why wont my 1996 xj6 jaquar wont start

Well you got different body control modules one in the trunk which controls your outer light and then you have one on the inside passenger side under glove box. Humidity from the a/c or some type of moisture compromised the body control module if you look thru Craig list or ebay; now they go for about 100 to 400 bucks if you got a "pick in pull" type of spot they go for 50 bucks or less. the way you test this is to check your relays under the seat and get you a volt meter and see the switch on and off voltage. If voltage is present with the switch off there's your problem. they are for sale ever where so look around also write your vin number and contact your nearest deal to insure you get the right model coded BCM

Part 2: It could be a vacuum leak at the intake or hoes on the intake get someone to smoke the motor and check for vacuum leaks around the mass airflow meter; if that didnt do the trick the worst of all throttle body (Attached the idle control motor is stuck) now most purist say replace it I say get some gum out or B13 carb cleaner and a tooth brush and scrub the throttle body (make sure you rinse all the gunk out it will get into the throttle bodies bearing(s) butter fly valve stems and thats a whole other problem... (if you remove the Ide air motor you gonna need a tap and screw remover the little bolts break off easy. Now if it doesnt start after all that then listen for the fuel pump wine; check your fuel pump fuses and check your fuel pump relay or have someone turn the switch and check the valve on the fuel rail to see if any fuel sprays out (watch your eyes) if it dribbles then a forty buck pump and a lotta work in the trunk you got to replace the pump. (go to partsgeek.com for cheap original jag parts)