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Unread 11-29-2013, 06:12 PM   #1
underpowered
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cut down 4.0 harness for buggy?

anyone on here ever cut down a 4.0 harness for use in a tube car/buggy?

looking as possibly building a full tube buggy in the near future and have always liked the 4.0. I think the inline would be pretty easy to package in a buggy backed by an aw4 and 231 would give me a decent drivetrain and allow me to keep it light as well but i have no need for much of the wiring.

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Unread 11-30-2013, 06:36 AM   #2
jsawduste
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OBD1 or 2 ?

You are keeping the FI, right ?
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Unread 11-30-2013, 07:58 AM   #3
underpowered
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yes. keep the FI.

i already have an OBD I setup i could use, but this is all planning currently so i could pick up and OBD II setup if need be as i don't have the engine yet, so i don't know what year it will come out of.
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Unread 11-30-2013, 01:22 PM   #4
jason m
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Take this with a grain of salt, don't cut to much off. I have built and helped build ( including mine ) maybe 6 Jeep based buggys off the 4.0 motor.
I have over each build eliminated a little more wires each time only to go to far on a friends buggy and after two years after it being done, another complete motor swap along with a new harness we still cant get it to run right.

I had a friend help with my harness and all he and I did was while it was running cut the non essential and then just bundled up under whats left of my dash.
That's how I do them all now, over the summer I helped get another good friends rig running and he cut way to much off and we just figured we could just re-connected what he cut, wrong to much of a mess.
So he was forced to buy a inside cab wiring harness and did what I did bunch and tuck the wires under his little dash.

Jason.
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1993 YJ 4.0 60 Front, Rear steer 60, bolth spooled, 5.38's, 700r/241 39.5 iroks and beating it like it owes me money.

And on the 8th day, God created the 14 bolt....
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Unread 11-30-2013, 02:39 PM   #5
jsawduste
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Before you do anything come up with a plan for the whole vehicle.

OBD1 is a lot more forgiving then OBD2 with only a few sensors and minimal inputs. While OBD2 has a lot more to contend with such as extra O2 sensors, battery temp sensor, gauges that run off the ECM etc. While some of this can be cal-ed out there is still a lot of complexity by comparison. There is the ability to reflash the OBD2 ECM so if that is something you might want to do then OBD2 is a strong contender.

The industry is just now starting to be able to reflash some OBD1 ECM`s by replacing the Eprom. This new ability is still fairly new but it can be done.

For most naturally aspirated 4.0`s OBD1 is good enough even with a few engine mods or even a stroker.

You need to make a plan. How are you going to control fuel, spark, ignition, charging, lighting and so on. Study up the wiring harness and see were you can go.

Use my OBD1 YJ stroker as an example. A simplified example but hopefully enough for you to get planning.

Engine management is stock. Did add a few grounds but am using the factory PDC as my primary power/switchbox. Was able to cut away things like AC, underhood light, diagnostic connector, PS input but that was about it. Within the PDC I was able to add relays to control lighting and such by utilizing the relay sockets that were for options like ABS, AC etc.

Front lighting is another harness. Here the bulkhead was opened up and new wires were ran to control the lighting, washer pump etc. Remember the new relays in the PDC ? These added circuits now became part of the front harness. The bulkhead uses GM Metri Pack terminals in 280, 480 and 620 sizes so it was easy to add or subtract wiring.

The dash harness is a combination of all. Here is where you need to really look and see what you want, how your going to run it and can the factory harness support your desires. Example would be the ignition switch on the column. Why change it ? It works well enough as is. Primary lighting is controlled by the factory on off switch and the hi/low beam switch. The dash dimmer was tossed. Interior lights are on there own circuit that is controlled by a rocker switch. Extra lighting or fans are controlled by the dash mounted switches so these circuits are add on`s that combine the engine, dash and front lighting. Gauges are hard wired to the senders.

There is plenty more but I think you get the idea that you want to look at the wiring as a whole not as a single entity.

I like to get 1x8x6`s and use the zip ties that have provisions for a screw. Layout the harness(es)/components and loosely tie them down with the zip ties. This way you can follow each wire, add or subtract as needed.

A good VOM a wiring diagram and a plan is all you need.
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Unread 11-30-2013, 05:06 PM   #6
underpowered
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ideally, i would prefer to make the engine stand alone and not connected to any other systems in the vehicle. This is mainly because i won't be using anything else from the jeep that requires electronics. headlights will be on a simple toggle, gauges will be mostly mechanical for Oil pressure, tach, temp, and volts are all i will really need and each of those are independent to the wiring. Tranny will be full manual control aw4 so no need for PCM signal for it either.


mainly in the current stage i am trying to decide if the 4.0 will be worth it. Other options are GM engine, and many of those i can simply buy a pre made stand alone engine harness that is plug n play. the simpler the system the better and i know teh 4.0's are not overly complicated. Considering a GM TBI setup as well as those are easy to work with. LS based GM would be wonderful and i can get a stand alone setup but things get pricey.

I think the 4.0 and its inline setup will be easier to package in the buggy than a V8 will be which is one reason i am really considering it and i believe even in near stock form it will propel a buggy nicely.
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2000 powerjoke tow pig

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Unread 11-30-2013, 06:50 PM   #7
jason m
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A V-8 GM motor buy far is a easier to package into a buggy than the 4.0. The 4.0 is tall and loooong.

But nothing beats the fact that a 4.0 can run sideways and for the most part upside down, ask me mine did. Your not going to find a more robust motor outside of the Mopar slant 6Cyl.

Like I said don't go ham cutting the harness up, ive done GM 4.3/350 TBI set-ups on stand alone and there are buy far easier than a 4.0 for whatever reason.

I'm down to a push button start, a toggle for the fuel and a toggle to the CPS, the rest of the BS along with the PC are zipped tied into a neat little ball and tucked up under whats left of my dash.

Jason.
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1993 YJ 4.0 60 Front, Rear steer 60, bolth spooled, 5.38's, 700r/241 39.5 iroks and beating it like it owes me money.

And on the 8th day, God created the 14 bolt....
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Unread 11-30-2013, 07:24 PM   #8
underpowered
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the 4.0 has proven to be one of the most reliable engines i have ever owned. I have never seen a stock engine take such abuse and never even bat an eye.

i plan on doing all my research before i just start hacking at the harness. i want to know it will work before i even begin. figure out what i do and do not need. that is the beauty of the internet, and chances are good someone has done it before and can offer advice on it.

currently i have a 92 XJ that could serve as a donor harness, and with a motor rebuild even the motor.
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2000 powerjoke tow pig

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Unread 12-02-2013, 07:32 AM   #9
ltrail
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My 350 tbi harness is getting cut down again to bare minimum for my xj buggy. The 4.0 would be solid also. I am finishing a 4.7 stroker for my new dd. Shop around would be my advice if you don't have an engine as of now. Just swapped a 5.3 in boss's sons 76 Chevy. Around here you can get ls based engines with cut harness (5wire hookup) for around $2500 for carb and $3500 for efi.
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Unread 12-02-2013, 05:46 PM   #10
underpowered
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Quote:
Originally Posted by ltrail View Post
My 350 tbi harness is getting cut down again to bare minimum for my xj buggy. The 4.0 would be solid also. I am finishing a 4.7 stroker for my new dd. Shop around would be my advice if you don't have an engine as of now. Just swapped a 5.3 in boss's sons 76 Chevy. Around here you can get ls based engines with cut harness (5wire hookup) for around $2500 for carb and $3500 for efi.

i plan on having less than that amount in the entire drivetrain. let alone just the engine.

Heck, you can buy a complete 5.3 for around $500, then a stand alone harness is only about $600 for an LS based engine.
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2000 powerjoke tow pig

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Unread 12-08-2013, 09:09 AM   #11
ltrail
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Sounds like a deal! Don't have that good of prices out here.
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