Motor craft 2100 upgrade

[Laney668]

I recently bought the motorcraft 2100 1.08 for my 87 CJ7 to mount on a AMC 258 i6 / 4.2l . Carb is mounted and all gaskets are sealed. My problem is that the jeep runs fine when it is cold. As in just recently been started. Revs fine, gains speed fine idles great. I checked the timing and adjusted the mixture screws sveral times. Once the jeep has reached its operating temp it runs horribly. When you press the gas the engine completly shuts off. Then is very hard to get re started. Idle is horrible at this point as well. I have checked fuel line pressure and the carb is getting plenty of gas. I even thought it might have been vapor lock from the way the fuel line was routed. I rerouted the line and insulated it still getting the same probelm.

I believe i have narrowed it down to a vaccum issue. My directions i received were not very detailed about how to hook up the vaccum lines. Just wondering if anyone has a diagram or could send me pics of the setup of vaccum lines. Thanks guys any other ideas would be greatly appreciated.

 

[IOPort51]

I would check the lines coming from the CTO switch.

 

[TDHofstetter]

You should NOT have been adjusting idle mix screws or timing while it was cold. Those are both for adjusting AFTER it's reached full operating temperature.

When it's warmed up, does the choke open properly? It should be fully open at operating temperature.

Did the carburetor get rebuilt?

 

[Laney668]

Jeep was not tuned when cold. I waited till the jeep was warmed up than would adjust mixture and checked timing when the problems started occuring. The carb was completely rebuilt. Choke is setup for manual pull. Jeep idles fine cold and warmed up but will not drive after it is warmed up.

 

[TDHofstetter]

Ok. That's reassuring.

So... it's running too lean (or acting like it's running too lean). The most likely cause is a bad vacuum leak (as you originally suspected), which can be found with a spray can of either starter fluid or carb cleaner - spray it all around the carburetor area with the engine warmed up & idling as best it can. When you hit a vacuum leak with it, the motor'll speed up. Makes finding a leak quick & easy.

Has it ever (in your possession) run correctly when it was warmed up? If not, look hard at the EGR and the power brake booster.

The motor SHOULD run FAIRLY decently (not for everyday use) with all the vacuum lines disconnected & plugged.

It can also act like that if it's getting really poor spark - from really bad spark plugs or a very weak coil. Points, if you HAD points... but you've got electronic ignition.

Did you take a Carter BBD off the Jeep? Have you done the Nutter Bypass for the distributor yet? If not, it may run very poorly until you do.

 

[plumcrazy]

I was just about to ask the same question. I took the CJ out for a ride today and it started up and ran fine cold, once it warmed up and you step on the pedal it acts like it's out of fuel or something. Never did this before, I'm assuming it's a carb issue, but not sure how to verify that. Been looking for a 4bbl set up anyway, maybe now it the time. I have the Motorcraft ignition box (new), new plugs and wires. When you turn the key to the run possition but not running, should you have atleast 12v to the positive side of the coil?


Oh yea, all the emmisions stuff is gone.

 

[TDHofstetter]

No. You should have SIX volts to the coil when the key is turned to "run" but not to "start". You should have TWELVE or so when it's cranking.

When the motor's running (or when the ignition switch thinks the motor's running), the ballast resistor is between the battery & the coil. That ballast resistor was selected to hold coil voltage down to 6V.

Plum, how's the bowl level in your carburetor? How long has it been sitting without running (old gas?)?

 

[plumcrazy]

I haven't run it to much lately. It's not old gas though, just put some in it. Fuel gauge doesn't work and thought I may have been out of fuel, that wasn't the case. I'm sure it needs a rebuild, but the tag is missing off the carb and NAPA said I needed that number to asure the correct rebuild kit.
Never did a rebuild, but thier's a first for everything.

If any of you know of a good NAPA part#, please pass it on.

 

[TDHofstetter]

Which carburetor? If it's a 2100, any Motorcraft/Autolite, kit for that model carburetor should work.

Just for starters, try running about two jugs (together, not sequential) of carburetor/fuel injector cleaner through it now. You may get lucky...

 

[plumcrazy]

No. You should have SIX volts to the coil when the key is turned to "run" but not to "start". You should have TWELVE or so when it's cranking.

When the motor's running (or when the ignition switch thinks the motor's running), the ballast resistor is between the battery & the coil. That ballast resistor was selected to hold coil voltage down to 6V.

Plum, how's the bowl level in your carburetor? How long has it been sitting without running (old gas?)?

Is it possible it's a float issue? If there was a hole in the float, it shouldn't matter if it cold or hot, right? How do I check the bowl level?

 

[IOPort51]

I know this is silly but did we change the fuel filter to a single outlet??

 

[Cheepjeep85]

td asked a question that didn't get answered. did you do the nutter bypass on the ignition. you said all of the emissions stuff is gone, but just taking the carb and all of the vaccum that goes with it isn't enough you have to rewire the ignition. otherwise the computer is still controlling the timing which isn't good seeing as its not getting any feedback from the rest of the system. to rewire it you need to clip the purple and orange wires from the dist to the firewall, then you need to connect the same wires coming from the dist. directly to the purple and orange wires coming from the plug that comes out the ignition cont. mod.

 

[Laney668]

Im going to try to do the nutter bypass and see if that works. I tried to find a vacuum leak around the carb with a can of starter fluid but had no luck at finding a leak. When i first put this new carb on it ran fine. not perfect but decent enough to get around town. Then i mad the mistake of tweeking the mixture screws to try to get it to run a little richer. ever since then it has not wanted to run correctly.

 

[MDJEEPER]

td asked a question that didn't get answered. did you do the nutter bypass on the ignition. you said all of the emissions stuff is gone, but just taking the carb and all of the vaccum that goes with it isn't enough you have to rewire the ignition. otherwise the computer is still controlling the timing which isn't good seeing as its not getting any feedback from the rest of the system. to rewire it you need to clip the purple and orange wires from the dist to the firewall, then you need to connect the same wires coming from the dist. directly to the purple and orange wires coming from the plug that comes out the ignition cont. mod.

Completely agree. I am also quickly learning that the computer cannot possibly operate the engine correctly without all of the sensors in place.

 

[plumcrazy]

I didn't mean to hijack this thread, just wanted to let you guys know I found my problem (I think). Apparently I didn't tighten my carb down good when I put it back together. I got a good full turn on all four nuts, took it for alittle ride and it's running much better. It wasn't up to full operating temp, I guess a long ride will tell.

 

[Laney668]

im about fed up with this jeep i have run the vacuum lines every way possible and jeep will still not run at operating temp. Everytime you hit the gas the motor bogs down and has a sucking sound in the carb. I have dont timeing i have check for vapor lock i have checked for fuel i even thought the jeep was over heating so i took out the thrmostat and have done the nutter bypass still doesent run! if anyone is in the southern maryland area could you please help me or if anyone could send me photos of how the vacuum lines are supposed to be run i would greatly appreciate it.

 

[TDHofstetter]

SIMPLY, the carburetor doesn't need many vacuum lines at all for the Jeep to run. It needs the big fat vacuum line for the brake booster (unless the booster is leaking, which is possible - that'd keep it from running when it's warmed up), it needs a very short vacuum line to the choke pulloff, and it needs one ported vacuum line directly to the distributor. The rest are all to either make it run a little better or to keep emissions down.

Is the choke adjusted correctly?

Is the brake booster leaking? Try taking that vacuum line off and plugging it.

When you did the Nutter bypass, did you leave the mixture pins lean or rich or in the middle somewhere?

 

[dalefan88]

did you down size the jets? mine had 52 or 54s. they need to be 46 to 48s. i have 46s in mine and it runs fine.

 

[TDHofstetter]

What's your altitude, DaleFan88?

 

[Laney668]

I dont have a brake booster. The choke is a manual pull. I know i need one for the PCV and one for the dist advance. But can i just cap off the CTO switch(for some reason its only a two port?) and the EGR valve? I left the mixture screws at about 2 3/4 turns out.