Engine turn over but doesnt keep running?

yesterday on our way home the 2004 ford freestar just didnt have any more power to go on. We turn the ignition on but it doesnt hold any power to keep going.

This may not be a solution, but I had a similar problem. I was driving at 70 mph on the freeway and the engine just stopped running. I pulled over and found that the service engine soon lite was on. I attempted to restart several times with no success. The tow truck driver went to the back and checked the emergency fuel shut off valve. He said it was tripped but would not reset. After towing it into the shop and have it trouble shot, the only things that was done to get it back on the road was clear the service engine light and reset the emergency shut off valve in the right rear (where the jack is) access panel. The codes were 171 and 174 which are very common. It seems that a hard bounce on the road can trip the valve and shut off fuel to the engine.