So here's my problem. I have done the big 3 on other cars and I can't figure out why it won't work on my 2007 jaguar x type 3.0 auto.
I wired everything like this in the picture. When I did it the car was completely dead other than the oil light was on in the gauge cluster with no key in the ignition. It would not start.
I switched everything back to stock and it works fine.
I don't understand my problem. The only electrical path change I made was I went from the alternator straight to the battery and then from the battery to the starter. I bought terminals with 3 terminals for wires.
I had also added a ground from the head to the frame where the battery ground is.

 

I'm mostly guessing, but I would say maybe the alternator needs to be directly wired to the starter for some reason.

 

bigbigbrig, from the sounds of things, it is sounding like you don't have a power problem, but a ground problem. Your problem lies with the ground wire going to the battery negative terminal. The ground wire coming from the battery should run 2 places. 1 is to the motor, the other to the body of the car. If you remove the ground going to the body of the car, a lot of the stuff inside the cab of the car and back will not work as it has no return path. Wire up the car like you had, but add a wire from the negative post to the body of the car and see what you have then.

As for why the car is wired with the alternator output to the starter is more one of convenience while the car is being built. By running the power wire along the firewall vice by the radiator or across the top of the motor, it stays out of the way as they are mating the motor to the body of the car. Electrically, it is all the same.

 

Thanks for the replies. I'm going to redo it this coming weekend with both grounds installed. I'll let you know how it goes.