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Discussion Starter #1
Hello,

I recently did a motor swap on my Jeep and have issues that I needs some help on that. I started with a 1991 yj 2.5 and swapped with a 97 tj 4.0 motor and transmission. I thought it was a 95 but it wasn't so I changed all the parts on the block to a 95 so I can still be without obd1. My main issues is I have a 93 computer for a 4.0. once I wired it all up to the best of my ability nothing happens. I out a toggle switch on the starter and I can start it and it fires right up however, when I turn key I have no power to ignition or to the fuel pump. My first thought was ECM but when I turn the key 3 times the cumputer will run codes(only 33 for no ac) now I know that doesn't mean it's not screwed up but it is getting power. Is there something small I could be missing with the years like the 91 not sending the right pins or something I know 91-95 is supposed to mostly be the same but it does always go wacky sometimes with those years.
 

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You need a switched ignition source, you probably used a wire that shuts off power while cranking. Easy mistake that I and others have made with swaps.
 

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I used this D5 for the ignition power on my engine swap. I would find the right bulkhead wire diagram for your jeep if it is a different bulkhead. Got it at last should have some diagrams in his signature.

 

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Discussion Starter #4
For the ignition I used right from the battery so it isn't that I don't think it's more that when I turn key the fuel pump doesn't turn on nor will it crank, so what your saying is still something to do to fix ? Or maybe something different, thank you for info everything else has gone smooth wiring is just not my thing.
 

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Discussion Starter #5
I used new harness for 4.0 so I just figured it would all line up when I had it all plugged in lol
 

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Discussion Starter #6
Last thought, so if I get a 1991 harness for my same year then all the pins should hypathetically be the same ?
 

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Unfortunately, I haven't done this exact swap myself so I don't know the 4.0l engine harness wires very well. Hopefully someone else has or you have some head scratching and figuring to do with a factory service manual.
 

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So, it will start and run if you activate the starter manually? Correct? If this is the case I would think the computer is fine and wired correctly. Your issue seems to simply be between the ignition switch and the starter. It would just be the small wire going to the starter from the ignition switch. If I remember correctly it should be green... I'm not positive on that though.
 

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Discussion Starter #10
No it will not continue to run I have to manual put fuel into the intake to have to go. So I still think it could be starter but I don't hear fuel pump prime at all either and I doesn't have a neutral safety switch or anything like that stopping it.
 

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I believe there are multiple power supplies going to the ECM. Just because the ECM has power to set a code doesn't mean everything in the ECM is powered.

I know its a pain but basically what you need to have is the wiring diagram for your 91 chassis, and the 94 ECM so that you can trace all of the relevant power and ground connections between the chassis and the ECM.
 

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Discussion Starter #15
Okay guys I need more help with swap...so I got the 1991 harness and it all plugs in however it didn't come with anything to hook up to alternator and the Jeep still won't turn over which I assume because it all the plug for alternator aren't hooked up and no spark is getting to the spark plugs. Is there a set up on how to hook this all up or buy a kit ? I have the art up off a 1995 harness but not sure how to wire it up if that was the case also how can I upload and image on here there is a bigger plug with blue on it that I'm not sure about on harness it wasn't on my 2.5 harness. Thank you
 
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