So I have a good motor I pulled out of a 99 WJ and I put it into a 2000 WJ. After the swap it will not start. It sometimes kind of starts and sounds awful and backfires a bunch. Is the flexplate the same on both or should I have swapped that over as well? It did fight me lining up the motor and the bell housing so could I still have something off that would cause this? Any other possible suggestions?

I did the same thing last year on a 97 motor in a 98 XJ and everything fired up fine so I'm confused what is going on.

 

Well I repulled the motor and changed over the flex plate from the 2k to the 99 motor. Put it back in and same thing. Motor turns over but sounds like its out of time somehow. I did not mess with anything timing related so not sure how that would have happened. Thinking of swapping ECU's next. not sure what that would do here but I'm kinda lost on what to check next.

 

Well after more messing around with it and changing out the ECU with no change I figured I would pull the coil pack and I noticed that the connector was facing down on this one and on the original motor it was facing up. I ended up swapping the coil pack out and it fired right up.