We have a 2007 Dodge Ram 1500 Flex Fuel. It ran completely out of gas. Put $20 back in and it still won't crank. Checked a couple spark plugs, replaced battery and terminals. Plugs are getting a spark. When we crank the truck the engine turns over but will not start. Fuel pump does come on and gas comes out of the schrader (sp) valve. Not sure where to go from here. Any help on what to try next would be great. Thanks in advance!