look guys im a big jeep fan i have a j-10, willys, and a cj 5 me and my brothers have a jeep family i never had a jeep give me problems like my cherokee tho i love it and i just put a rebuilt engine in it it ran great for about a month and a half it ran wonderful i was just on my way to clombiana 4wd to pick up a 4 in lift for it when i tryed to start it it would turn over but not even attampt to start! i called all my jeep guys up for some help because i couldn't figure this out we found that its not getting spark when u first turn it over it will then drops back down to 0 when we checked it with a meter i was told to take it into a shop and ask a pro but im a fix it myself kinda girl and i only make 250 a month so i dont gotta lot of money to work with here i replaced spark plugs roter and cap someone told me that it could be the coil thats what i thought i replaced it still no start its not the ignition switch because it also got replaced its not the starter its getting fuel so its nothing to do with that(you dont wanna know how i found that out lol)and no the battery is not dead lol i wish someone could help me with this i know that :

-getting spark then droping to 0 has to mean something big i just dont know what my poor lil jeep is saying

seggestions would be greatly appreciated  

What do you mean the spark is dropping to zero?
Are you losing it after you crank it over for a bit?
How long does it take to do this?  

Check the crank position sensor located at the back of the block on top of the bellhousing. I believe it is located on the drivers side. There should be a test to check it out with a multi meter but im not near a manual to tell you what it is. This is what I found on autozone.com http://www.autozone.com/az/cds/en_us/0900823d/80/04/f5/7e/0900823d8004f57e/repairInfoPages.htm  

err date, some shoot me  

I had my cherokee do the same thing awhile back it turned out to be the cam sensor/pick up sensor. It is located in the distributor, my local parts store had the sensor for $35 or the entire distributor for $125. It's not hard to change the sensor that's what I did. Another problem could be the muffler or cat is clogged, another problem I had, my flowmaster muffler delta flow plates broke loose and clogged it, the jeep wouldn't start no matter what, I pulled off the exhaust to change out O2 sensor( it was the only one I didn't change, I then tried to start it( open headers! I'm a redneck) and it started, changed the muffler and no problems since. hope this helps out some.