i have a 90 cummins when i bought it, it seemed to run fine. a few months later it started making kind of a miss fire sound, it progressively got worse to where no it has absolutely no power and at idle it blows white smoke when pressing on the pedal there is nothing but black smoke and back fires, it starts right up everytime though. i have no clue where to start any help would be greatly appreciated thanks!

 

check your oil.does it look normal or have a white or brownish slime on dipstick?

 

Non intercooled engines are bad for cracking heads between the valves n injector bores. Do you have any coolant loss at all? Also when's the last time you changed the fuel filter? Might even the injection pump itself but I'm leaning more to a cracked head or head gasket.

 

the oil looks normal and i changed the fuel filter when it started acting up as well as the oil and oil filter nothing out of the normal in the oil

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also there is no coolant loss
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Okay uhm fire it up crack one injector line at a time. It should be spraying fuel a few feet in the air when you crack the lines also make sure your heads away from the engine when you do it. You don't fuel under pressure spraying in your eyes. Tell me what it's doing if there's lots of bubbles little fuel coming out or what. Though I'm leaning towards a injection pump that's gone south. How many miles are on it?

 

i will do that later on today thank you, and 110 k orginial miles