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Discussion Starter · #1 ·
Hello all.

I am looking for some wiring help on my daughters YJ.

History:-
It's a 1989 Wrangler 4.2. Was automatic but we converted to AX15 a few years back, changed driveshafts, pedal box and axles to get appropriate final drive for 33" tires. Removed Carter carburetor and replaced it with a Spanish Weber.

Anyhooo, not sure why but the block developed a crack that was leaking coolant under the manifolds. May have frozen, not sure. But it cracked.

So I bought a complete 4.0 with engine wiring harness, injectors, manifolds, headers and ECU from a running 1999 Cherokee.

I have fitted the correct pilot bearing, moved the flywheel and clutch over, changed the water pump to YJ model and re-fabricated the exhaust to match the new layout. I have an external pump to get the fuel up to EFI pressure. The pump is powered through an oil pressure switch with a cranking over-ride to get fuel while starting.

Now with the 4.0 installed I just need to identify the wires that I need to supply with power to start and run the engine. Tach and other instruments would be nice too, but for now running the engine is the goal.

Problem:-
Can anyone tell me where to get a good schematic or diagram, or alternatively identify the connector and pins that I need please? I am sure I am not the first person to do this swap and hopefully some kind soul can save me a bunch of research and eye-strain. I tried searching the forum but didn't come up with anything I could use.

Thanks in advance.
 

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:welcome: to the Forum..:wavey:
 

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Welcome to the Forum Flatspin631,

Find a post by Got it at last. In his signature there's a free link to several Factory Service manuals and a couple Factory Parts Manuals.
Open that link and click on the manual that matches your YJ.

You'll also need a Factory Service Manual or a Chilton's manual for the '99 Cherokee (XJ). With both manuals you should be able to figure our which wires to connect to where.

It seems the easiest thing to do is to mount the XJ ECU to the right fender apron and abandon the YJ ECU (or remove it entirely). Use all the emission controls and running controls from the XJ.
Then follow the power connections for the XJ ECU to where the YJ ECU was originally connected.
You should be able to use all the YJ sensors for oil pressure and engine temp. The XJ intake manifold might not have the opening for the temp sensor, but you might be able to drill & tap the intake manifold if it has a boss where a temp sensor might go.

Other posters that have actually done this might have more and better advice.

Good Luck, L.M.
 
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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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YJ Manuals below, Sorry I don't have the 99 xj, but you could try using the '95, it has the yj and xj and it should be relatively close if not exact.


Good Luck!
 
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I'm in the middle of this swap now, but I abandoned the entire wiring harness from the 89 and ditched the renix system. This required the engine harness, dash harness, the body harness for rear lights and hardtop wiring, new gauge bezel, and new instrument panel. It was a lot of work, but all of my gauges work and there was no guessing as to what it what. Check this vid...

 

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Discussion Starter · #6 ·
Thank you everyone. Since we did the Nutter Bypass some time ago to try and get the Carter working acceptably I had already stripped all the extra wiring from the engine bay and got down to a single wire HEI distributor so all I really need to identify is the Start, Start/Run and tach which I am sure I can now do with the manuals (Thank you Got It at Last). I'll probably try and find the temp, volts and oil pressure as well and splice them into the bulkhead connector.
I'm going to try and set up my GoPro and if I get anything watchable I'll post it on YouTube.

Regards,
 

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The manuals will get you there. There are two big red and one big yellow wire coming out of the fuse box. Those should be all you need . 12V constant, 12V switched, and Crank I believe. The Tach i think is purple.
 
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