Hello,my motor has been rebuild because exhaust valve was melted and rod was bent,so they installed everything new .
When engine is cold it starts immidiatly and after driving I stop the engine and start immidiatly again there is also no problem,but when I shut down the engine and wait for about 30 minutes it's difficult to start,I always have to try 2 times before it starts.
There are no fault codes or cells,they also flashed the OEM program back but this doesn't help also .
Anybody got an idea what could cause this?
Thanks..

 

Fuel pump?

I would also do a leakdown test to verify the condition of your rebuild.

 

Thanks Kevin,how do you have to do a leakdown test ?