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Wiring for dummies ...

Blatant

NAXJA Forum User
Location
Phoenix
or those who've never done it beyond wiring lights.

I'm swapping a 2003 4.3 Vortec and 4l60e into my 86 XJ, at least in theory. I'm dealing with the fact that I'm going to need either a Howell or Painless harness and a reflashed 'puter in order to make this work (the stock 4.3 harness is montrous).

Where I need some real tech help is understanding how the drivetrain (underhood) wiring interacts with the internal wiring (instruments, lights, AC, stereo, etc.).

Since the old drivetrain is gone, I can simply remove all the original underhood wiring, correct? Where do I do so? Where it terminates through the firewall?

And is it easier to do away with some or all of the internal wiring and dash as well? How do I know what goes and what stays? I could just build a flat dash and put in new guages, would that be simpler to wire?

The rig has a rat's nest behind the dash and it's pretty confusing. Any help or links to more info would be much appreciated.
dion
 
Blatant said:
or those who've never done it beyond wiring lights.

I'm swapping a 2003 4.3 Vortec and 4l60e into my 86 XJ, at least in theory. I'm dealing with the fact that I'm going to need either a Howell or Painless harness and a reflashed 'puter in order to make this work (the stock 4.3 harness is montrous).

Where I need some real tech help is understanding how the drivetrain (underhood) wiring interacts with the internal wiring (instruments, lights, AC, stereo, etc.).

Since the old drivetrain is gone, I can simply remove all the original underhood wiring, correct? Where do I do so? Where it terminates through the firewall?

And is it easier to do away with some or all of the internal wiring and dash as well? How do I know what goes and what stays? I could just build a flat dash and put in new guages, would that be simpler to wire?

The rig has a rat's nest behind the dash and it's pretty confusing. Any help or links to more info would be much appreciated.
dion


If it were me, I'd pull everything out and redo it all. Who knows if you'll be able to get the stock gauges to work with a computer from a different engine. I guess you'd have to get advise from the guys that have actually done it. Since you already have to get rid of the engine and computer wiring though... what's that leave? Stereo and gauges?
Billy
 
The instruments in an '86 XJ have no interface with the computer. In '86, the 4-cyl had a computer controlled carburetor and the V-6 had no computer at all. All you need for the gauges is to connect the correct wires to the sensors in/on the engine.

I'd suggest just getting a wiring diagram. I believe both the Haynes and Chiltons Cherokee repair manuals have wiring diagrams that will cover your year. It should not be necessary to rip out the wiring under the dash.
 
Bumping this up. I went through my manual this weekend. It did have engine and chassis diagrams for my model (86, originally 2.8/auto), though I'm still not clear on a couple of points. Particularly, how the engine bay wiring interacts (if at all) with the interior harness (guages, lights, etc.).

Input?

Can I pull the underhood harness and leave the interior harness? How do I separate them?
dion
 
There is almost nothing under the hood that interfaces with the dash wiring. Your wiring diagram will show you what does.

The connections you'll need are:

One wire from the temperature sensor to the temp gauge (and this may be an open question. The early XJs used one temp sender for the gauge and a separate one for the ECU. Later XJs used a single sender, and the gauge pulls data from the ECU. Dunno how the Vortec was set up, but there should be a plug somewhere in the cooling system where you can screw in a stand-alone temp sender for the gauge)

One wire from the oil pressure sender to the gauge

Fuel gauge feed wire

Oh, yeah. The brake system combination valve has a wire that feeds to the warning light on the dashboard. Not engine-related, but it is under the hood.

A/c wiring if you have a/c
Voltmeter feed wire.
 
If you have a 2,5 there's just one fat cable running through the firewall to the under dash computer, very easy to pull out.

When it comes to gauges wiring: Anyone have any schematics for this? I have been trying to hook some gauges up for one and a half years now, found lots of diagrams but zilch on the gauges (trying to hook a 90+ cluster to a 93 ZJ 4,0)
 
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