YJ Build: to OBD-II or not to OBD-II?

[Root Moose]

I'm getting things together for this winter's YJ build.

I've been watching the want ads for a Cherokee to donate the engine, transmission and transfer case (4.0/AW4/NV2xx).

It seems like there are a number of good deals in this area for a 1997-2001 XJ donor.

Any real reason I should avoid OBD-II? The electrical wiring and computers doesn't bother me. I'm more wondering about getting the original YJ dash gauges (or aftermarket replacements) working and the general suitability of the newer drivetrain to a YJ.

I think the transfer case needs to be swapped to a mechanical speedometer style pickup. And the rest of the gauges? Nothing funky there, right?

I have to use the XJ fuel tank? Can I make the YJ fuel gauge work with it?

TIA

 

[Go4Lo]

Root,

Not sure if this helps or not, but I just finished building my MJ in June using a '99 XJ as the donor vehicle. I transplanted all wiring under the hood and inside the cab over from the XJ and trashed the MJ harness. During the process I had the 4.0L from the XJ built into a 4.7L Stroker. I kept the OBD II system in tact from the XJ and so far the truck is running great and no CELs. I prefer the OBDII system over the OBDI system because I feel like it's more user friendly when it comes to reading codes and trouble shooting.

My largest hurdle was the fuel system, more specifically adapting the XJ fuel pump to work with the MJ. The easy fix would have been a fuel cell but I really didn't want a fuel cell in the bed of the truck so I ended up converting the existing MJ fuel tank to run the XJ pump assembly by using a set of fuel cell rings and cutting a hole in the top of the tank. You may be able to do something like this on the YJ tank.

Long and short of it is I would keep all the wiring intact if possible.

Sounds like fun project!

:smiley_drive:

 

[alosix]

Is this a road going rig and what are your emissions requirements like up there eh?

If you're not afraid of the wires, the ODBII stuff and newer 4.0ls aren't bad to work with, and definitely make more power than their Renix or carb counterparts.

If I were doing one in CA, going from a non ODBII engine to an ODBII engine would likely cause me to make sure everything worked and I had all of the necessary emissions bits to keep the CELs away before I could pass smog with it.

 

[Root Moose]

Oh man, the original plan was to do a late model drivetrain swap into the MJ this winter, including the modern dash and front clip, doors, etc. but my boys (5YO and 8YO) really want the YJ done so we can go "real froading". LOL They're only young once...

Thanks for the tip on the fuel system. That sounds very workable. Was there anything funky you had to do with the rest of the instrumentation? My YJ is a 1987 so I guess the instrumentation is more or less the same as on a MJ.

This will be a road vehicle, built in the expedition style more so than a 4x4 trail **********. Nowadays I guess that means mild lift and 33s. I'm going to coil the front end for ride quality.

The Jeep is a 1987 which means that I have carte blache with respect to emissions (1987 and older is exempt from testing or visual inspection in Ontario). Being a responsible person I intend to keep all emissions controls working... it's a function of picking what setup makes sense I guess. OBD-II sounds pretty workable at this point.

 

[alosix]

The Jeep is a 1987 which means that I have carte blache with respect to emissions (1987 and older is exempt from testing or visual inspection in Ontario). Being a responsible person I intend to keep all emissions controls working... it's a function of picking what setup makes sense I guess. OBD-II sounds pretty workable at this point.

How hard is it to migrate to Canadia (that's where canadians come from right? )? :victory:

I think for a YJ, a 1995 should have everything needed to use the newer style engines (dash/gas tank/etc)..

Though.. if I was going through the work for a swap I'd probably look at something that's more powerful and more efficient. DCX 5.2s and 5.9s (even hemis aren't bad to swap), GM 4.3 or late model 350s go in pretty easy as well.

Jason

 

[Root Moose]

I actually just got rid of a GM SBC (Gen I) and 700R4 combo that I had acquired for a universal Jeep a number of years ago. I really can't be bothered with non-bolt-in stuff these days.

As for emigration, start here I guess (closest Consulate to you?)

http://www.canadainternational.gc.c...ervice_no-non.aspx?lang=eng&menu_id=13&menu=L

Click on L.A.

I'm in Ontario in an emissions zone. If I was about 20 minutes west more rural I wouldn't need to worry about emissions testing for any of my vehicles. They only test areas with a high enough population density to merit caring.

 

[Root Moose]

Oh, and now that you mention the newer Jeeps and the fuel tank... you've jogged an old memory. I have an old parts YJ I picked up that had a TJ tank and sender swapped into it at some point. I'm guessing that will work...

 

[Go4Lo]

Food for thought....a couple of pics of my MJ/XJ tank set up for you. :victory:

I transplanted the interior including the dash and all gauges from the XJ to the MJ cab so I'm not much help on adapting the YJ gauges to the later model wiring harness.

MJ interior post swap

 

[Root Moose]

Excellent! Thanks a bunch!

I don't suppose you have any pictures of the little tabs/mounts or whatever they are called where the dash bolts to the cowl?

I've read a a number of build ups on doing this swap but haven't seen what is required to get the dash on the cowl. I'm guessing it is straightforward since no seems to bother with documenting it?

 

[wipeout]

Food for thought....a couple of pics of my MJ/XJ tank set up for you. :victory:


I transplanted the interior including the dash and all gauges from the XJ to the MJ cab so I'm not much help on adapting the YJ gauges to the later model wiring harness.

MJ interior post swap

That looks really great. Just curious what radio/nav head unit you have installed in there?

 

[Go4Lo]

Excellent! Thanks a bunch!

I don't suppose you have any pictures of the little tabs/mounts or whatever they are called where the dash bolts to the cowl?

I've read a a number of build ups on doing this swap but haven't seen what is required to get the dash on the cowl. I'm guessing it is straightforward since no seems to bother with documenting it?

I have ton of pictures from my build but for some reason I don't have any close ups of dash tabs. Like you I have seen many different ways of attaching the dash to the cowl. For my build I used a piece of 1" aluminum from Lowes to relocate the holes on the dash to match the holes on the MJ cowl.

I will forewarn you, NONE of the holes on the XJ dash line up with the MJ firewall/cowl. I removed all the MJ dash mount brackets and drilled all new holes for the XJ brackets.

This will become your best friend for removing the MJ brackets.

Mock up of the XJ subframe in the MJ.

All new holes to be drilled

I have many more pics of the dash swap if you need them just let me know. I'm sorry I have completely hi-jacked your YJ thread with MJ pics....

 

[Root Moose]

I'm sorry I have completely hi-jacked your YJ thread with MJ pics....

Don't sweat it - as long as we are talking about somewhat more involved stuff than Jeep bolt-in mods it's all good as far as I'm concerned. Besides, I'd rather be building the MJ this winter but won't so this is somewhat therapeutic.

Just so I understand this correctly... those aluminum brackets get bolted into the MJ cowl and the XJ dash bolts to the brackets? The extra piece of aluminum you used was to help space or place the brackets properly?

 

[Root Moose]

Just to get a little more on track...

Why wouldn't I use a OBD-II drivetrain? What are the negatives compared to a YJ/XJ OBD-I drivetrain. (carburetor is not an option - hate them)

What about ZJ drivetrain? I doubt I'd do a 318/5.2 - not a fan of that engine.

 

[Go4Lo]

Don't sweat it - as long as we are talking about somewhat more involved stuff than Jeep bolt-in mods it's all good as far as I'm concerned. Besides, I'd rather be building the MJ this winter but won't so this is somewhat therapeutic.

Just so I understand this correctly... those aluminum brackets get bolted into the MJ cowl and the XJ dash bolts to the brackets? The extra piece of aluminum you used was to help space or place the brackets properly?

Yes, as pictured the 97+XJs use a cast aluminum sub frame that bolts to the lower "A" pillar/inner fender as well as to cowl at the top. The XJ firewall/cowl has brackets and studs that are used to locate and mount the top 2 bolts of the sub frame. This is not the case on the MJ, so I drilled holes straight through the cowl into the wiper motor comparment and used large fender washers to set the spacing.

I this pic you can see how the XJ firewall/cowl has the spacers and studs built in for the sub frame.

The aluminum strip I was referring too was used for the tabs that the actual dash uses to mount to the tabs that are on the MJ below the windshield.

 

[jeepdreamer]

Bring out the monkey...

Sorry to toss out the proverbial wrench toting tree swinger but I think there is one area you will need to address.
The Speedo/dash.
You will likely find it easier (maybe?) to just buy (craigslist/ebay/junkyard?) an entire, complete dash from a 9....uh, 3? or newer YJ. IIRC, the speedo was changed around 91-92 to a much different style. They look similar but don't interchange and IIRC the speedo interacts with the OBD system...? I may be off but I swear I delt something along those lines with my 91...