Any Detroit diesel guys here?

You did not say what model DDA engine? 8V92TA maybe?
Most likely you have a fueling/air issue.
Air filter restriction?
Leaky injectors
How many service hours on the engine?
Perhaps low on compression, have you every had a tech run the fuel rack, compression test, fuel pressures ?

I know next to nothing about the engine. I did state above that I did not know the model, but could find out this week.

That being said, there is no hour meter to be found, nothing has been tested. This company does not like to spend money on mechanics (our crane has been barely hanging on for a full year now).

Basically I'm at the "I've tried nothing and I'm all out of ideas" stage of this issue. Just trying to get an idea of what easy stuff to start, while I gather more information in the meantime. I hate to say it, but if it's more involved than a filter change and basic maintenance, the issue will likely remain unresolved due to management's unwillingness to spend money.