I recently came into a 1989 Comanche 4.0L 5 speed manual 4x4 (Pioneer trim). It's rusty, lifted at least 6 inches on 31s, and doesn't run. I could get it to crank over with a battery jump starter, but of course with the dead battery, that cranks slow; however, it wasn't getting fuel. I replaced the fuel pump and tried cranking it over, but again, really slow, and low enough voltage I felt like the starter was using all the power (therefore fuel pump couldn't pump). So I decided to grab my 2000 Cherokee and use jumper cables, but after hooking it up, the Comanche still showed low voltage on the dash, and cranked over even slower than before. I used my multimeter and checked to make sure the cables were actually transferring power from the XJ to the MJ (under the hood of the XJ is extremely muddy), and everything checked out. I still cleaned the connections anyways, but nothing helped. It was basically just clicking like it had a dead battery. So next I took the battery out of my XJ and put it into the MJ and it just clicked like the battery was dead. Multimeter showed 12.7V at the battery, but the MJ dash showed 9V. I tried cleaning connections again, but still just a click like dead battery. When I put the battery back in the XJ, it fired right up like normal, no slow cranking, so I know it wasn't the battery. So now I'm at a loss.
A couple things maybe worth noting:
1) When cranking slowly with the battery jump starter, the battery cables would get really hot, like it had to draw a lot of current to slowly crank.
2) A lot of the dash is taken apart as the previous owner said he planned on chopping the whole front off and replacing everything from the doors forward with a 99 XJ (which I will not be doing). The cluster is still plugged in and seems to be working correctly.
Any direction would be appreciated. My first thought is that maybe the starter motor is bad, so it's taking a lot of power but cranking slowly. But before I start throwing money at a project I'm just gonna beat up off road (it's way too rusty to restore and only cost me $250), I'd like to see if anyone here has had the same issue.
I know that the 97+ exhaust is different from the pre-97s. I am currently 99 swapping my Comanche and that's one of the first things I noticed when dropping the cross member for the trans. I am not sure of the compatibility between Comanche and Cherokee, though. I'd imagine for similar year models (and engine sizes) it's the same up to the cross member, then different from there back for the truck vs the SUV. Someone else will have to chime in to confirm or correct this. That said, I don't think it would be as far off as your picture shows it being, you might have a damaged exhaust, possibly a few inches below the flange where the down pipe connects to the header.