When I turn the key, all power goes off. I changed starter, starter relay switch, starter relay. Still will not crank. Just shuts all power off until I release key, then power turns on. What am I not doing or what should I replace next? Also tried starting in neutral, and it does the same thing. Just turns power off.

 

Sounds like the security lock out BS I was dealing with some time back.. Look up "security relearn process" for your specific year and try that. Nothing fixed my issue, it just stopped being an issue one day.

 

There is probably an old post on here that covers that exact same issue. I can't recall where it is for sure. However without knowing more about the car. My first thoughts are to the Ground connections. The second thing I think of is the Battery if it has any age on it at all it could be the problem. When it is cranking the car it needs to be 12.8 to 14.6 Volts if I remember correctly. If you only got 11 volts it won't start.
I have also provided a link for further research with he same subject.

https://www.google.com/search?client...+won%27t+start