What is wrong with my van?

My Van which is a Doge Caravan 3.8 1986 was cutting off at stop signs and lights. I recently got the fuel tank strap that was rusted off replaced and the check engine light was on and it was diagnosed as an oxygen sensor. Then they reset it and it was still cutting off and the light never came back on. The van would start up when it wanted to and run for 2 days without cutting of then it did it again and again. Now it won't start at all. It acts like it wants to start when you turn the ignition key but it won't turn over. Do you have any ideals?