I just got my 91 to start after swapping a 88 motor in it. I put all the accessories off my 91. The two things that concern me are that the intake doesn't match the ports on the head and there is no place to bolt the coil to the block. My problem is that the motor won't restart after it gets hot. I'm wondering if it's a ground problem with the way I rigged up the coil to mount to the A/C bracket. If I pull the Fuel pump relay it will fire... Sometimes even run until it burns the off the gas. If it starts without the relay. I can reinstall the relay and it will start like normal. Any ideas about what's causing this? It does seem to have above average heat in the engine bay. Some have suggested a clogged cat. but it seems to have good power. Although, I've never driven a Cherokee before. Can a bad cat. cause it not to start when hot?

Back pressure will cause it to run hot and may stumble when hot but if it has been off for more than a few seconds it should not effect the ability to start. JMHO.

BTW My '90 has the coil mounted on the passenger side inner fenderwell.

I would start with grounds and remounting the coil.
Since these are items that will have to be addressed anyway.
Might as well get them out of the way.
And if by chance it cures the problem, you've just killed two birds with one stone.
But don't worry...I won't tell PETA