i just bought my first diesel pickup, its a 1994 reg. cab cummins with a 5spd, and just recently it has started to knock funny, my dads 3rd gen just went through 6 injectors and sounded a little similar to what mine is doing, if i park and rev the motor while its warming up it blows alot of blue smoke.... if its just injectors i can deal with those,

oh ya its got 244k on it

 

12 valve injectors don't fail as often and early as the common rail ones.
Your blue smoke sounds more like a cold engine.
Does it still do it after it's warmed up?

If it's knocking at idle you can isolate it by loosening the injector lines a part turn at each injector one at a time. Loosening the bad one won't change the engine sound, the other ones will.
Beware of getting fuel injected though your skin.

With that many miles I'd pull the injectors and have them tested/rebuilt or just buy new ones.
When removing injectors don't bend the lines, remove the entire line from both ends.

 

thanks that helps alot! it does do it when its warmed up, at higher rpms it feels like there is a miss

 

Try to find some bio-diesel , get an extra fuel filter or two , keep them on the truck , mix about 25% bio with 75% #2 , it may not want to start in 3-7 days , filter plugged , change filter .
Bio-diesel , is at this time the best cleaner & lube out there for diesels .
Also , check the fuel pressure , should be about 22-26 psi at idle , 28-36 psi at 2,000 RPM no load .
Using infidel's suggestion on finding the offending injector-s .
The way I look at is , do maintainance 1st , then the easiest testing 2nd , the harder testing 3rd [ in this case , removing & pop testing , while looking at spray pattern ] , never replace parts with out at least 1 if not 2 tests telling that the part is bad .

 

i got oil a fuel filters for it yesterday but didnt have enough time to change them, i will do that as soon as i can, i am looking to upgrade the injectors eventually so if it is an injector it may just speed up the process,