RedBullMJ Posted March 28, 2008 Posted March 28, 2008 OK boy and girls, this is the deal: About a year ago I built up a really nice 89 MJ, 4.0 Auto 4x4 on 35inch MTZs......I sold it and regret it! So, I bought a 89 2.5 2wd short box. My plan was to drive the wheels off of it as a daily driver.......but I got all itchy and want to convert it to 4x4. I picked up a wrecked 2000 TJ, 4.0 3550 D44 and I want to swap it ALL over to the MJ.....drivetrain, computer, harness and everything. the basic swap is easy but my questions are as follows: Is swaping electronics straightforward? any computer issues? Are the 4.0 and 2.5 motor mounts in the same place? Any fuel issues with the factory comanche tank and pump? Any other advice you can give me? You guys have done some great projects and I hope to learn some tricks from you!! timmyk
mvusse Posted March 28, 2008 Posted March 28, 2008 Correct me if I'm wrong as the only first hand experience I have is with a 4.0 Renix, but I believe the 2.5 has throttle body injection, whereas the 4.0 has multi port. And I believe multi port injection needs much higher pressure, hence a different pump.
Kenosha Warrior Posted March 28, 2008 Posted March 28, 2008 helluva undertaking but its doable. The Mounts, IIRC, are in the same spots. I'm thinking 2.5 Renix to 4.0 Renix, not 2.5 Renix to 4.0 Chryco so I'm not 100%
RedBullMJ Posted March 28, 2008 Author Posted March 28, 2008 Correct me if I'm wrong as the only first hand experience I have is with a 4.0 Renix, but I believe the 2.5 has throttle body injection, whereas the 4.0 has multi port. And I believe multi port injection needs much higher pressure, hence a different pump. I am going to use the TJ fuel system, tank ect....
mjeff87 Posted March 28, 2008 Posted March 28, 2008 the motor mounts are the same, but the frame horns they attach to are different. You'll need a set of 4.0 XJ frame horns (they bolt on, not welded) Jeff
RedBullMJ Posted March 28, 2008 Author Posted March 28, 2008 the motor mounts are the same, but the frame horns they attach to are different. You'll need a set of 4.0 XJ frame horns (they bolt on, not welded) Jeff Thanks, thats the info I need, I will pick up a set at the junk yard....they have about 1000 old 4.0 XJs.
RedBullMJ Posted March 28, 2008 Author Posted March 28, 2008 Correct me if I'm wrong as the only first hand experience I have is with a 4.0 Renix, but I believe the 2.5 has throttle body injection, whereas the 4.0 has multi port. And I believe multi port injection needs much higher pressure, hence a different pump. Will a late model XJ pump work with the 2.5 gas tank? I would rather use an new style XJ tank/pump system.....
Motion Offroad Posted March 28, 2008 Posted March 28, 2008 XJ and MJ gas tanks are different. Also the pumps are different as well. Just get a MJ 4.0L pump and it should fit into your 2.5L MJ tank.
mjeff87 Posted March 28, 2008 Posted March 28, 2008 4.0 pumps have a fuel pump outlet check valve which holds fuel pressure when not running, but the 2.5 pump does not. I'd assume the 2.5 pump would deliver enough pressure to run, but restarts might be a problem. Jeff
HOrnbrod Posted March 28, 2008 Posted March 28, 2008 4.0 pumps have a fuel pump outlet check valve which holds fuel pressure when not running, but the 2.5 pump does not. I'd assume the 2.5 pump would deliver enough pressure to run, but restarts might be a problem. Jeff That's an easy fix. Just install an inline check valve in the supply line like the below. I've done this with other FI vehicles and it works well.
RedBullMJ Posted March 31, 2008 Author Posted March 31, 2008 the motor mounts are the same, but the frame horns they attach to are different. You'll need a set of 4.0 XJ frame horns (they bolt on, not welded) Jeff I bought the 4.0 frame horns from the junk yard......they were definitely different. Any other suggestions out there?
pingpong Posted March 31, 2008 Posted March 31, 2008 the motor mounts are the same, but the frame horns they attach to are different. You'll need a set of 4.0 XJ frame horns (they bolt on, not welded) Jeff I bought the 4.0 frame horns from the junk yard......they were definitely different. Any other suggestions out there? Jeff knows.. cause he picked the mounts up from my parts dept. For the fuel pump... MSD makes a pump that works great with the 4.0.. just install a fuel cell and call it good and run an inline pump.
RedBullMJ Posted March 31, 2008 Author Posted March 31, 2008 the motor mounts are the same, but the frame horns they attach to are different. You'll need a set of 4.0 XJ frame horns (they bolt on, not welded) Jeff I bought the 4.0 frame horns from the junk yard......they were definitely different. Any other suggestions out there? Jeff knows.. cause he picked the mounts up from my parts dept. For the fuel pump... MSD makes a pump that works great with the 4.0.. just install a fuel cell and call it good and run an inline pump. If I need to install a fuel cell..................I will install the TJ tank and pump in the bed or underneath somehow.....
RedBullMJ Posted April 1, 2008 Author Posted April 1, 2008 XJ and MJ gas tanks are different. Also the pumps are different as well. Just get a MJ 4.0L pump and it should fit into your 2.5L MJ tank. I am going to try this first....good idea to try. I also picked up a few interior lights and a MJ D44 from the junk yard.........very odd but the junk yard had two MJs, one 4cyl/2wd and one 4.0/2wd (maybe metric ton)...both short beds. Thanks for the advice everyone.....ComancheClub is a great help.
reson46 Posted April 1, 2008 Posted April 1, 2008 Good to see you here Timmy! :clapping: I can't wait to see how this turns out. I'm sure it will be incredible. I'll watch this and help out any way I can. Willy
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