I posted here by mistake. This is posted on the "Modern" forum as well. If mod remove this it's ok.

As the title states, when the engine (4.2) is fully warmed after a drive and I make a short stop, for an errand in a store or such. The engine will crank , but not start. In all occasions if I wait for about 10-15 minutes the car starts and runs fine. This does not happen all the time. I may go a week or more and then suddenly there is that time where it will not start and I have to just sit and wait.

I have replaced the thermostat. It was broken. It didn't correct the problem. It posts no codes. I thought I was replacing the fuel filter , but the part ended up being the fuel flange. I replaced it anyway, no difference.

Has anyone had this problem and actually found an answer.

Additionally where is the fuel filter located in a 2010 XF. Is it part of the fuel pump assembly? Or is it located somewhere else?

 

And when it is not up to temperature can You start it after shutting off with no problems? If yes then I would suspect maybe a vapor lock in the fuel line. I don't know about 4.2 in x250, but AJ126 in x260 has a fuel system without return line. If it is alike then maybe the purge valve is not working

Second idea is the crankshaft position sensor, but then the lack of correct signal from it would be stored in the ecu..