Hard Start ML 350 2007
 

my truck has a hard start...crankshat sensor was changed ..didn't help...merc ran codes but nothing comes up ...grrr... cold start is no problem .... but it's a hard/no start when car is hot and driven... have then to wait for an hour or two to restart... please advise

I would suggest to try one more crank sensor before spending any money on other components. Is the engine cranking fine but not firing? Or starter not turning at all when hot? If it is cranking but not starting, have them exchange the sensor for new one. Make sure to clean the sensor hole in bell housing from any dirt to minimize heat transfer from engine to sensor (that is why sensor body has a 3 ribs, if you look closer).
Also make sure to get the oem Bosch, mine is in for about 3 years without any trouble.
Bernard