All my lights are coming on, my radio everything. But whenever I try to start it everything just turns off. Every once in awhile if i keep trying eventually it will start. Any ideas????

 

First start by checking the large fuses in the PDU under the hood. Make sure none of them are blown. From there if they look alright, pull the starter relay out of the PDU (the PDU cover will tell you what one). With a multimeter check pin 86 to your fender ground (look on the side of the relay for the pin numbers), it should read 0.0v with the key off, have someone turn the key to the START position then take notice what voltage your meter reads, you should get +12v. If you don't, then something is probably wrong with your NSS (neutral safety switch), your key cylinder or your ignition switch. Try that and report back!

 

My first drive after I paid for my XJ I couldn't get anything to work while it was running. no radio no heat nothing. But it was running. So I called the guy back and was like WTF is going on you sold me a pile. Turns out my ignition is a little sticky and sometimes you have to help it back into the correct position. Whew!

 

To be more clear:
When you turn key to "start" things shut off, and there is no cranking?
Could be ignition switch (key) or relay unit.
But don't quote me on it.

 

When i put the key in the on position everything turns on lights, and electronics wise. But when i try to start everything goes off besides my lights in my gauge cluster

 

I did everything you said. I couldn't find my multimeter pin so I gotta go pick one up

 

I would suggest grabbing one, they range any were from 10 bucks to 100's. Testing that relay pin in the PDU to the ground will show you if the relay is getting the 12v it needs. If it isn't then your issue is a sensor or switch, if you do get the 12v then your issue is a blown fuse or a dieing starter solenoid/starter motor.