Electrical problems, need ideas please
 

This is my first post here, I searched and read every forum post for ideas. I'm hoping out of the wealth of knowledge on this forum somone could give me some input, thanks..

I apologize for the long read, but I'm truly out of ideas and need help from another brain.

I tried jump starting my project car today with my 96 miata and when I touched the ground to the project car battery, if sparked quite big. Well me being the overly excited dumb*** I tend to be, decided it wasn't a big deal and continued to start the Miata up.

Then I moved the jumper cables for a better connection and the jumper cables arced terribly... I continued with my attempt to start the project car, and when I got the project car started, I disconnected the jumper cables and let the Miata idle. Then the Miata just died, barely cranked, and wouldn't start up... Okay, great... I threw the Miata battery on a charger and it wouldn't charge it. Then I see battery acid dripping down through the venting tubes... Okay, I figure I damaged the battery, I'll throw another one in and all will be well.

I put a spare battery in and I have no power to anything, check the 80amp main fuse and its blown. I buy a new one and throw it in, the second I hook up the battery again, the new fuse blows... I search for shorts in the wiring harness, but find none. I do some thinking and figure maybe the alternator got overloaded when the battery blew up and that's why the car shut off.

I pull it out, get it tested at a local auto parts store and it passes the test... Hmm... Okay, I buy another fuse while I'm there, go home and pop the new fuse in. I hook up the battery WITHOUT the alternator and it doesn't pop. I turn the key and my radiator fan comes on right away... That's weird...I try to start it and it only cranks, no start. I hook the alternator up reconnect the battery and the fuse blows.

I then jump the 80 amp fuse with the alternator disconnected and the alternator power wire is getting power. No shorts going to the alternator, but why would the fuse pop only when the alternator is connected? All the other fuses are fine. Why would it not be getting fuel or spark... I haven't tested for fuel or spark to see which one its not getting, is it possible I destroyed the fuel pump/ coil packs with that voltage spike? Did the ecu get fried?I'm truly out of ideas and need some input.

Thank you very much for any help you can provide

Is it possible you put the batter connections backwards?

I wish it were that simple but no, they are most definitely correct. They were also correct when I was jumping the project car.

Well there goes the most common cause for blowing the 80 amp fuse.