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.

[Rawze]

DO bull gear and thrust bearings... and inspect the rest. Replace old crank and other sensors.

[Kw9006nz]

I had this on an old 97 binder with the exact symptoms you discribe, it had a davco filter on it and after doing everything you say he's done I replaced with a new davco unit problem went away entirely

Maybe there is check valves in the davco that can be replaced but at the time I was young and just changed the unit as a whole