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Unread 04-03-2010, 10:09 PM   #1
samini
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Need Help with motorcraft 2100 carb

Okay I have a 4.2 L 258 that I have a motorcraft 2100 carb on, I just did the nutter bypass, and I hooked up all the vacuum hoses as shown on the diagram on my picture (This vacuum diagram was recommended on these forums)

http://www.jeepforum.com/gallery/dat...um_Routing.jpg

The jeep only idles good when I pull the vacuum hose off the canister (the green one in the picture) that hose from the canister is "T'ed" off of the PVC hose. If I plug that hose (which has plenty of suction) or plug it back into the canister the engine stops immediately as if it is getting no air.

Any Ideas?

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Unread 04-03-2010, 10:16 PM   #2
Skerr
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I may not understand completely, but it looks like your PCV is plugged into your canister. It should be plugged into the large port at the base on the back of your carb. But I don't have a canister so I may not be any help!
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Unread 04-03-2010, 10:20 PM   #3
samini
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It is plugged into the large port at the base of the carb, but according to the diagram it is supposed to go into the canister too. even if I just make it go right into the port at the base the it stalls. I have to leave that port open for the engine to idle.
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Unread 04-03-2010, 10:29 PM   #4
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Hmmmm, by pulling that connection off you create a massive manifold vacuum leak. Engine should die almost immediately when you do that. The diagram you used is correct. There is manifold vacuum going to the canister but the valve is held shut until the purge signal from the CTO tells it to open and purge the fuel vapor.

Did you do the nutter and carb swap together?
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Unread 04-03-2010, 10:35 PM   #5
samini
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Yes I did them together. Yes there is a huge vacuum leak. You can feel it on the hose I pull from the cannister. It actually idols really well, but drivability is not good and it does stall out when stopping or shifting into reverse (its automatic transmission)
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Unread 04-03-2010, 10:54 PM   #6
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For it to be able to run like that I would think the carb must be running extremely rich to compensate. Did you go through the process of setting the mixture screws using a vacuum gauge? The power valve could be bad and dumping fuel as well.
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Unread 04-03-2010, 10:56 PM   #7
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The mixture screws are almost all the way out...does this mean that it has more air or less air going into it?

What is the power valve?
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Unread 04-03-2010, 11:09 PM   #8
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All the way out is rich. I set mine by using a vacuum gauge connected to manifold vacuum. Turn the mixture screws all the way in until they lightly seat. Don't crank down on them. Then back them out evenly together to about 2.5 turns. Start it up and set idle. Turn each screw in 1/4 turn together and watch vacuum gauge. Looking for the highest steady state vacuum reading. Eventually you will go too far and the needle with start to bounce and the engine should stumble. Back them out slightly until it is stable again and that is the leanest idle mixture.

The power valve's job is to dump more fuel when you are on the throttle hard. They can go bad and when they do they dump fuel all the time.

Last edited by VACJ7; 04-03-2010 at 11:31 PM..
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Unread 04-03-2010, 11:21 PM   #9
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Ok, first did you retime the engine after the bypass? Second, did you rebuild the carb, buy it rebuilt, or just find one and try to run it? After taking the computer out of the equation your timing will be off since the ecm controlled it to start with. The mixture screws should be no where near all the way out. You are putting to much fuel into the carb itself. You should turn each mixture screw all the way in making sure to gently tighten them. Do not, I repeat, do not screw them in really tight, you can damage the screws this way. Once you have them all the way in slowly turn one at a time back out 2.5 turns ( two and a half turns). 2.5 turns is a base tune for the carb mixture screws and should keep the carb running fairly good. Mine carb is tuned slightly passed 2.5 turns atm.

The power valve is located underneath the accelerator pump. The pump is located on the front of the carb (toward the front grille of the jeep) and has an arm on it with a lever that connects to the actual gas pedal linkage. If it is bad then it will let fuel dump in the carb as well. One way to tell what is going on with the jeep is to pull the spark plugs. The electrodes should be a redish brown color, but if they are black then you are running it way to rich and the jeep is loading up. If the electrodes are white then the jeep is running to hot which means a lean enviroment (not enough gas).

Here is how my 83' jeep is setup: The PVC from the front of the valve cover ties into the big port on the back of the Motorcraft 2100. T'ing off from that is a second line that runs straight into the vapor canister as well. I have one more question, what happens if you pull the vac line off the canister and plug? Will it still idle?

Hope some of that makes sense, I spent some long nights with my Motorcraft 2100 fine tuning it and I love it 100%. I'll keep an eye out on this thread and try to help as much as I can. Goodluck!!!
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Unread 04-03-2010, 11:36 PM   #10
samini
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Okay I turned them all the way in and backed out 2 1/2 times and it worked, but the idle is terrible and stalls out. I don't have a vacuum gauge. so can I do it by ear?
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Unread 04-03-2010, 11:53 PM   #11
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The carb should run at 2 1/2 turns and idle, unless you have a bad vac leak. The small to large adapter plate is a one point of major vac leaks, or at least it was for me. That could be one place to look. The gaskets with the kit are horrible and I ended up making my own. Just something to check.
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Unread 04-04-2010, 12:55 AM   #12
samini
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Okay I checked for vacuum leaks with some starter fluid and there is none. I get rough idle still and stalling. I have tweaked the distributor a bunch without better results and I have adjusted the pins without better results. Any more ideas?
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Unread 04-04-2010, 06:38 AM   #13
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Did you adjust the timing since doing the Nutter... should be around 9*?
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Clay's Build Thread
http://www.jeepforum.com/forum/f8/cl...hread-1061897/
Scott's Build Thread
http://www.jeepforum.com/forum/f8/sc...5-cj7-1147913/
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Unread 04-04-2010, 07:47 AM   #14
samini
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How exactly do you adjust the timing? I know how to rotate the distributor, but I am a little unsure about the timing. Do you need to move something else?
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