NEW JEEP NO RUN 2

I posted questions nearly a month ago about a 96 xj 4.0 auto. I bought from a friend who picked it up to fix an did not have time. After several days of diagnostic testing it came down to only one cylinder had "good" compression. I pulled the dead to find several cracks in the head, chunks of a piston and crack in the block. I then bought a used motor with 20,000 on a rebuilt. The donor was a 97 xj. At a glance they looked the same, but after installing, and trying to install torque converter bolts the flexplates were different. the holes were close to 1/4" off and the bolts were too short as the original flexplate was beveled is as the new one is flat. Any idea as too why? Would this also have different timing windows? I ask because, we wanted to hear this motor run before pulling trans back to replace the flexplate. It cranks and tries to start but acts like the timing is too advanced. I also was dealing with a code of no crank reference signal at the PCM. I have tested through all of the wiring to and sensor to eliminate bad wiring, bad sensor. All that leaves is bad PCM. I need to make clear that I had the crank signal pcm problem prior to new engine install.

96 and 97 flexplates are identical, part number 5211 8551.

Would a computer out of an 97 wj with 4.0 be the same as a 96 xj? I know where I could borrow a computer from a 97' grand with 4.0 to try my computer theory before bying one.

The cross-reference on a WJ computer says 96-98, and it looks identical. I don't think you can hurt anything by trying it. You sure the donor came out of an XJ and not a Grand? That might explain the flexplate being different.

I'm thinking you might have a bad CPS sensor.

CPS has been changed twice, as I have gotten bad "new" parts before.
Why is their a difference in xj and wj flex plate?
Could their be a difference in timing windows?
When I go to reinstall the original flexplate, do I need to TDC and measure for the correct window, or is their only one way to install?
Thanks so much for your help.

It only goes one way.

dakotaNCA said:

Why is their a difference in xj and wj flex plate? Could their be a difference in timing windows?

Click to expand...

The WJ uses a Chrysler tranny versus the AW4. I don't know if the timing windows are different, although I can't image why they would be. It might be the windows sit further aft or forward compared to the AW4 flexplate. Where they even the same diameter?

They were the same diameter, as the starter engauges fine. The only difference I saw ( unfortunately too late ) was the bevel in on the original and the bolt holes being a smaller diameter pattern. So the bolts were too short/ converter would not come closer/ if the holes had been oval shaped. So now I know. I plan to swipe..... uh I mean borrow the PCM from my buddys 97' grand and try it. Proving this motor to run will get my wife off my backside about this being a money pit. Thank you.