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How to - Nutter Bypass

414K views 505 replies 176 participants last post by  KDub1984CJ7 
#1 · (Edited by Moderator)
Ok, for all those who want to perform the Nutter Bypass to eliminate the Electronic Control Module from your '83 and later CJs and YJ's with 4.2L engines & BBD carb, here's the how to.

I know I had a lot of questions before doing it about how to, etc., and I've seen a lot of others asking questions, so I figured why not create this so that, hopefully, most questions are answered. A little preparation on the front end saves a lot of headaches on the back end, right?

This is NOT a 'why should it be done post? For that, you should do other searches and then come back to this if you decide to do it.

It's easy to do, and it did benefit me. I no longer have the rough idle, including my Jeep's 'cough' during idle. My gas mileage prior to the bypass was 16.2mpg. After filling it up and emptying a tank, it was at 18.7mpg. That was with a lot of stop and go and even a little mudding.

Also, a BIG THANKS!! goes to Mike Romain, who read over, corrected, and helped a lot with this write up. :cheers2:

So without further ado, here it goes. Step by step (with pictures!!). :2thumbsup:

Stepper Motor Needle adjustment: Steps 1 & 2

Step 1: Adjust the stepper motor needles in the carb so that the shoulder sticks 1/8" into the carb.

Stock stepper pins run in the middle of their travel which is when their shoulder is 1/8" to 1/4" away from the carb wall (closer to 1/8" is preferable). Several people have set their pins at this level and have reported improved results over the 'full rich' setting in John Nutter's original setup. Some of these jeeps have also passed emissions testing with the needles set in this position. Of course, it's a Jeep thing, and your results may vary.

To get your stepper pins the way you want them, the easiest way would be to remove the stepper motor from the back of the carb and adjust the pins, then re-insert and affix the motor to the carb. Ensure you did not move the pins when re-inserting the motor.

Another option is to adjust your idle mixture screws on the front of the carb while the engine is running: Out (counter-clockwise) - to have the stepper pins move into the carb and create a full, rich condition, or In (clockwise) - to have the pins move into the stepper motor to create a more lean condition.

Step 2: If you choose to adjust the stepper pins using the idle mixture screws method, once the stepper pins are at the level you choose, turn the ignition off and unplug the electrical box from the back of the stepper motor (remains unplugged forevermore).



Re-routing wiring: Steps 3-11

Here is a link to a diagram of before and after wiring... Blog | Earthlink

Step 3: Find the orange and purple wires at the distributor.



Step 4: Follow the wires through the wire loom to where they enter the firewall (it may be necessary to remove the loom).

Note (Read prior to Step 5): It is sometimes recommended that you do not cut into the wires inside the loom. Rather, add two new twisted wires for the full length. One reason is YJ 258's have different color codes in the harness than CJ's. This will also leave it as close to the original as possible so future owners, or you, may change it back if this is desired. In this case, you could add two new twisted wires from the Ignition Module end to the Distributor end.

I did not do it this way. I went ahead and cut the wires at the firewall. If you prefer to do it the way I did, follow ahead. If not, perform the following steps by adding new wires end to end.

Step 5: Cut wires 3"-4" from the firewall. I brushed my unused ends with 3m electrical coating, then wrapped them in electrical tape just because I felt better about it rather than just leaving them exposed.

Step 6: Find the orange and purple wires at the ignition module (under the washer fluid reservoir). I had to remove my washer fluid and overflow reservoirs to get to the module.



Step 7: Cut the wires at the ignition module. I protected the unused ends here the same way as in step 4.

Step 8: Cut two lengths of extra 16 gauge wire to reach from ignition module to the firewall where you cut wires in step 4. Or to the distributor if you chose that method. Hint: If using the same color wire, mark each end of one as 'purple' and the other as 'orange'. Or, do as I did and simply color both ends of one wire, so you know which wire goes to which color once they have been twisted.

Step 9: Twist the two lengths of extra 16 gauge wire together just as the stock orange and purple wires are twisted. (This helps with insulation from outside electrical interferences). Hint: I read this trick elsewhere, and it really helped. Put one end of the wires in a 'C' clamp or something similar and the other end of the wires in an electric drill. Then twist. This made the process a lot easier. Twist until you meet about the same coil as the stock wires.

Step 10: Attach your extra 16 gauge wire from the orange at the ignition module to the orange from the distributor.

Step 11: Attach your other extra length of 16 gauge wire from purple at the ignition module to purple from the distributor.



Vacuum hose move. Steps 12-13

Step 12: At the carburetor, remove the vacuum line that is currently going to the distributor and plug the outlet you just removed it from.



Step 13: Find the ported vacuum line just behind the choke coil on the valve cover side of the carb and remove this line. Using a 'T', attach the distributor vacuum line to the other vacuum line you just removed.



Adjust timing to 8* BTDC. Steps 14-25

Step 14: Warm up the engine to operating temperature, then shut it down.

Step 15: Unplug the vacuum line at the distributor and plug it in.

Step 16: If using a timing light, follow the instructions to hook it up. Should be like this: Clamp the pickup onto the #1 plug wire, then hook up the negative lead to the negative side of the battery, then the positive to positive on the battery. Ensure no wires are in the way of fans, belts, or hot engine parts.

Step 17: Locate the timing marks on the front driver's side of the engine. The lowest mark is -2 degrees. You want the timing to be at the 6th markup. Each timing mark equals +2 degrees, counting up from the bottom.



Step 18: Loosen the bolt, which is below the distributor on the right hand side, slightly so you will be able to rotate the whole distributor.



Step 19: Start the vehicle.

Step 20: Take the timing light and aim it at the pulley to the left of the timing marks you found earlier. When the light flashes, you will see the notch in the pulley. You want it to be at 8* BTDC (+/- 2*). Check the timing marks on the front of your engine; however, on all in-line six cylinder engines, it should be the 6th markup.

To advance the timing move the ENTIRE distributor counter-clockwise. To retard the timing, go clockwise. DO NOT move the distributor by holding at the top. Move it from the bottom. You could get shocked otherwise.

Step 21: Turn the engine off.

Step 22: Lock the distributor in place by tightening the ½" bolt.

Step 23: Start the vehicle and re-check the timing. If it is of any, follow steps 18 through 22 again until it is right.

Step 24: Turn the engine off and clean up your mess, be sure to replace the vacuum hose you removed in step 15.

Step 25: Adjust the idle mixture screws on the front of the carb to the 'best lean' idle mixture and re-tune your carb.

Step 26: Enjoy a great running Jeep!!

Next for me...TEAM RUSH!!
 
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#48 ·
Step 2: If you chose to adjust the stepper pins using the idle mixture screws method, once stepper pins are at the level you choose, turn ignition off and unplug the electrical box from the back of the stepper motor (remains unplugged forevermore).
It would seem that you can plug the stepper motor plug back in so it looks, umm, won't burn the plug. Thoughts ?
 
#49 ·
The computer can still kick it so if you unplug the computer itself, then Yes, that's OK.

The nutter just takes the computer out of the ignition loop.
 
#53 ·
#55 ·
Twoleos,
May I make the suggestion to not cut any wires when you start removing them? I found that you can simply unplug them and the whole emissions harnes will come out. You will need to add one wire for the choke. I believe this is what you are referring to when you asked if the choke is affected.
You can unplug things one at a time, and test drive, and if you like it then you can remove the harness intact, and if you ever sell the Jeep (not that you ever would), the next guy can hook back up if needed.:thumbsup:
 
#58 ·
I don't think luckycheesehead will mind I am going to add a quickie on the vacuum lines after the Nutter for the Carter BBD here.

Here is what makes a decent runner that will pass emissions in Canada:

The PCV system including the canister and CTO valve and the EGR maybe as well as a ported line to the distributor. I also want the air cleaner lines working to prevent carb icing, emissions wants it for faster warm up.

On the Stock Carter BBD or Carter-Weber BBD like mine, the drivers side back corner nipple goes to the air filter TAC (hot air flaps).

The big driver's side port on the bottom goes to the power brakes.

The center back big one goes to the PCV with a T fitting for the canister purge. If you have a solenoid on this line, toss it as a recall, only leave the T for the canister purge.

Back passenger side to choke pull off.

The valve cover side center goes to the distributor. It 'can' T for the CTO feed 'or'..

The front drivers side corner one goes to the CTO valve. From the CTO, a line goes to the canister purge signal 'and/or' one can be fed off this purge line to the air filter TVS and from there to the EGR.

Some folks feed the CTO to the TVS and then split off the line coming from this to make the canister and EGR lines.

Everything else is pretty much trash.
 
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#59 ·
is there a diagram for those, my new 7 dosnt have any vacum lines on it
 
#61 ·
Mike, maybe a 360* pic w/the air cleaner on/off so some can get a visual of the lines and how they are hooked up. I'm sure this will help clear up a lot of questions in this area.

Jim
I have camera battery issues right now, the charger is packed in a box in the storeroom after a move idea...

Dale did a great site on the 258, here is his links:
http://home.sprynet.com/~dale02/
http://home.sprynet.com/~dale02/vac-egr.htm
http://home.sprynet.com/~dale02/vac-tac.htm
http://home.sprynet.com/~dale02/vac-mcu.htm
 
#62 ·
?
Mike, if you do not have the guts for the stock air fliter will the set up still work w/out the TVS thingy. :)

If I don't have a SOL-VAC vacuum how would I hook this up/to what? Meaning I have the SOL-Vac but all I have routed is the CTO, dizzy & the canister hook up.

Oh, I cleaned my air fliter can & then cleaned out the pcv valve w/ spray brake cleaner, so far no oil in the a-filter can. The pcv was clogged some what.

P.S. I understand about the move, we are gonna move again in May. :(
 
#63 ·
?
Mike, if you do not have the guts for the stock air fliter will the set up still work w/out the TVS thingy. :)
Yes, you can do without, it just makes the engine a bit boggy when it is cold, so warm up time should be maybe a bit longer.

If I don't have a SOL-VAC vacuum how would I hook this up/to what? Meaning I have the SOL-Vac but all I have routed is the CTO, dizzy & the canister hook up.
You can just ignore the sol-vac and if you have, use the screw for the curb idle. Mine didn't even have the screw in it for the sol-vac, only the lower curb idle screw.

I have heard reports of the vacuum/electric part of the sol vac, if everything stock is left, will still work to bump the throttle up for an automatic or AC. You could wire the electric for the AC also easily if needed.

Some folks have added a fused 12 volt switch to this for a manual fast idle
 
#65 ·
On an 86 CJ7 you're supposed to cut the orange and purple wires in the loom before the firewall and splice them to the ignition module. Are you supposed to cut another orange wire and splice it together with the orange distributer wire running to the ignition module?
 
#66 ·
There is no 'orange and purple' in the loom, only an orange. The purple wire stops at the ignition module's plug and a new wire from there to the distributor must be added.

I am of the firm opinion the job is best done by running two all new twisted together wires directly from the orange and purple at the ignition module to the orange and purple at the distributor rather than mess inside the loom.

Having two new wires twisted together like the factory wires are twisted together for RF filtering is the best. Otherwise you have this lone purple wire that can pick up all kinds of stray pulses.
 
#70 ·
Wow!!! Great thread and great info!!!! I will be doing this bypass tomorrow.

Couple of questions though:
I have an 86' CJ-7 with the 258, with a Motorcraft 2100 carb for more power. I have trouble keeping freeway speeds up. Will this help by taking the ignition system out of limp mode?

Is there anything else that this bypass will effect?

Thanks and again, GREAT WORK!!!!! :cheers2:
 
#71 ·
Wow!!! Great thread and great info!!!! I will be doing this bypass tomorrow.

Couple of questions though:
I have an 86' CJ-7 with the 258, with a Motorcraft 2100 carb for more power. I have trouble keeping freeway speeds up. Will this help by taking the ignition system out of limp mode?

Is there anything else that this bypass will effect?

Thanks and again, GREAT WORK!!!!! :cheers2:
Well... the motorcraft carb is usually for a V8, it will work on a 258, but not as well as a properly tuned 6 cylinder carb. Lots of folks do use them though.

If I was going to use a V8 carb, I would want headers and a high flow exhaust so it doesn't just bog it out.

That Carter-Weber BBD you had on there was the better carb in my opinion. Tuned and nutttered, the BBD pulls mine to 75 mph in 3rd and 4th buries the speedo big time with no urge to test 5th for top end... It will also purr up sand pit/ravine walls at 400 rpm without a chug. Also gives 21 mpg...

I know I lose highway top end fast when my carb is set too rich. I have played with the high speed mix to see. That 2100 can have different jets put in it I think that may make it better for a 6...

That said, getting it out of limp mode should help a lot, it frees up the timing advance for one thing. It also basically shuts down several miles of those vacuum hoses, well in limp mode, not much is working anyway.

Here is a good site for seeing what is what:
http://home.sprynet.com/~dale02/
http://home.sprynet.com/~dale02/wire-sml.htm
 
#73 ·
Just curious how you know it is leaning out at full throttle conditions. If it is, wouldn't that indicate you don't have the correct main jets? How did you determine you have the correct jets? What altitude are you at? ( not familiar with OHIO topography...)
 
#74 ·
At full throttle, I notice the engine starts to ping and knock quite a bit. Now if I keep the RPMs below 2,000 all day long, the plugs are a nice brown color and it runs great. Now if I rev it over 2,000 RPMs pulling away from stops and then pull the spark plugs, they are a crisp white color. The white coloring of the spark plugs and the pinging indicates to me that it runs leaner as the throttle is applied. :dunno:

So the jets are perfect for the engine, just that upper RPM range that is giving me fits.

I sit at 1,000-2,000 feet range. I don't know exactly......
 
#75 ·
Well,
I got finished with the jeep around 9:00pm and just now are getting around the laptop. The bypass went well and smooth. Basically just two wires to run for me, and adjust the timing and carb. I took it for a short test drive and it made alot of difference between 2,000rpm and 4,000rpm!!! I was doing burnouts all over the place:teehee: I have yet to get the adjustment perfect on the carb but it seems to run really well. Everytime I floor it, it will cutout and pick right up. I am gonna run the jeep to work and pull the plugs to see how they look. My guess is that I am running a little rich right now. Thanks for the info and it really helped. :thumbsup:
 
#76 ·
Cool for a fast 'dead spot' test, unplug the EGR valve and block it's line. Lots of them will stumble after the Nutter with the EGR still working. Mine is like that so I just plugged the EGR back in come emissions time.
 
#82 ·
Not likely. It is technically illegal to remove emissions equipment, no matter it can still pass the emissions sniffer and gets better mileage...
 
#87 ·
You disconnect it and block it and you also need to change it's source to ported or over to the nipple on the valve cover side of the BBD.
__________________/QUOTE]

What do you mean by ported? and it is already connected to the valve cover side of the BBD from the factory. Plse explain.

Thanks
Stock, the vacuum to the distributor come from a diverter valve that mixes manifold vacuum and ported vacuum via a CTO valve according to how hot the engine is.

Or it came from the drivers side above the brake feed for pure manifold vacuum depending on the flavor of the emissions.

I have never heard of a stock feedback 258 having pure ported vacuum, but I haven't seen them all....
 
#89 ·
Just wanted to say thank you to all for constantly updating this thread! All my questions were answered in this or the "nutter bypass trouble" thread.
I just finished the bypass and went for a quick test drive. I can't believe that all the pinging is gone, and she rev's smoothly. I think I still need to fine tune the carb but I am impressed with the early results.

Thanks again!:thumbsup:
 
#90 ·
Guess I have to change my signature from "soon to be nuttered" to just "NUTTERED"!
 
#91 ·
timing

Standing on the passenger side of the jeep looking at the distributor.. do I need to rotate the distributor clock wise or counter clockwise (everyone says towards the block and that confuses the heck outta me)
And about how much in general to get it close.... quarter turn.. half.. just a touch ??
 
#92 ·
Standing on the passenger side of the jeep looking at the distributor.. do I need to rotate the distributor clock wise or counter clockwise (everyone says towards the block and that confuses the heck outta me)
And about how much in general to get it close.... quarter turn.. half.. just a touch ??
You need to get a timing light or find someone that has one.
 
#95 ·
No problem,
I can get a timing light. I just wanted to have it somewhat close before starting it up and running it. I'll go to the local auto store and check out the loaner.
It won't be off that much and should start up in the old position. Just don't run it long like that.
 
#96 ·
FYI for anyone doing this in the future, before starting the bypass adjust the timeing to 8' btdc. thats what i did and it started right up after doing the bypass. I still had problems keeping it running until I dialed in the carb but it only took a matter of minutes before she was purring like a kitten!
 
#97 ·
You should recheck it now, it should have jumped when the computer was taken out.
 
#99 ·
why didn't I set timing first..

DOH !!!

Now you tell me !!!

... I am just about done.. I figured I had had enough for the night and will finish it tommorrow.. I purchased a timing light so it shouldn't be too much more tommorrow to finish up. I went ahead and removed all of the purge valve system as well. I had a few extra stuff to remove with the cruise control above the washer and coolant tanks. But was no biggie. I went ahead and took off a ton of vaccum crap and removed the purge air system as well.

The only thing I feel like I am not certain on doing right was resetting the carb mixture screws.... I decided to try it at one and a half turns out from all the way seated.. should this be close to first start it.. or do I need to loosen them another turn?

Thanks guys...
I guess I will find out how well I did tommorrow evening.
 
#100 ·
The only thing I feel like I am not certain on doing right was resetting the carb mixture screws.... I decided to try it at one and a half turns out from all the way seated.. should this be close to first start it.. or do I need to loosen them another turn?

Thanks guys...
I guess I will find out how well I did tommorrow evening.
All carbs and engines set up different for the mix, you will need to fine tune it.

I start at 5 turns out on both screws 'with' the stepper motor pins set as mentioned earlier, with their shoulder 1/8" from the back wall.

Once running, I get the timing set, then I fine tune the mix for 'best lean idle'.

To do that I start screwing the pins in, in 1/4 turn stages each, then give it a rev to set the flow, the turn them another 1/4 turn then give it a rev to set the flow, then.... until that last 1/4 turn starts a stumble happening. At that point, I back them off about 1/4 to 1/8 a turn.

I 'will' have to reset the idle speed usually more than once to keep it under 700 rpm while doing this.
 
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