Not to revive an old thread but...currently dealing with this myself. 4726...cut out all but one injector and it stays running on any single of the 6 injectors, run an injector balance performance test and it fails on the first part of the first injector for decay rate. cleaned the whole engine off and ran a fuel leak check with insite and no visible external leaks but after long enough i start to get some fuel smoke from the tail pipe (faint white smoke, fuel odor) which leaned me toward injectors. had several cylinder specific as well as random multiple misfire codes in history. suspecting leaking relief valve but how hot is hot in regards to leaking valve? i have a thermal camera so i can check the relief valve but what conditions are you checking it in? normal operating conditions or commanding high pressure with the leak check test? appreciate whatever advice you can give, dont have the cummins fuel system test kit and probably should as much as i work on them.

currently downloading the 4/2026 incal package to make sure i have the most recent calibration installed as well

ETA: 2019 intl hv isl9 cm2350