I purchased a 1984 XJS. The battery went dead, so

has your car got a aftermarket security system ? sounds like the ignition and/or the fuel pump is being isolated by a security system fault

Key fob battery dead?

Take the connectors off clean them with a terminal cleaner or a Brillo pad put back on tighten see if that works.

Hey!!!

I have a 1984 Ford Ranger and I understand your problem EXACTLY! I just got my truck fixed. I purchased a new voltage regulator (which is on the right of the truck under the hood on the inside fender portion) because my lights were going dim when I let off the gas. On that year of vehicle, the voltage regulator is prone to going out. I plugged my new one up thinking I had done some good but my battery kept going dead overnight. I finally went to the Ford dealership and they said my new one was drawing power away from the truck and killing my battery. They then tested the old one and said it was good.

Anyway, moral of the story is that your voltage regulator is probably bad. If you buy a new one, which is only $16, and it does the same thing.. take it back and get another one. Just cause it's new doesn't mean it's working properly!

Good Luck!

Also, feel free to ask me more questions about your 1983 Ford Ranger!

you need to check the injector and your fuel pump make sure you getting fuel

could just be a bad alternator it happens,i have gone thru 3 before it happens,go get another and try again.it is a mechanical part,and parts go bad ,does not matter you just bought it,it happens.good luck with your project.hope this helped.

I have the same car I had the same problem.If you have the correct battery for your car with the same problem you have a short or positive ground in your dash/electric fuel pump/fuse box also be carefull of how you take the key from the ignition and if they're old replace them.

Do you know the procedure for using a test light to pinpoint where draw in electrical system is?

have you had the alternator checked out?

Here is a link to the factory owners manual, the info about the fuse is in the manual.

http://www.motorcraftservice.com/pubs/content/~WO1TAU/~MUS~LEN/41/01tauog1e.pdf