1989 Jaguar XJS car will not start

THE BATTERY IS BRAND NEW AND IT HAD A FULL CHARGE COULD IT BE THE SWITCH ON THE SHIFT LEVER?

I do not have a voltmeter but it is a new battery and I put it on a battery charger and gave it a slow charge and it was fully charged when it would not turn over I switched batterys from my 1985 coupe and car would not turn over both batterys start the 85 xjs I also tried battery from my explorer I do not think the battery is the problem is there a fuse for starter

Hi, I own what must be the all time lemon of the 1989 Jaguar XJS'. Your going to love this. I had intermittent & pretty much unexplainable probs with the battery/alt/starter circuit for years. Had me pulling my hair out.I mean really relays, diodes, more relays. On & on. SO THIS IS THE SCOOP - if the battery, alternator & starter are fine go to the starter relay, its silver, rectangular with 2 wing attachment for screws on the passenger side of the engine compartment toward the firewall. OK now, there are like 6 prongs or more, pull off the black wire with a green stripe and attach a spare wire to that prong/blade and then ground that wire to something metal. Try to start the car. Did it work? If it did, its the feed back relay (black square with an internal diode just to the right of the starter relay)Ok, now here;s the fix, keep the ground wire that you supplemented and replace the errant relay at your leisure. As long as its ground your cool. Do you believe they charge so much for something so simple? Egad, I hate most mechanics