Adjusting float level on a MC2100

Hi,
Got a new, properly working, fuel pump in the cj last week, and now i'm having problems with the carb flooding out when I hit the big bumps.

I know that the 2100 is supposedly pretty good for off road, so I'm thinking I need to adjust the float level down a bit.

I've looked here:

http://www.earlycj5.com/forums/showthread.php?t=38117&highlight=mc2100+float&page=2

and here:

http://www.nmr.mgh.harvard.edu/~reese/jiffykit2.jpg

!
I think I have a pretty good feel for what needs to be done, but I dont know how low to set it. Should I just eyeball it, and go down "a bit"? Does anyone want to run through the procedure for me, so I'm sure not to mess it up? Please!

Mc2100 experts, please enlighten me.
Thanks,
-Dante

 

I know the rebuild kit list a couple of dozen different applications, and each has its own float level. I can look when I get home - the kit supplies a paper ruler that's referenced to the plane across te top of the bowl. To measure, you can either turn the carb upside-down and let the float hang or lift it gently by filling the bowl or with your finger. IIRC the measurement is to the top of the float, not the fuel level.

To adjust, you bend the tang of the float up or down. You don't want to bend the whole float bracket - just the tang. I use a pair of duckbill electronics pliers to hold the bracket behind the tang and another small pair of pliers to bend the tang. Be sure to keep the tang level wrt the float bracket, or the needle will stick and you'll have a flood. Easy does it - it's a very tedious and fiddly thing to have to do.

 

Thanks,
I've also heard about people installing a pressure regulator in line for off road use. Most i've seen say 4-5psi. Anybody with experience with this?

I may try this before digging into my carb, especially sincei plan on going wheeling on friday, and want my jeep in working condition for it.

Thanks for the help.
-dante

 

Heard about it used on a Holley-Weber (the Redline carb often used on 258s) but not with Motorcraft. Lots of Jeeps do fine without one. Do you have the float dampening spring on this carb?

 

I dont know if i have the spring on this one or not. I've been reluctant to tear into a carb that been running well in most situations, so I've never had it open.

I may try to open it up today after work, or possibly tomorrow. If you dont think the regulator is worth is, I'll save the $.
Thanks,
-Dante

 

MC carbs, like almost all of them, are very crappy in rough offroading with lots of bumps. The float bounces around, the fuel bowl overfills, and you start flooding. Spring loaded needle and seats help, but I've never seen a cure. On the four or five trucks I've had with MC carbs, I would drop the fuel level 1/16 to 1/8 inch below the factory spec, then use an adjustable regulator to keep fuel pressure at 2 to 3 psi. This is plenty for low speed offroading. I'd kick the fuel pressure up to around 5 to 6 psi for road use.

The next trick is to recognize when you're going to flood. If you've been rolling over big roots or bowling balls for a few minutes, stop and let the engine settle for a few seconds once in a while to let the float level return to normal. This will prevent the engine from stalling most of the time if you get a particularly hard jolt.

 

There's a generic chrome regulator available from about a dozen companies that works great and can be found for $20 if you look around. It's well worth the money. The highest price I've seen on this regulator recently was $35 with a Moroso stamp on it. The one I have now says CR and was $15 a couple years ago.

 

Well I went out today, and i gave the float a slight adjustment down, but i didnt want to over do it. Its much easier than i thought it would be, so next time I'm having issues trail side, i might jsut open er up and adjust down further. I'm still going to try to find a regulator though, i guess it can hurt.
-Dante

 

The V8 fuel pump is spec'd to make 6-8 psi or something like that. If you look in the FSM, there's a listing of the output for both the 6 and V8 apps. It's not hard to imagine how surges of high pressure fuel could flood out the float bowl on bouncy terrain. Whether that's realistic or not, I don't know. If you compensate by adjusting the float low and limiting the fuel pressure, you could have fuel starvation under some conditions. Jeep did fit a float damping spring after 1972, but it's been missing on every commercially rebuilt carb that I've opened. Certainly the pressure regulator will give you another knob to turn if you have difficulty. Chicken soup at worst.

Lowering the bowl level will also lean out the mixture some... typical of carb fiddlyness; none of the changes act in isolation.

Dang carburetors! EFI is a better solution, but not for this discussion.

 

Well one day a propane system or truck avenger carb will make its way into there, but not for a while.


Anyhoo, I only lowered the float a tiny bit since I was apprehensive. It did seem to be set pretty high, less than 1/8" from the top of the bowl. The jeep still seem to run on, idle smooth, and rev up just fine. I'll see how it does on the trail friday.
Thanks for the advice!
-Dante


P.S. For someone with little to no automotice carb experience, it was pretty interesting to watch the carb run with the top cover removed. Gave me a much better understanding of how it works. I've worked on motorcycle carbs, but its different.