03 mustang will not turn over

Check to see if you have fuel pressure. Inspect the fuel pump and fuel pressure regulator.

What I would do first of all, is to check and see if you're getting spark or gas..... Try having someone to attempt to start up your vehicle with to see if you're getting fire, if not , check to see if you're getting gas.... If you're getting both and your vehicle still won't start...... Check your tinning chain!