Those speakers the PO left you are pretty nice!! 225W components are powerful speakers!! But, I agree with ktwalker01 in that there more than likely was an amp powering those speakers... 225W speakers need help, the CD deck you have may be lucky to crank out 50W to them speakers... Without the assisted amplifier, your sound will be very high pitched. So, if you want to keep those speakers, your going to need an amp. Other wise, send them my way, and I'll hook ya up with some OEM speakers :laugh3:
Its really tough to say what you are dealing with, cause it sure seems like the PO just kinda ripped out what he wanted at the last minute, and kinda let it up to you to clean up. I would say pick up a cheap multi-meter, something with OHM measurement. That feature will be the most convenient in tracking down bad connections or wires. Make sure you know how to use it properly. Do some research... learn a bit about car wiring. Its all DC, so its usually rather simple!
Its very odd to me why your PO left that combination of lose wires... A shot in the dark could be that the PO ran his own, new (probably heavier guage) speaker wire. The black clip is the OEM harness that would plug right to the original speaker. Test that. Unless you are getting OEM speakers put back in, id cut that connector off, and hook up a speaker, and see if there is sound. Look for a black connector like that on the other rear speaker. It should be there somewhere??
I read a previous post on this thread suggested removing the PO's wires. That is a wise place to start. First off, look around the jeep, see if you can find some sort of amplifier. (im assuming there is none, as you probably would have mentioned that?) Assuming no amp anymore, Verify these wires are connected at the back of your stereo:
NOTE! you may not have all the wires, just track down the ones for your speakers. Make sure the speaker ones are connecting to the back of your radio.
This should verify that sound is now pumping through your OEM speaker wires. Then, attach the speakers to the OEM wires. If no sound, either wires are interrupted, or the CD deck has blown outputs. To check for blown outputs, eliminate the broken wire variable. Hook up a speaker directly to the back of the stereo using your own wire.
If an amp was installed, the OEM speaker wire could have been compromised at any place. Being that your one driver door speaker is working, I would see how that one is hooked up. If its hooked up through OEM colored wires, there may be hope!
Its all trial and error. Hope you can figure it out. Sorry for such a long post... just throwing out anything that might help. Good luck!