I Need Some Help Getting My Cj5 To Idle Right

59 cj5 F134 with carter yf938sd. Last 10 years has ran perfect no issues. Late fall it started idling poorly and lots of I'd call it black smoke and trying to die when stopped at a light. Seemed like it was flooding to me. So I rebuilt carb and didn't see any issues with it but with a kaiserwillys.com kit. Didn't fix it. I'm pretty good mechanically but not well versed in carbs.

So late in last year I stored it for the winter and now weather is getting nice I want it going good for this year. I ordered a full tuneup kit from rfjp.com cap rotor points condenser 12v coil autolite 295 plugs gapped to .030 new plug wires set points to .020 and verified dwell at 42 degrees set at 5btdc I also ordered another carb kit and rebuilt it again from mikes carburetors in Chehalis wa with supposedly the correct float spring loaded. Set float at level with carb top without gasket which I think was 15/32 and tested float in boiling water no leaks found.

It idles poorly but stays running rpms seem to kick up about 300 rpm rhythmically and vacuum flutters low when it does and picks back up and repeats. Tried changing idle speed up and down and tried different mixture screw settings I can't figure this thing out. Sounds like it might need the valves adjusted to me but I added a video to YouTube since I've never had much luck added photos or videos here.

I tried using a different yf carb and it runs perfectly with no rough idle telling me it's definitely a carb issue

https://youtube.com/shorts/SOLAKRS8Eas?feature=shared

 

If other carb it r s fine then gotta be in the carb. I’m sure Scoutpilot will chime as he knows his stuff.

 

Generic carb rebuild kits for Carter YF carbs may not have the correct float valve. A quality kit needs to be Jeep-appropriate.

The carb can very sensitive to incoming fuel pump pressure. Jeep applications had a smaller float valve orifice, to reduce flooding in "rough service." (Some owners have found it helpful to add an in line pressure regulator as a "fix" but the cause is actually having the larger - wrong -valve orifice, which places greater force on the needle.)

Also there are different float settings for different valves, such as spring loaded, or rubber-tipped. The float height must be specifically correct to the valve used, or flooding can result.

 

I will second the call for a vacuum leak check around the throttle. Rebuild kits do not address the wear that occurs in the throttle shaft bores and on the shaft itself. Over time the lateral forces applied to the shaft and bores wear each into an egg-shape. There's the leak. .005" wear is a leak. You can use a propane torch (obviously unlit) or Ether (starting fluid). However, if your idle setting is 800 or higher, you will likely not be able to hear the change in RPM when the test is done.

 

dont know if its relevant but my old yf would build crap in the bottom of the bowl clogging the idle jet slightly resulting in the surge or gallop you describe a good cleaning helped me.

 

I looked for vacuum leaks and found none using starter fluid and using smoke machine. It kicks up the slightest bit at throttle shaft with starting fluid but I switched just the lower part of this carb with the other carb and it ran the same with all swapped parts combos except center main body. I'm wondering if my problem might be metering rod adjustment but I don't know if that will cause this issue I'm having. I saw some videos on YouTube how to adjust, but I couldn't tell where they said or to make changes to metering rod. They weren't zoomed in on the part they were referring to and lighting in Video wasn't great for that kind of detail

 

I fought my metering rod adjustment til I finally figured it out. Having that tool mentioned in the article above helps a lot, at least for me. T109-212

https://www.ebay.com/itm/2651300697...1291&msclkid=4c6d7a21e8491651f6a51fd31fd0c07a

 

If you want to explore possibly having your problem carb professionally rebuilt, send a PM to Scoutpilot above. He runs Old Jeep Carbs LLC ( https://www.facebook.com/oldjeepcarbs/ )
and is a true expert on these carburetors. He rebuilt the Carter W-O on my '42 GPW a few years ago, and it has never run better.

 

Cap the vacuum line to the fuel pump and go for a drive.

Here are notes from BrianP who rebuilt mine:
https://flic.kr/s/aHBqjA9jxK

 

That's not your carb crapping. That stuff is coming from your fuel tank.

 

That tool is essential for proper metering rod adjustment.

 

you can try the old trick of placing the palm your hand over the carb opening (sealing it off) while the engine is running at a higher RPM, holding your hand there until it stalls out. That creates a large amount of vacuum in the carb I guess, and can sometimes clear up the passage ways. I did that on my 46 when it was stock, and it did run better afterwords.

 

"verified dwell at 42 degrees set at 5btdc" That's too late for 87 or 91 octane. Try a vacuum tuneup.

 

I will get it ordered

 

That's a good idea, just went and tried it several times and made no difference

 

I've heard the carb kits supplied now have the wrong parts for our carbs? Which parts are wrong specifically? Maybe the new idle jet tube that is installed from kit in my carb?

 

The Low-Speed Jet often won't have the correct size tip (#70 drill bit size) in the new reproduction kits. Pete DeBella sells a good NOS kit.

 

Post #4.

 

Jeep now idles very good. Seems to be fixed. Just wanted to thank everyone for the help.

I bought the special metering rod holding tool carter t109-212 but couldn't get it installed throttle was backed out and held closed with shaft held down tool didn't slip on seems like tool was too short. But I also bought an ultrasonic cleaner on Amazon 10L capacity.

I disassembled and cleaned carb again found debris in low speed jet cleaned it out and seems like it should have had a .028 orifice which it seemed much smaller than that but I couldn't measure it. I tried to fit a .028 drill bit through hole and it wasn't even close to fitting.
First soaking carb and parts in Berryman carb cleaner 1 gal for 30 min then I rinsed and placed in ultrasonic cleaner for 30 min at 175 degrees. And reassembled installed on Jeep and idles basically perfect.

I still need to tune it with vacuum gauge and timing light rpms etc but not today.

Seems like weather will be nice this week I will try to drive my 48 cj2a instead for this week

Thanks again everyone