Dodge ram 5.7 hemi wont start.... fix!

This is my 2003 dodge ram 1500 with a 5.7 hemi engine. I just bought 3 days ago and didnt know anything about it. Until i notice it had no gas at all. Changing the spark plugs makes a big difference. Performance and better gas mileage. Before replacing them. I was getting 10mpg. Now im getting 14.7mpg. Much better. And more power.