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lilmick21602 05-06-2013 02:37 PM

Yj 2.5 - 4.0 swap
4 Attachment(s)
Hey, was wondering if anyone has done this? I know there are several members that mention it and give info. I have a few questions as to where I need to go next. Just to catch you up to speed I have a thread that shows my YJ build.

Here is the deal:

1st: The frame engine pcm all harnesses are from 91 YJ 4.0.
The body is a 94 YJ that had a 2.5.
Speedometer and gauges?????
Question; the speedo from the 91 has not only and electrical plug but a manual speedometer cable that comes from the tail of the transfer case the would connect to the speedometer if it was a 91 body with 4.0. But my 94 2.5 (body) speedometer does not have this type of hook up. What to do? change the interior gauges or can the gear be changed out of my transfer case of the 2.5 to the 91 transfer case?

2nd: The fuel tank and pump that I am using did come from the 94 2.5 YJ. I was wondering first if the 4.0 could use this pump considering the fuel pressure??? And second I have been trying to figure out how to hook the pump up. The wiring harness for the 91 is different than the 94. Was wondering where the fuel pump wires came from and would I have to hard wire them to the 94 2.5 fuel pump???

I have two manuals and using google but they don't show everything.

Also, I am looking @ what I believe is the Balast Bypass Relay. My book says this is only in XJs not YJ. Go figure...

Here are some Pics.

lilmick21602 05-07-2013 03:23 PM

Figured out how to eliminate the fuel pump issue. I ordered a wiring harness for a 91 jeep that had the fuel sending unit wiring on the tub harness. I also ordered a Chilton Haynes manual that will clarify an issue. The manuals I have are for 92 and 93 jeeps. I found out that the 91 is different in that the gauges are not electronic. So I hope to eliminate that issue with the new tub wiring. Still trying to find out what two wire splices are coming off the balast??? Wires are Dark Blue and Black. and there are two different splices with a lot of slack wodering where they go???

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