I recently have had this problem happen on my 2000 automatic V6 Explorer. It starts and runs perfect when there is no engine temp. But occasionally when the engine has temp it will not do anything on startup. It will not turn over, and i can't hear the starter or fuel pump doing anything. I've seen all the suggestions and I'm pretty sure it's not the vapor issue, the last time it happened I had just filled the tank and couldn't start leaving the gas station. Going to test some of the fuse/relay fixes tonight. I'm amazed at all the different possible fixes people have suggested.