Jeep Cherokee 96 Straight 6 4.0L

so i did a parasitic test and found that with the power off and keys out my mini fuse (20) was drawing amps from the battery. so i pulled it out and fixed the power draw however i dont know where to begin looking for wires touching or wires grounding out. that fuse seemed to power the whole interior so..also i replaced my spark plugs and pulled one, it was black. I also pulled my front o2 sensor and it was black (also new). so i guess the question would be where do i start looking for wires touching on the interior or grounding themselves out and what are the MAIN things that cause a jeep to run rich. thanks guys