I have an 89 xj, cannot get engine to turn over. I have replaced the starter 3 times, it will work for about 2 days then cant get it started again after. You can hear the starter kicking out but wont crank the engine. I have checked the relay, starting it in neutral(didn't work), hitting starter with hammer, jumping the starter with a screwdriver and I cant think of anything else. Battery is good, all connections are good.

 

Maybe its not the starter? Check ur CPS?

 

No....CPS would let it crank. His don't crank.

You need to check 3 things.
Check for corrosion inside the pos wire between the battery and starter. Also check your engine grounds. If the grounds are crap it will fry your starter.

 

That.
Plenty of nice-looking cables with clean shiny connections that don't conduct worth a dime. They're corroded inside. Sometimes you can hear crunching when you bend them.
I bet if you measure the voltage drop between the battery terminal and the starter terminal while cranking, you'll find the problem.