I've got a 1996 XJ sport, 4.0, 4wd, 5 speed, with 220K mi. Tried to start the jeep yesterday after it sat for about 7 days. It started to turn over then everything went dead, no power on anything. Turned key off and about 1 min later, everything came back on. Check batt voltage and 12.6VDC on batt. Cleaned up both pos and neg terminals on batt and tried again. This time, the starter never even turned over, just everything went dead (lost all power). Turned off and about 1 min later, power came back on. Tried same thing this time while monitoring bat voltage with multimeter and voltage on bat barely even moved (maybe a 0.05 VDC drop). I've got aftermarket bat connectors so removed wires and cleaned them up. Same thing. Pulled the starter relay and tried to start and as expected, nothing happened. Power stayed on but of course the starter never tried to engage. Reinstalled starter relay and tried to start. Power shutoff again. After poking around the engine for several min looking for possible wiring issues, I tried again and engine fired right up.
My question is this, I've had some strange electrical issues lately with the door locks and windows where they work sometimes and don't work others. Could these issues be related? Would a bad ground on the ECM cause this? I suspect I have a bad ground somewhere. This weekend, I'm going to clean up the ground wiring connection going to the engine block possibly the positive connection to the starter. Any other suggestions? Thanks.

 

Yes, all of this could be due to bad or corroded connections, especially ground connections. You were right to go after the battery posts first, but you'll need to give everything a once over. Given your description of the problem, this may be all that is needed. (Let's cross our fingers that there is no physical wiring issues, but that its limited to connections).

Btw, I troubleshot the -exact- same symptoms on my Jeep just a few months ago. And cleaning up the ground connections was all it took to rectify it. (primarily the ground connection from the battery negative to the chassis, and the battery negative post/clamp were my culprits).

 

Thanks, and that was a great video. I didn't know about the firewall or the dip stick ground.