I'm a retired GM Tech (48 years). I have CDJR vehicles because of the minimal amount of repairs I have needed to do on them compared to anything GM or ford I've had. I recently got a 2020 2500 6.4L with a "bad engine" at an auction (146k miles, $12,400). After changing the 15w40 Rotella (fleet vehicle moron mechanic) out with 0w40 Valvoline Synthetic and 3 filter changes it now has proper oil pressure. It has a misfire code for #3 (why always #3?) (I have a new set of coils for it) and something I haven't heard since carbs and distributors, spark knock. It's not lifter tick, I know what that sound is I had it on my '11 RAM 1500 5.7L (another retired fleet vehicle). I put a cam and set of lifters in that one at 139K and it now has 368k. Anyone know what I might be dealing with on the spark knock? It also has the long crank issue. I put my bypass harness in the TIPM and it still happens, so maybe not the fuel pump relay in the TIPM? What is normal fuel pressure supposed to be? Any tips are welcome.

 

Thanks for not helping. I'm outta here. Bye.

 

Sorry you feel that way, but I do not own that type of truck and I do not know about the 6.4L at all. It's not that no one wants to help you, but we cannot think of where to go from here. If you have misfire code on #3, then I would start checking valves and other mechanical things since the electrical side has been replaced. Unless you have a bad troubleshooting card in the computer, what else could it be? I don't know.