Zenith idle running rich

[artpeck]

I just finished servicing the zenith and everything works fine but for it idling very rich. The idle mixture screw doesn't seem to do anything. All the way in or all the way out and nothing changes. I have tried a new screw (though the old looks perfect) and nothing. And the seat also looks fine from what I can see. I know there are a bajillion zenith posts here and I have read a lot of them. This issue seems to have come up before but I haven't found the solve. Any ideas appreciated.

other relevant info. Low mileage 33k barn find SIII. New fuel pump. All gaskets and the o ring in the carb replaced. Choke is open and moves freely. Float is perfect. Carb and is flat and seals. Yet at idle it is rough and black smoke. At speed it is fine so seems limited to an idle adjustment.

[busboy]

Sounds like the float chamber is too full from either the float level set wrong, or is too low (leaky float) or the float shut off seat/valve is leaking.

[Revtor]

check the anti dieseling solenoid.. If yours is shot, you might actually not even be running on the idle circuit. pull the solenoid and see if it opens and closes with 12v. it should be open when the engine is running, and allowing the idle circuit to function and closed when the power is removed, closing off the idle circuit. This is supposed to keep the engine from "running on" or dieseling when the engine is hot and shut off... -I think I got that right. anyway, check the solenoid.

~Steve

[jac04]

Also check to make sure the throttle plate is closing enough at idle. The idle circuit only comes into play when the throttle plate is closed enough.

[artpeck]

Thanks much to all of you. I will check this today. Art

[artpeck]

check the anti dieseling solenoid.. If yours is shot, you might actually not even be running on the idle circuit. pull the solenoid and see if it opens and closes with 12v. it should be open when the engine is running, and allowing the idle circuit to function and closed when the power is removed, closing off the idle circuit. This is supposed to keep the engine from "running on" or dieseling when the engine is hot and shut off... -I think I got that right. anyway, check the solenoid.

~Steve

I pulled the solenoid and started the truck. The plunger is out whether off or under power. In other words it doesn't move at all. I can pus it in easily but it doesn't retract under power. That said with it out the problem is still the same and no change in how it is running. I am assuming (correctly?) that with it out the idle circuit should kick in?

[Revtor]

With the solenoid "off" the idle circuit should be bypassed.. or blocked.

There is a good few pages in the green bible about the Zenith. In the June/July 1997 NoCal ROvers club bulletin they have a good few page article about the carb... that was helpful too.
heres the link to the PDF:

http://www.google.com/url?sa=t&rct=j...45175338,d.dmg


Bust out the diagrams and make sure everything is in right, lapped flat etc etc.. Its all pretty simple, you'll get it figured out!!!!!
~Steve