When to change?

These parts need to be updated, just follow correct procedure from cummins quickserve.
Make sure use correct part numbers , because 2250 and 2350 plungers are different.

 

Thats isx high pressure fuel pump parts that fail. They have to be replaced every 400k miles. Upper pic: plungers and barrels assembly. Lower pic: tappet.
On 2250 plungers were ceramic and caused ceramic particles through the main bearings and oil cooler. In the middle of 2013 cummins put steel plungers. Older tappets had brass pin , now they put steel pins.

 

I did myself according to cummins quickserve manual. Plunger repair kit $120, tappets $300 , head gasket $20.
Once you unscrew old barrels they cannot be reused. New have steel washer that seals fuel. New barrels needs to be turned with torque wrench 60 ft lbs and then after that turn 60 degrees. Tappets needs to be alligned in pump assembly using guide pins in pump body, so they will be in correct position. If you do any mistakes doing this rebuild the pump can be damaged.
The fuel pump doesnt have to be removed from engine, you can remove pump's head while pump is on the block.

 

I had a problem last year of the filter blackening and took advice on using Biocide addictive. The problem isn't alge or fuel bacteria. It's soot. I used diesel fuel cleaning addictive used to clean fuel lines enjector and ur whole fuel system. I am problem free. Follow the instructions on the bottles as misuse could corrode.
Unless u are having problems with fuel supply to the motor or loss of power or fuel leak near around the fuel pump there is no reason for rebuilt this soon.
I have ISX and love it.

 

Remember You have a filter issue only