Hey guys, this is my first time posting so I apologize in advance haha.

I've got an 2003 dually I bought for a work truck and run fine for a while.

I replaced the radiator and since for some reason everything went downhill in a hurry.

Truck had what I think was a knock from the CP3 but I'm not sure.

It progressively got harder to start, now barely starts at all. When it does bust off it runs for a few seconds and does. I've replaced the lift pump, added one to the tank, replaced the filter, and the FCA.

Also bought two new batteries. Checked fuses couldn't find anything and I'm at a dead end.

I think it's the CP3 but just trying to figure it out before I go to replace it.

Any suggestions would be great!

Thanks in advance.