Thanks for your suggestion that it is the starter. Unfortunately it cranks fine for as long as i would ask. The battery is new 1 year old. The problem of not starting when left hot for 5 mins or so is someting else to do with the engine/egr/vacuum/fuel or something . The problem i first noticed on a hot day lust summer O3 when it failed to start after going into bank during lunchtime. I called AAA for a tow. When the truck arrived after say 50 mins the driver tried to start it and it did not for him also. So it is not user trouble! Put it on flatbed drove 10mins to their garage and their mechanic tried before unloading from flatbed and it started first time! They said unless fault was present it would be difficult to find. I drove all last winter 10,000 miles no problem. This summer it has happen twice both times going to the post office. Again leaving a hot truck for 5 mins or so then trying to start it. What i have fond so far to cure this is to wait one hour for the engine to cool or the vaccuum fuel or something to go back to cold start condtitions and it always starts first time and runs perfeclty. The second time it happened a work collegue suggested to remove the fuel filler cap to release any pressure. I did this and it did not start. Only thing so far is to wait 1hour.

What other engine components do think could do this?