You have a 1991 ford e150 van with a 350 and when you first start it up starts fine the 2nd time you start it up befor an hour goes by it wont start you have replaced the battrey and spark pluson it s?

I had the same problem on my 1988 and would have to leave it on. On that motor, there is a heat shield that surrounds the starter and if it is not there, when the motor heats up it will transfer that heat to the starter simulating a bad battery/starter problem. Once it cools down it starts fine. Start looking from there or get a remote starter (like I did) so you can leave it running when you run into somewhere fast. I had the same problem on my 1988 and would have to leave it on. On that motor, there is a heat shield that surrounds the starter and if it is not there, when the motor heats up it will transfer that heat to the starter simulating a bad battery/starter problem. Once it cools down it starts fine. Start looking from there or get a remote starter (like I did) so you can leave it running when you run into somewhere fast.