PLEASE HELP '96 jeep cherokee won't start

so i dont know much about cars, but my dad knows enough to get around, so any help will be appreciated. my dad just had a seal of some sort between the transmission and the drive train replaced b/c it was leaking trans fluid, and drove it home, it ran fine, he parked it, and i came home and tried to start it, and it wouldnt start, nothing happened, it wouldnt even attempt to do anything, i thought it was the battery, so i asked dad to help me jump it, and after about 10 tries or so, dad started giving it gas to get it to start, and it finally did, but you had to keep the rpm's up over 1500 or it would just die...except for the leaking trans fluid, i've never had any problem with it...what could it be?? its a '96 jeep cherokee sport 2WD with a 4.0 liter 6 cylinder engine...thanks for the help!! you can message here, or email be at bigredhokiefan@gmail.com

--Alex

Sounds like it might be a problem with one of the vacuum lines, most notably the one going to the MAP sensor. Check them first and make sure they're all connected and the lines don't have any holes or cracks or anything in them.

There is a very touchy sensor called the CPS (crankshaft position sensor) that's located at the 11-o'clock position on the bellhousing of the transmission. (drivers side)

The CPS is the mother-of-all pain in the ass sensors. It's really hard to get at, and will cause your rig to do all kinds of eratic starting behaviors. ie- hard start and/or no start issues like you're descibing.

A new CPS is around $100 on its own. Here's a link for more detail...
http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm
Scroll down 2/3 or so... This is what I'm putting my $ on.

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics/Crankshaft_Position_Sensor.jpg

http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics/Crankshaft_Position_Sensor_diagram.jpg
~Good Luck!