How to - Nutter Bypass
Ok, for all those who want to perform the Nutter Bypass to eliminate the Electronic Control Module from your '83 and later CJ's and YJ's with 4.2L engines & BBD carb, here's the how to.
I know I had alot of questions before doing it about how to, etc. and I've seen alot of others asking questions, so I figured why not create this so hopefully most questions are answered. A little preparation on the front end saves alot of headache on the back end, right?
This is NOT a 'why should it be done' post, for that you should do other searches 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 alot of stop and go and even a little mudding.
Also, a BIG THANKS!! goes to Mike Romain who read over, corrected, and helped alot 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 at 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 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).
Re-routing wiring: Steps 3-11
Here is a link to a diagram of before and after wiring... http://home.sprynet.com/~dale02/ignmods.htm
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 (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 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 Ignition Module end to 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 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 step 4.
Step 8: Cut two lengths of extra 16 gauge wire to reach from ignition module to 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 on 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 orange at ignition module to orange from distributor.
Step 11: Attach your other extra length of 16 gauge wire from purple at ignition module to purple from 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 into 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.
Step 16: If using a timing light, follow instructions to hook it up. Should be like this: Clamp the pickup onto the #1 plug wire, then hookup the negative lead to the negative side of the battery, then the positive to positive on battery. Ensure no wires are in the way of fan, 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 mark up. 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 mark up.
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 ˝” bolt.
Step 23: Start the vehicle and re-check the timing. If it is off any, follow step 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!!
This is awesome...I wanted to do this while I was home to my new toy while I was on leave but didn't because I am not the smartest grunt in the world and I need pics. This thread will definately be saved for when I get home, and the madness will begin!!! Awesome post, and kudos to Mr Romain and the Arkansas Cheese Head!!!:thumbsup:
Great post. Awesome pictures and labeling.
not really part of Nutter, but I also recommend remounting the ignition module up high on the drivers side fender . It's much easier to work on, and it keeps the module cooler (and away from water).
Where do you pick up if you don't have the BBD? I already have a weber 34/34 installed.
Great post and very helpful pictures. It's an easy mod but I still wish I had this post to reference when I did mine. Great job man.
OK...this brings me to my total nOOb question...I wanted to do this mod while I was on R&R leave, but I was unsure where the Ignition module is, or even what it looks like. Now I have a pic, but is it stock located on the driver or passenger side fender (I don't have a windshield wiper bottle in the veh to reference)? If it is on the driver side, how hard is it to relocate to the passenger side?
And then there are some so lazy we don't even mount it back on the fender after testing a few modules. :)
It does keep it out of the salt spray though.
great job :thumbsup:. nice details and pictures.
The term Nutter Bypass is no more. We shall call it the "luckycheesehead bypass" from this point forward!
Very nice job on your write up. :thumbsup:
I appreciate all the great responses. I was hoping it would come in handy. I know I really could have used something like this when I did mine!!! Like I said, though, I can't thank Mike enough for taking the time to work with me on this. Got to give him credit too!
I just thought for sure that by the time it reached 200 hits, someone would say "oh, you forgot this or missed this" but I'm am overwhelmingly suprised that hasn't happened yet.
Seriously though, if anyone does find something missing or screwed up, let me know and I can edit it.
Are there any negatives to the nutter bypass?
Written the way John Nutter wrote it, it will also not pass emissions. Written the way luckycheesehead wrote it, it 'can' pass emissions.
The fact that it still passes the tailpipe emissions easily 'and' gets better mileage which is 'better' for the environment doesn't matter to 'some' emissions testers.
Here in Canada, every one I have done has passed emissions easily with numbers similar to mine: On the ASM 2525 test I got 589 NOx, 16 ppm HC and 0.11% CO.
Other than that, it just puts the engine in a 1981 or older state of tune, nothing else.
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