Its probably something simple. Check the solenoid on your starter. Sometimes tho things stick. Meter your battery make sure it has 12v with the truck off. And you can disconnect the line after the pump to ensure that the pump is working correctly. All that right there would take you about 10 minutes. If none of that fixes it then u probably have bigger issues. Or just it to another car really fast. See if it starts then. If so then your battery still could be shot. I know alot of time in summer if u drive around with ur a/c on alot and then park it and dont start it again for awhile then it kills ur battery. And yes 7-8v is enough to get it to make a crank noise but not enough to start it completely. Ive learned that the hard way. Hope that helps man.
2006 Dodge Ram 1500 QC 5.7L Hemi
2" Top Gun Customz Leveling kit