What is this plug?
 

Ignore the red arrow please, the yellow arrow and circled plug there. I just bought a 98 XJ with the 4.0L IL6 and I found this unplugged? What is it?

http://i802.photobucket.com/albums/y.../EngineBay.jpg

Oil pressure sending unit I believe.

x2, it's what makes the oil pressure gauge work

So would that mean that if it isn't plugged I just wont get a reading on the Oil Pressure gauge? Or would it cause worse problems!? Sorry for the stupid questions but the Jeep just stopped running and I'm trying to get to the problem. Haha

No. I don't think it would cause your jeep to quit running. It just sends the info to your gauge.

You said it quit running? What happens when you try to start it?

Check for fuel at the rail, unscrew the cap and press in on the valve with a screwdriver...use a rag to catch the fuel. Could be fuel pump, fuel filter.

Could be lots of things I am currently working on my fuel pump issue.

Well it would run for like 10 minutes and then I'd here a clicking sound with the press of the gas pedal and also at idle. While I was heading back I had to stop at a stop sign and she died at the stop! :( I took the battery out because it was nastily corroded and I am going to replace that. Also the thermostat was not in the housing when I bought it and when the car died there was a lot of smoke/steam coming from what looked like the radiator! So I have the radiator about out (damn lower hose wont disconnect) and I plan to replace that too! I don't know why it quit but I really want to get it going so I can start having some fun! Thanks a lot guys!