ShaunTX

I'm troubleshooting my son's 91 Cherokee (Manual trans) and am really scratching my head at this point. So far the battery and starter have been replaced with no difference in symptoms. He has an LED light bar and stereo with amp/sub, but all have been disconnected while we try to chase this problem down. I've begun monitoring voltage and voltage from the battery to the starter is reading around 12.8v with the key off. What is odd is that as soon as I turn the key to the ACC or ON position my voltage drops down to around 3 volts and slowly starts creeping back up, but doesn't get much higher than around 5.5V.
Question 1:
Is that much of a voltage drop normal when turning the key to the ON/ACC position?

I put this on Jumper Cables thinking the voltage wasn't enough to power the starter, but the symptoms were no different. At this point I'm about to pull all the fuses from the internal fuse box and monitor voltage drop while I insert them one at a time. I'm fairly certain I've got a short somewhere but my mechanic-fu is limited.
Question 2:
Is there a better, more sensible way to try to figure this out?

Other notes:
-All battery terminals have been cleaned.
-Screwdriver-jumping at the starter causes a click, but doesn't turn the engine over.
-Manual push and clutch-pop start works fine.

Any assistance is greatly appreciated.

Cheddarnut

Throw the battery on a tester, might have a bad cell. Might be worth upgrading the main grounds and cables and going with a higher amp alternator with all that stuff. If you think about it the original system didn't have the big light bar, amp etc. So the battery might not be getting recovered enough by the factory alternator(also worth testing as well).

ShaunTX

So my initial reply was "The cables haven't changed...it can't be the cables". I decided to cut the ends off of the positive cable since it looked a little corroded. What I noticed was the small red wire (that I now know to be the starter relay wire) was hanging on by two small strands of the ~14 AWG wire. I pulled the terminal connector apart and used my Dremel to wire brush it perfectly clean, stripped the terminal wire to get fresh copper, stripped the starter relay wire to get good copper and reconnected everything. Damn thing started right up after that.

So the moral of the story is to start with the wires...clean them...then move on to the other things....appreciate the help Cheddarnut.

Cheddarnut

Always glad for relatively easy fixes. Great work tracking it down!