I have a 1993 Jeep Grand Cherokee Laredo. It's been sitting in the yard for a few years, and this summer, I decided that I would try to get it running again. After doing a good deal of work on replacing the end-bearings, my oil-pan gasket, and my valve-cover gasket, I got it back together and ready to try, but it wouldn't start. I turned the key and just got one click. Not a series of clicks (as one does with a low battery) just one click, coming from the passenger side of the engine compartment. The battery is from another vehicle, but the other vehicle is running, and when switched back, the other vehicle had no problem starting. Removed and cleaned up the starter, took it into an auto-parts vendor, tested it, and it was fine. Ran a line straight from the battery to the positive lead on the starter, and was able to get it to turn over (coil was unplugged because I am just trying to get the oil pressure up at this point). Tested the line from the battery to the alternator, and it was fine. Suspect something between either the key and the starter, or battery and starter... Have no clue what I am doing when it comes to electronics... Any assistance would be much appreciated.