This may not be an acurate test.. If there are any grounds that are not well secured the system will die whether the alt is good or not.. If you have a multimeter the best test you can get will be with this...

If you attempt the test again rather than disconnecting the neg you would disco the Pos.. if it continues to run then its not your alt..

 

I thought about that after i posted the last post. My buddy's got a meter and we're gonna try and test it tomorrow or maybe this weekend.

 

So my buddy and I tested the alternator with a meter and the battery's charged and the alternator is charging. Both were reading around 12 volts. but appareantly one of the power wires from the battery to the starter is losing about .5 volts, which i didn't know but could cause it to start hard. I sprayed some pb blaster on the starter connections and cleaned the battery terminals really well. Started it up, it still started slow but the battery guage was actually working for a minute or two. Then I went to drive it, and right after i got out of my apartment complex it starting trying to die on me. So i turned around and it was still sputtering (buddy's alternator crapped out on my friend's car one time and it felt like the same thing). BUT i hit the gas one good time and it was fine after that... I'm lost

 

a buddy of mine was mudding with us and he ruined his altenator packing it with mud, you could have the same problem
and no matter what if you take your negative battery cable off your vehicle will die
EDIT: Also 12 volts for altenator charging isnt good enough the altenator should be charging at around 14+ volts
just go buy a new altenator and your troubles will be solved il bet my left nut on it

 

i went mudding for the first time a long time ago and my starter went bad. could be your starter...

 

I was thinking it was supposed to charge around 14, not 12. But i kinda think it's both starter and alternator because now when i crank it there's a grinding sort of noise 2 or 3 seconds after it starts. And I just went to Wal Mart and it wouldn't crank back up because it was dead, got a jump and it barely ran back home because the battery died again.

 

ALSO me and my friend are going to a junkyard next week to try and find a starter and alternator.

Anyone know of a starter or alternator or both i could get from a different vehicle that will work? Just in case they don't have a xj.

Or do you know if an older model xj will work?