I'm trying to locate the power save relay as the battery is going flat after just a couple of days.Jaguar XK8.

SOURCE: battery goes flat after couple of days

sounds like there is something draining your bat, as, its dificult to say what as it could be anything, thats doing it, you need to get a multi meter leave the bat in, and check all elecy wires for any surge can take along time, to sus out the fault, when you check out the electrics make sure all is switched of switch them on and see if you are getting the say reading, not a job for someone thats not sure what to look for

SOURCE: Flat battery

suspect slack fan belt, therefore not charging battery.

Testimonial: "After further testing, it seems the clutch off of the alternator (I have active suspension) has gone, making the alternator over work which caused the wineing. Alternator now burnt out!!!! Both being replaced as I type, will update with an outcome ASAP."

SOURCE: 97 jaguar xjr supercharged had been in storage And tried to cold start. Nothing. Replaced fuel injectors, radiator, starting relay, fuel filter and battery. Still nothing. Would timing chain be the m

There are many possible causes why it won't start, but when it was not used for a long time I would check the fuel line. Only one bubble of air can stop the free flow of fuel.
Or a dried out dirty filter in the line.
Try to suck the fuel up to the fuel pump and check if the pump really delivers fuel.