I'm helping my brother in law fix his 04 Cummins, truck is stock minus exhaust and intake, smarty (not installed). has 250k miles.

Issue is abnormal black smoke when accelerating and stutter, also idles rough and stutters when reving in park and will blow black smoke when reving in park as well. And a somewhat long crank imo. Maybe 3-4 seconds. No mil light

What I found when he dropped the truck off.
Gummed up fuel filter(very nasty almost sludge like)
Dirt in bottom on filter housing
Very dirty air cleaner
Fuel smelled weird and was red (i know farm) didn't smell right still

I replaced fuel filter flushed the lines. Drained and cleaned tank, cleaner airfilter.

The truck still has the symptoms. I put fresh fuel in and some diesel kleen. And drove it a little bit. Nothing changed.

What I know, truck has had Injectors replaced about 100k ish miles ago, and has the intank pump conversation. Truck ran fine last week and randomly did this.

I'm kinda stuck Im not sure how to guage fuel pressure and check rail pressure, or see Injector pulse/voltage. I have a small scanner that doenst pull up anything useful and I have a obdlink which doesn't show much either regarding Injection system. And my Alfa obd doesn't work on the truck.

Any and all help appreciated.

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