Well after a little more time with the Xj the problem seems to persist. I have not cleaned and check the battery cables and replaced the electrical portion of the ignition switch. I am still having the same intermittent problem. Some times it starts right up and sometimes there is no power. Yesterday it failed again so I started trying to chase voltage from the battery. Everything in the engine bay seemed good. I grabbed the large plug that goes into the firewall on the driver side just below the booster. It seemed to be somewhat loose. I was able to tighten it up slightly and have not had the problem the last time I have driven it. I guess only time will tell....

Thanks again to all for the help.