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3406E · 06-16-2026, **(Subject: 12.7 60 series DDEC3 hard start )**

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 · 06-18-2026, **(Subject: 12.7 60 series DDEC3 hard start )**

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

Kw9006nz · 06-18-2026, **(Subject: 12.7 60 series DDEC3 hard start )**

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

3406E · 08-06-2026, **(Subject: 12.7 60 series DDEC3 hard start )**

He had the injectors changed just now, went for a spin ,truck started to vibrate and shut off on the side of the interstate. 6 new reman injectors from freightliner. Also said he was hearing a knocking sound. He’s waiting on a tow currently.

Rawze · 08-07-2026, **(Subject: 12.7 60 series DDEC3 hard start )**

(08-06-2026 )3406E Wrote: He had the injectors changed just now, went for a spin ,truck started to vibrate and shut off on the side of the interstate. 6 new reman injectors from freightliner. Also said he was hearing a knocking sound. He’s waiting on a tow currently.

maybe its time for a newer model truck/engine instead of trying to run freight with an antique roads show that belongs in an RV or a museum there?.

3406E · 08-07-2026, **(Subject: 12.7 60 series DDEC3 hard start )**

lol. It was one of the injector bolt that broke, they must have over torqued it. I think it’s a 2018 truck but he put back older motor in it 2020 I think out of a dump truck that rolled over. He never had any issues till now. He brags about his fuel mileage daily lol.