im putting my money on a worn injection pump after you test the glow plugs.

Sounds exactly like a school bus powered by a 6.5 I worked on a few years ago. Tough starts always, but once running, you could never say there was something wrong, just ran great after you finally managed to start it.

We tested all the glow plugs, replaced them all for good measure, tested all the injectors, and finally pulled and swapped the pump, which is really easy by the way on a 6.5.

That solved the problem, chances are your fuel lubricated injection pump has suffered a little from ULSD. When we pulled the old injection pump apart, it was full of galled surfaces and other worn areas.

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