When to change?

HelpinUout go to Rawze.com and ask him about this issue and how to fix it. Again i had this issue on series 60 and fixed it by replacing only O-rings.

 

You stated it was his injector CUP. I did not know it was an ISX. Which motor? The CM-870, 871, 2250 or 2350? Two different animals in that bunch, especially when it comes to the heads and injectors. If that is soot, he has very serious issues. I would not drive the truck until it is fixed.

 

it's 2014 and must be 2350. i guess one of bottom o-rings is bad. if you remove the injector you better replace all O-rings near injector.

 

Ok, and good advice sending him over to Rawze. CM-871 here, Rawze saved my bacon a couple of years ago... MM.

I wonder if the poster knows about the fuel pump?

 

Halp, you really need to get that looked at if you do not know what the real problem is. If you want real sound advice, go over to Rawze.com, it is a 100% Cummins ISX site. Open an account there, it is free, and there are real mechanics there, along with many owner operators that have been through similar issues.

Do you have any diagnostic equipment, like an Inline 5 or 6 reader with Cummins Insite? There are some other tests you can run, there are videos there that walk you through them in regards to testing injectors. You really need to diagnose this issue, as the motor you have can turn on you very very quickly, and it will not be pretty.

Do you know about the fuel pump issues that your particular motor may have? If it is a CM-2250 or CM-2350 you have a ticking time bomb on your hands. I see you have the 2350.

Get over there to Rawze.com, explain your problem, tell them which motor you have, and make and model of truck, post all of that information and one of the guys, or Rawze himself will get back to you. I don't mean to scare you, but these motors are nothing to play with.