2 things can cause white smoke. Burning antifreeze or a lean condition.
Check your antifreeze and engine oil, if they are OK and you have'nt had any overheating problems then it's probably fuel related.
Those mechanical fuel injectors dont fail often but it's possible.
Most likely cause is the mechanical lift pump mounted to the engine block on the drivers side rear. There is also a fuel heater next to the lift pump that has a screen in it which plugs up over time and is often overlooked. And it goes without saying, check the fuel filter.
If you still havent foud the problem have a cummins technician check your high pressure injection pump and injectors.
Best of Luck!
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