Trying to lean it out

[SenorCole86]

Hey guys, been a long while since I visited, but I have a question. I've got a motorcraft 2150 carb in my CJ along with the GM HEI from an '80 blazer and a painless wiring harness. Don't think that last one would make any difference unless it was reducing the voltage to the dist or something, which I haven't checked yet but I did remove the ballast resistor, so I don't think that's it. Has anybody else with this setup had problems with running really rich? I know I am and was wondering how one went about changing the air fuel ratio on one of these things, and how do you know when you've got it right? I can change the idle mixture, but that just ain't enough. Others have suggested changing jet sizes, but I think I remember hearing from one of y'all that that hardly changes anything. Any help at all would be greatly appreciated guys. Thanks a lot.

 

[Magua308]

I am running the 2150 on my 89 YJ 4.2. There are two screws at the front corners on the base of the carb, those adjust the fuel mixture for each bbl. What I would suggest is to run both screws all the way in (the engine should not run when they are all the way in, if it does, you have other problems) then bring them out one half turn and start the engine. It should idle really rough, bring both screws out evenly until it idles well then go a half a turn more. That should get you really close.

 

[SenorCole86]

Right, that's the idle mixture. I can set that, and have it set to peak RPM. Thanks though. I was talking about making float adjustments or jet size changes or whatever it takes to lean it out. I just now thought of the accelerator pump. That should help some, right? I'm gonna go mess with it.

 

[nica89yj]

I also have a motorcraft carb on my 89 yj, Its a 1.08 venturi I was wondering what size u are running SenorCole86? I managed to obtain perfect idle on my jeep and iam really happy with the carb, but i think iam running rich. Is it possible to idle perfectly and still run rich? My jets are #46 i was also wondering what i could do to lean out a bit?

 

[SenorCole86]

Alright, I read that a whistling noise coming from your carb is msot likely a busted purge valve. If I understand the function of a purge valve correctly, a busted purge valve will cause extra fuel to be fed to the engine . . . right? That's my next objective then.

Nica, you say you think you're running rich? Pull one of the plugs and see if it's black or sooty to check if it's rich or not. And it is possible to idle just fine while running rich. It's even possible to accelerate just fine as long as it ain't too rich. You jsut won't be getting all the power you can and it's not too good on your fuel mileage either. Somebody correct me if I'm wrong.

 

[Laph]

nope thats all right, if none of that work you will have to drop your jet sizes down if you can't get it to lean out. but that should be a last resort, what size jets you have in it now?

 

[SenorCole86]

There's size 47 in there now.

 

[Thord]

Ok guys, I got an 86 cj7, 4.2, 2100 carb with 1.08, i had a hard time getting it to idle below 900-950 but finally got it to about 750 with a decently smooth idle. it does run rich still. my question is back to the purge valve. i read an article that stated the power valve should be replaced if you are running rich. this is supposed to keep extra fuel out. i tried to replace it but coulnt find the right part. does anyone know about this? or have a part number?

thanks

 

[SenorCole86]

I've heard people say that you need to find a power valve that doesn't open up until 16 inHg of vacuum. You're gonna have to go to a carbuetor rebuilder for that. I just looked under "carburetor" in the yellow pages (imagine that). Good luck bud.

 

[Brosch]

First off; If this is a recent development, your symptoms also could be a vacum leak. Check your hoses and also make sure the intake manifold bolts are snug. A stuck or worn out PCV valve will do it too as will a blown diaphram in the Dist Vac Advance. But I wouldn't change a bunch of stuff hoping to accidentaly hit the right thing. If you feel you have a carb problem, and the engine ran fine before this, remove the carb and put a kit in it. It's not that hard to rebuild a 2100/2150 and the 'Niehoff' kit has everything you could want, including a chart of the proper settings for the float, and a proper power valve. If you have a phonalic (sorta) float you can test it by laying it in the sun for sevarel hours to dry it out, then droping it into a jar of gas for several hours, and see if it soaks up fuel and sinks a little. While it's apart you will spot the jets in the bottom of the bowl. These cost about 7 bucks a pair and once you see how simple the carb is you can experiment with different jet sizes. And life will be grand.

 

[Thord]

Thanks, you were right, it as actually the manifold gasket and adapter gasket were both pretty worn, replace them and adjusted the jets down to reduce fuel and now runs like new.

Thanks

 

[slo-wrench44]

i do know that if the engin is running rich , it will run a little hotter. mine did this. i literaly just pulled the carb out of the box and hooked it up and tuned it to run and ran with it. i didnt even look at the float level. guess i got lucky till i did a road trip to NC and the southern heat in july had the temp climbing... i thought it over and changed the jets down 2 sizes and set the float level and it dropped 7 degrees .... i was happy to say the least