Nutter bypass question?

Stock FSJ Tech Area
Post Reply

Topic author
4XJeff
Posts: 9
Joined: Fri Feb 15, 2019 12:13 pm

Nutter bypass question?

Post by 4XJeff »

All,

Sorry if this is a stupid question but I'm ditching the factory carb and switching to a Motorcraft 2150. I thought I needed to do the nutter bypass? I have a 1982 cherokee with a 258, manual trans and the original carb does have the stepper motor on the back of it but I can't find the computer under the dash everyone talks about that gets bypassed. I'm attaching a pic that shows the only electronics I can find, it's all on the drivers side inner fender. I do have the orange and purple wires leaving the distributor but they are not twisted together and they look like they run into the silver box on the fender. Could I have a "stepper" carb but no computer? Not sure if I need to do anything or just forget the "nutter" and just put on the new carb?

Thanks!
IMG_2959.jpg
You do not have the required permissions to view the files attached to this post.
Current Jeep: 1982 Cherokee 258/4 speed
last Jeep: 1997 TJ
1st Jeep: 1986 CJ7
User avatar

Cecil14
Posts: 727
Joined: Mon Oct 01, 2012 6:40 am

Re: Nutter bypass question?

Post by Cecil14 »

Did you buy the truck new? If not, that vehicle is 37-38 years old now, likely someone has already pulled the computer. In any event, you only need to do the nutter bypass if you keep the BBD, to my knowledge the computer never had any control over the distributor (could be wrong there?). I would say just swap out the carb, tune things up, and see how she runs. If you still have problems, start troubleshooting then.

Edit: I need to correct myself, apparently the old computer did monkey with timing. According to here, the stepper motor was only found on '83+ CJs (I don't remember about our rigs, possibly earlier?): http://www.4x4wire.com/jeep/tech/electr ... gnition99/ so maybe you didn't have the computer to being with?

You should be able to trace your wiring down and ensure that the purple and orange go directly to the ignition module, that should ensure any computer stuff is out of the loop regardless.

Another option for ignition is an HEI distributor from a chevy 250 I6 with an AMC V8 drive gear. I ran that setup for a long time with an MC2100 and had great results.


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank
User avatar

brielly
Vendor
Posts: 43
Joined: Sat Oct 06, 2012 4:54 am

Re: Nutter bypass question?

Post by brielly »

Its been a long time, but as I recall my 83 had the computer under the dash but the 82 I have now never did. Rig it up and see how it runs.
82 Cherokee 258 w/ mopar fuel injection, ax-15
Fiberglass Rhino Grille reproductions for sale. See my post in the vendors section or contact me rrielly@verizon.net
User avatar

Stuka
Site Admin
Posts: 11789
Joined: Thu May 12, 2011 5:53 pm
Location: CA
Contact:

Re: Nutter bypass question?

Post by Stuka »

FSJ's don't have it under the dash (EDIT: Some years didn't?). Other Jeeps and AMC's did. The black box with the plug going into the top is the secondary ECU. And yes, it changes timing and adjusts the carburetor.

The bypass is the same as other vehicles, the wires are just in a different place.

I had done the bypass many, many years ago. But now I just run an HEI ignition, along with a Weber carb that I installed back in 2003 or so.
2017 JKU Rubicon
Pevious Jeeps: 1981 J10, 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ
User avatar

Cecil14
Posts: 727
Joined: Mon Oct 01, 2012 6:40 am

Re: Nutter bypass question?

Post by Cecil14 »

I know there was an ECU in my '83 up under the dash way back when, I pulled it out many moons ago. I do not recall there being a black box like pictured above on mine, but who knows what had been modified prior to me getting it.

I never bothered with the bypass, I went MC2100/HEI straight away.

aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank

Topic author
4XJeff
Posts: 9
Joined: Fri Feb 15, 2019 12:13 pm

Re: Nutter bypass question?

Post by 4XJeff »

I'll track the wires, I kind of got side tracked replacing the plastic valve cover with an aluminum one to stop the leak! LOL. also waiting on my carb to show up. thanks for the info. I wasn't sure what the two boxes were on the inner fender, but I figured if it had a stepper motor on the carb there had to be a computer somewhere to control it...
Current Jeep: 1982 Cherokee 258/4 speed
last Jeep: 1997 TJ
1st Jeep: 1986 CJ7
User avatar

Cecil14
Posts: 727
Joined: Mon Oct 01, 2012 6:40 am

Re: Nutter bypass question?

Post by Cecil14 »

The bottom left is the ignition module, top right is the ECU apparently, and the top left are just diagnostic ports that you'll never be able to use.


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank

Topic author
4XJeff
Posts: 9
Joined: Fri Feb 15, 2019 12:13 pm

Re: Nutter bypass question?

Post by 4XJeff »

Cecil14 wrote:The bottom left is the ignition module, top right is the ECU apparently, and the top left are just diagnostic ports that you'll never be able to use.


aa
So if I understand correctly, once I put on the 2150 carb and a one wire HEI the top right ECU won't do anything? Would I be able to remove it and all the connecting wires?
Current Jeep: 1982 Cherokee 258/4 speed
last Jeep: 1997 TJ
1st Jeep: 1986 CJ7
User avatar

Cecil14
Posts: 727
Joined: Mon Oct 01, 2012 6:40 am

Re: Nutter bypass question?

Post by Cecil14 »

To my knowledge, yes. That's basically what I did to mine ~18 years ago. Lots of stuff since then, but initially that was the setup.


aa
1983 J-10 - 4.6L(MPFI)/CS130D/Hydroboost/NV3550/D300/44/44/3.54/Disc-Disc/32s/42 gallon 'burb tank
Post Reply