return line at Rock Auto for a 1964 Buick Skylark 225 V6. Does anyone know if it will fit my 71 CJ5?

http://www.rockauto.com/catalog/moreinfo.php?pk=58770&cc=1319486

 

Before you start throwing parts at it you need to determine if it is actually producing too much pressure.
I've seen it happen, but rarely. More likely there's a problem with the carb itself.

 

10-4, I sent the new carb back for an exchange. I'm just trying to do some more research, because this happened on another carb that I had on the Jeep, but it was only 1 idle mixture screw that was unresponsive.

I don't know if the Buick skylark pump would make any difference. The specas are alomost the same<

Jeep (with return line):

[TABLE="class: moreinfotable, width: 100%"]
[TR]
[TD]Gasket Included[/TD]
[TD]Y[/TD]
[/TR]
[TR]
[TD]Inlet Count[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Inlet Type[/TD]
[TD]Threaded[/TD]
[/TR]
[TR]
[TD]Item Grade[/TD]
[TD]Standard Replacement[/TD]
[/TR]
[TR]
[TD]Maximum Pressure Rate (psi)[/TD]
[TD]5.75[/TD]
[/TR]
[TR]
[TD]Minimum Free Flow Rate (gph)[/TD]
[TD]40 GPH @ 1800 RPM[/TD]
[/TR]
[TR]
[TD]Minimum Pressure Rate (psi)[/TD]
[TD]4.25[/TD]
[/TR]
[TR]
[TD]Outlet Count[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Outlet Size[/TD]
[TD]1/2-20 UNF-2B I.F.[/TD]
[/TR]
[TR]
[TD]Outlet Type[/TD]
[TD]Threaded[/TD]
[/TR]
[/TABLE]

Buick (no return line):

[TABLE="class: moreinfotable, width: 100%"]
[TR]
[TD]Gasket Included[/TD]
[TD]Y[/TD]
[/TR]
[TR]
[TD]Inlet Count[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Inlet Type[/TD]
[TD]Threaded[/TD]
[/TR]
[TR]
[TD]Item Grade[/TD]
[TD]Standard Replacement[/TD]
[/TR]
[TR]
[TD]Maximum Pressure Rate (psi)[/TD]
[TD]6.5[/TD]
[/TR]
[TR]
[TD]Minimum Free Flow Rate (gph)[/TD]
[TD]40 GPH @ 1800 RPM[/TD]
[/TR]
[TR]
[TD]Minimum Pressure Rate (psi)[/TD]
[TD]5[/TD]
[/TR]
[TR]
[TD]Outlet Count[/TD]
[TD]1[/TD]
[/TR]
[TR]
[TD]Outlet Size[/TD]
[TD]1/8-27 NPSF[/TD]
[/TR]
[TR]
[TD]Outlet Type[/TD]
[TD]Threaded[/TD]
[/TR]
[/TABLE]

 

The second pump has higher pressure, so you will accomplish nothing by replacing the original.

 

I was hoping to see an answer to this. I've had the problem with non responsive idle screws. I assumed it was because of dirt and crud in the circuit but it didn't make much difference after I cleaned it up. I'm sure this is a symptom of something, just don't know what.

 

Remember guys that the idle screws are only for the idle. Anything above idle and those screws have no effect on the carb functioning at higher revs. If these screws are not functioning at idle then there is a problem with the carb or a vacuum leak or a wrong gasket.

 

take compressed air and a blower with a rubber tip pull the needles and give it a blast

 

Take it off, put it in box, send to these guys.. reinstall, smile at how well it runs...

http://www.guaranteedcarburetors.com/

I can't say enough about how awesome it was to simply bolt on the carb and it was perfect out of the box..