Spent 15 years in a rock quarry and a few of them as a mechanic. Got fairly familiar with diesel engines. Not bad yo work on just bigger. Rule of thumb was for a previously running machine 2 things would keep it from running. 1 is air and other is fuel. Kinds liked tearing one down and rebuilding it. Don't know if i could do that now. It's been 20+ years since i did that kind of work.