4.0L Swap Questions....anyhelp please! - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 04-09-2002, 12:54 PM
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4.0L Swap Questions....anyhelp please!

Gettin' the fever bad, it has been down a year now and I'm almost done. I'm trying to find any information on the wiring harness...everyone says get the wiring harness from donor but don't say how to wire it up with the CJ wiring....any help or info or sources would be great.... wiring would be better if I didn't have to spend $400 on a harness...I know that's cheap but I could buy other stuff with 4bills....
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post #2 of (permalink) Old 04-09-2002, 05:32 PM
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Re: 4.0L Swap Questions....anyhelp please!

Well you raise the same question I have been raising.

What I have done so far is to get the engine compartment harness from the donor vehicle.

I have tracked down two schematics - one for the 85 CJ and the other for the 95 Wrangler. I also found a link to a schematic on this board that identifies where the color-coded wiring goes from the PCM at least on a 94 model.

What I understand so far is that one needs:

1. The fuel injection rail and intake manifold with throttle-body.
2. The throttle-cable from donor vehicle.
3. The charcoal canister from donor vehicle.
4. Engine engine compartment wiring harness from donor.
5. Thermostat housing from donor with temperature sensor from donor.
6. Exhaust manifold with oxygen sensor from donor or will need to put one in the exhaust.
7. MAP sensor.
8. Speed sensor - I am uncertain about this one. At one point I understood it connected in someway to the speedo in the tranny.
9. After-market harmonic balancer/sensor unit for use with 258 -substitute for sensor mounted in the Tranny on the 95.
10. Distributor from donor vehicle.
11. Maybe another temperature sensor (based on webnotes, cut uncertain about where it goes yet or if it is needed)
12. I also believe there may be an airflow sensor, but uncertain about this one yet.

The donor vehicle was a serpentine system - so it means changing the pulleys on the alternator, power steering, and crank (I believe).

Web notes recommend stripping the covering off the wiring harnessness and laying it out on a table. Then tracking the wiring that will be needed. I understand the remainder of the wiring is not needed and can be removed. I have not yet done this part as I am still trying to finalize what is specifically needed. I will probably not remove any of the wiring until such time as the vehicle is actually running. Then with that reassurance, I will be more confident in cutting.
post #3 of (permalink) Old 04-09-2002, 06:38 PM
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Re: 4.0L Swap Questions....anyhelp please!

Don't try to put the two harness together! Gut out all of your old stuff that isn't needed and wire the engine side seperate, with brake outs for:

1) Fuel pump out
2) check engine light
3) keep alive memory (always hot)
4) momentary start (power from start solenoid)
5) key on power
6) common grounds to battery
7) brake input (needed if using auto for idle quality)
8) a/c input (allows higher idles if wired to a 12V switch)
9) control for electric fan

A radio store usually sells a nice junction block for making these connections.
I find it easier if you clamp the 60 pin connector in a vise, and get an ohm meter for tracing your connections. The power distribution center isn't necessary, however it makes it nice for both the ASD relay and fuel pump relays. I also like using the serpentine belt drive from the 4.0 and hooking up the alternator, as the PCM has the ability of controlling the field and it used special zenior diodes for protection.

Where in Colorado do you live? I might be able to give you a hand.

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post #4 of (permalink) Old 04-09-2002, 07:58 PM
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Re: 4.0L Swap Questions....anyhelp please!

That extra sensor is calle a MAT (manifold air temp) It threads into the top of the mainifold behind the throttle body. You also need a computer form a '91-95 and, if you are running an automatic, you need a cable for the kick down linkage. The speed sensor is a device that bolts on the trans case where the spedo cable comes out. Unscrew the cable, place in this device, and screw the cable back into the other end. It has a 3 (?) prong connector that sends pulses up to the computer. I know HESCO sells these sensors. This will alow the computer to read the pulses, and your spedo gauge to still read. I've almost got my MPI/4.0 head conversion compleated and so far this is what I have learned.
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