12.7 60 series DDEC3 hard start

[3406E]

Asking for friend. Motor takes very long to start and idle horrible after firing up. It eventually start to idle fine afterwards. Check valve was changed at the back of the motor and problem went away for about two weeks he said but Back to square one now. It runs fine while driving no issues no blue smoke. The blow by is moderate for a 12.7.Also if he drives it and Shut it off it will fire back right back up easy, but hard start if left overnight. Fuel pump changed too.Engine has around 700k, to add he for reference he idles it a lot in the summer times for ac overnight. The motor has never been rebuilt before it came out of dump truck western start wreck. Appreciate your suggestions.