First things first. Does the clicking sound that you are hearing come from the fuse box or from the motor (ie, starter)? If not sure, is the clicking coming from near the brake booster in the back corner of the engine bay or is it coming from under the engine somewhere? If the noise is coming from under the engine, then most likely it is a bad starter. If it is coming from the corner of the engine bay, may be a bad starter or interconnecting wiring.

Find the alternator (generator) and find the plug associated with the alternator. Find the black wire coming off of the plug. Connect a multimeter between the black wire (red lead on the multimeter) and chassis ground (black lead of multimeter). When attempting to start the car, what does the multimeter read? If under 11.0 VDC, then you have a bad battery cable, replace the cable between the battery and the starter. If the voltage stays constant with no change, then your problem lies with either a bad relay, bad wiring, or a bad solenoid on the starter itself. See below for further troubleshooting guidance. If the voltage remains above 11.0 VDC but falls slightly, then that confirms a bad starter.

If you think that you have a bad starter relay, interconnecting wiring, or a bad solenoid on the starter, you will need to move the red lead on the multimeter to the white/red wire on the starter (small terminal on the starter). Attempt to start the motor again. Does the multimeter jump to over 11.0 VDC? If yes, bad starter, replace starter. If no, then remove the starter relay (forward most relay against the fender on the passenger side of the car near the back corner). Now, install a short piece of wire between pins 3 and 5 of the relay box where the relay used to be. Does the motor turn over now? if yes, you have a bad relay. If no, then you have a problem with the wire between the relay box and the starter.

Hope this helps. If you need me to explain anything more, let me know.

 

Check your mega fuse in the trunk to left of the fusebox they come loose and create voltage drops. Check connections under hood passenger side under boot . This melt causing voltage drops. Also on early xks the trigger wire is to tight sometimes they fall off. On the starter

 

the same thing happened to me. it turned out to be the battery mine was dead after a week of cold snap. try pulling the battery and taking it to have it tested, (if you can hook up a trickle charger to the cables so you don't have to reset your codes). as to the jump starting issue, jaguars are almost imposible to jump start. good luck.