Detroit Diesel 638 engine problem, please help

[MaxJacob]

Thanks for the tip, man! I'll be taking note of this.

[cowboywildbill]

Way back years ago I had a pin hole in a fuel line on a Brockway Cab Over Tractor. It didn't leak fuel out but would suck air in. Had the same symptoms as you are describing.
Was a pain to find. Finally just replaced all of the fuel line.
Let us know what you find.