Nutter Bypass: Carter #2425 - No Stepper Motor - Jeep Wrangler Forum

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Old 06-29-2012, 10:57 AM
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Nutter Bypass: Carter #2425 - No Stepper Motor

I've been going nuts trying to figure out the Nutter Bypass on my Jeep. I'd always get completely stumped because not only does my Carb not have a stepper motor, the ports are set up differently - and the places the instructions said I should have ports, I didn't.

Bear with me... I know I can get long-winded, but I figure it's better to explain everything I can first thing rather than waste your guys' time asking me questions that I may already have the answers to. I would deeply appreciate any help I can get...

So I took my ipod out and took some pictures of my carb... I was able to get a picture of the passenger side of the carb by wiggling my ipod back there. I looked it up the model number and it appears my carb is a 1972 Dodge 318 2 barrel Carter Carb #2425...

Here's a picture of the stamp:
Attachment 136441

Here's one with a view of my carb from the drive's side fender:
Attachment 136442

... And a picture of the back of the carb - No stepper motor... Or place for one.
Attachment 136456

The first link of my google search was where I found out what my carb was, but interestingly enough the second link down in my google search was THIS

The guy has the same carb as me. He has a different model Jeep, 1986 CJ - I have a 1989 YJ, but I'd think it'd apply to me as well. He was asking he would go about how he would do the nutter bypass without a stepper motor.. If you don't want to go read it, I'll quote want appeared to be the "accepted" responses, the same guy said both quotes:

Without the original type carb there is all the reason to nutter the ignition. Likewise with most all of the sensors, switches and control devices. Otherwise the computer will not move beyond the open loop operation in the warm-up mode.
And when asked to clarify:

The OP has an '86 CJ, it was equipped with both the timing control computer as well as the stepper-pin BBD.

The topic is pertaining to the attempt to nutter the carb when in fact it is the ignition that is nuttered.

As yet we do not know if that has been done.

The latter generation(timing control)MCU has four modes of operation, Key-on, Start-up, warm-up, and cruise. Each of those modes operate in both open as well as closed loop.

When the original BBD w/stepper was removed and replaced with the BBD it causes the computer to continue to wait for predetermined priority input signals received from it's output signals.

No stepper pin adjustment= no O2 response signal to those changes= no mode change, same for the Idle relay, and the sol-vac. These devices had reaction to output signals... without them the computer stays in the warm-up loop.

I suppose that this is the mode of operation that is so often referred to on this forum as the "limp home mode"

There were 13 devices that gave or received computer signals...with the PCV solenoid being recalled that left 12. All are necessary as well as function properly so to move into the closed loop of the cruise mode.

As I mentioned in the earlier post the OP's carb has been mounted in place of the original so I suggested that the nutter bypass be performed.
So I guess we have our answer on if I SHOULD bypass... But now that raises some questions, and me being a psycho, thought about it all night at work and still can't stop thinking about it. Sorry if you're reading this yjman... I know I told/asked you the same things...

Now, I know for a fact that I don't have an O2 sensor in my exhaust because it was bad when we rebuilt my Jeep. My Dad said it wouldn't really matter that it wasn't there, and I never questioned him, so we just never replaced it. I don't even know if the wiring is still there. So I was thinking... Isn't that TWO (the carburetor (non-computer controlled) and O2 sensor(not there)) of the major players in the computer's timing and what-not of your engine?

You'd think it'd run really terribly if it was only getting information from the distributor... So do you think that I have a non-computer controlled distributor as well? So is my computer really doing much for my engine at this point? My engine doesn't run the best... But it runs good enough that I've never really had problems with it. No stalling, or dieing at stops. It idles a little high (around 1000-1300RPM) and it struggles at the recommended 800... I do get some misfires and sometimes it runs rougher than others.

I do have wires running from my distributor to the firewall. All of the wiring components are the same as the instructions I've looked up except for my Orange wire from the distributor connects to a green wire with black stripes at the ignition module instead of orange to orange.

Vacuum lines! Here's where I'm the most confused and haven't been able to find information on. Do I need to switch them up at all?

My distributor isn't hooked up to my carb at all at this point. Which according to all of the instructions I've seen, it's supposed to be. It's hooked up to the cylinder that sits next to the ignition module that has 4 vacuum lines running out of it - I don't know what it's called off the top of my head and I don't have a diagram in front of me... I've thought about trying to sort everything out via vacuum diagrams.. But I don't think they apply to me because I don't even have the ports described in the diagrams... Unless I'm missing something.

So after reading almost everything I can think of being relevant to the Nutter Bypass on my engine here's my questions:
CAN I do the Nutter Bypass? (the other guy suggested it be performed... But how?)
Do I just skip the stepper motor step?
Do I need to change any vacuum lines?
Is the computer even controlling the timing at this point? and..
Will I still need to adjust the timing if I do the Nutter bypass?

Thank you so much on advance! I'm so lost at this point...
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Old 06-29-2012, 07:47 PM
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Okay. So I was able to go out and check what exactly my distributor's vacuum line is connected to... After following it over the back of the engine it appears to connect to the "Purge Signal" (according to diagrams online) on that canister my the ignition module and coolant overflow tank. I can't seem to find any other vacuum lines coming out of my distributor, nor any other ports that I could hook another up to.

I found a list of the ports HERE
I got my distributor hooked up correctly to my carb now. The port it was supposed to be connected to was plugged. I also discovered that someone had plugged the line at where the purge signal is supposed to connect to the CTO valve. I unplugged it and connected it to the purge signal line leading from the canister.

My Jeep fired right up after I did this swap and idled at around 800RPM without struggling at all - normally it struggles at anything lower than 1000RPM. It also sounded smoother, but that might be just me imagining things.

I'm no mechanic... But I'm amazed my Jeep ran before with the lines so messed up. Does it make sense?

My "Heated air" port on my carb is currently plugged.
But I double checked everything else and it would appear everything it properly hooked up now - Vacuum line-wise...

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Old 07-05-2012, 07:07 PM
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Did it!

Alright, y'all! After no answers and lots of research... I decided to do it and see what happened.

I figured I'd do a follow-up so that if there were others in situations or with similar hardware as myself, they'd at least have a reference (refer to my first and second post if you don't know what I'm talking about).

Like I said in my previous post - I got all of my vacuum lines connected to my carb and distributor the way they were supposed to be. Then re-wired to bypass the computer. Initially I forgot to "splice into" to purple wire at the ignition module and just connected my "purple" wire to the one coming out of the ignition module. Then of course, orange to orange.

When I tried to start my engine it acted like I had a dead battery. So I hooked my charger up to my engine, and it fired right up. For some odd reason my timing light wouldn't flash and I figured I had a bad bulb or something, so I just tuned it by ear.

Here's a video of my first start after performing the bypass:


So then I tweaked it around a little more and still couldn't figure out why my Jeep was "dead" as I referred to in the video. I was mistaken in thikning it was my timing light. I went on to do a draw test with my volt meter and the highest draw I'd read was like 8 mA... NOT enough to kill my battery. So then I did a volt test on my battery and it was still at 12.66V (it was 12.66V when I bought it - I tested it right away) So there wasn't anything wrong there... Then I thought back to the instructions I'd read online and remember someone saying something about making sure you SPLICE INTO the purple wire, not just cut and connect.. So then I made a little 3-way connection and secured everything with electrical tape. Went back in my Jeep and turned the key - everything was normal again. I then turned it off, hooked up my timing light (just for kicks) and THAT worked as well!

I unplugged my distributor again, plugged the line and re-tuned my Jeep to 8* BTDC - I was actually only off my a couple of degrees from when I tuned it by ear... Not too bad for my first time ever tuning an engine, eh?

Here's a video of my Jeep running after it's 3rd start after fine tuning with the timing light (sorry, I think I drop a few swear words during this video... I was so excited my filter was turned off. Haha!) You can see my dog, Karmah, chillin' my the door in the beginning. :


So there y'all. If you have a pre-emissions carb, you can bypass your computer without changing any of the vacuum lines - other than when they are originally supposed to be for your carb. that is. Mine were all sorts of messed up from before I ever even tried anything. I got them all sorted out and I think it saved me from some headaches at the time of performing the bypass.

Also - when they say to be careful of the engine fan, they mean it. My finger got a little close to the fan and here's what happened it hurt at first - Now it's just numb. It flapped back maybe 1/4 inch at first, but I stuck it back down and made sure it stopped bleeding before I took the picture. Stitches are probably required, but I hate hospital visits.. Too expensive for something like this, IMO:

Attachment 138224

If anyone has any questions of comments, please feel free to ask. I can give information on what I've personally done, and would be willing to give any insight I can based off of my research in preparation for my bypass. If anyone has any corrections or suggestions for the work I've already done, please let me know as well. The purpose of doing this is to make my Jeep run as well as possible, so any suggestions to make it do so would be more than welcome.

Thanks for checking in, y'all!
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Old 07-06-2012, 07:58 AM   #4
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good work man. you learn fast. be careful with the fan and belts when running, ask me how I know, stay safe..Driller
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Old 07-08-2012, 04:42 AM
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Originally Posted by Driller View Post
good work man. you learn fast. be careful with the fan and belts when running, ask me how I know, stay safe..Driller
Haha! Did you get a little nibble from your fan too? Or did you get it worse than I did?

I think I got pretty lucky considering my finger made contact with a metal fan spinning at god-knows what speed. That's my luck though... ALWAYS get hurt - but somehow always manage to slip by good ol' mr. fatality...
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