I am completely at a loss as to how to diagnose a problem on my brother's Cadillac and need help from those more familiar with it's specific electrical systems. I am about 90% certain it is a short but have no idea how to isolate the various branches so that i have any idea where to search for the short.
My brother was sitting in the car with the key in the accessory position to listen to the radio(after market stereo system) for about 20 minutes when he turned the key to start the engine all electrical went dead (i found this all out today). He calls me to get a jump thinking he drained the battery. When i arrived i hooked up the jumper cables to my kia, leaving it's engine running. I did get some sparks when i hooked up the negative side but that didn't register with me as a problem YET. After about 45-60 seconds the Cadillac's engine started to turn over with out any key in the ignition (or any-one in the car yet). Almost immediately my engine died and i rushed to remove the cables ( i was holding RPMs at about 2K) which were VERY hot. Too late, it had drained my battery to the point of not having enough to restart. After getting a jump from another car my Kia has been totally ok and seems to charge fine.
I had a friend use his flatbed to tow the Cadillac to my house...That car is so big it barely fits in my garage.
I pulled the battery and attempted to recharge it on 3 different chargers...it was COMPLETELY dead. I got a new battery for it and charged that to max. When installing it in the car i just hooked up the positive connection with 2 cables (i think Alt. and ignition feeds???) and the negative cable. All the interior systems and exterior lights, blinkers, etc. seem to be working and the dash read out a starter disabled warning (i think this is VATs???) after switching the key to on. The ignition switch detents feel correct and smooth.
Next i hooked up just the single cable connector (i believe the starter feed)and the instant i went to reconnect the negative cable sparks flew and the engine tried to turn over (again ignition in off with-out a key in it). The battery survived this momentary hook-up and after checking all the fuses in the engine compartment and trunk none of them blew. This leads me to believe that the starter solenoid has fused in the on position or there is a severe short in one of the branches of the starting circuit. Please tell me if that guess is wrong or right.
Now is there a way to test the starter for this with-out resorting to opening up the intake to get at it? What buffoon thought that the lifter valley was a good place to put a starter even if there are no lifters there? This same design was what i hated about the 89-95 ZR-1 Corvettes. Is there a way to isolate and separate the the starter relay and/or the ignition switch to test for the possibility that there is short away from the starter?
The only manuals he has to this Cadillac are a chilton's and a hayne's. Neither of those gives me a clear enough picture on how to deal with this problem...they seem to have tried to pack too many models and years into one book and left out WAY too many details that are needed for this kind of diagnostic. I am currently unemployed and my brother is in college so we don't have $120 to blow on the FSM if it doesn't have a reference to this problem or to waste on throwing parts at the problem till we get lucky and fix it. PLEASE, if you have any experience with this same problem let me know where to go from here. Or if you have the FSM for 94 Seville please look through it and let me know if it mentions this specific starting/charging problem.
Thank-you very much for any help you can give me on this.

 

So, today i spent a couple of hours playing with the Cadillac.
I removed the ignition switch and did my best to test for continuity through the different detents. There was no indication of a short, or any problem, with-in the switch. While the switch was out i hooked up the 2 wire positive connector to the battery while leaving the negative cable unattached. I then ran a voltage meter from the single wire positive connection and the battery negative lug. It read 13.6 volts...WT#???
Does any-one know where the starter relay is located on this model and year? If i pull that relay and still get the same results from voltage test does this indicate that the starter and/or it's cable are my only remaining possibilities for the short? The 2 books i have available to me show a relay before the starter but absolutely no indication where it is mounted on the car. If any-one knows where this relay is located PLEASE tell me. Thank-you.