I have a 97 cummins and you'll be driving down the road fine then it'll start cutting out and blowing white smoke but after about 30 Seconds it clears. It does this frequently while driving. What could this be?

 

Check for leaks, it's some how cutting fuel pressure wheather you overflow valve is failing, lift pump is failing, leaking in air, loose line somewhere. Check all that. If you have money and time/mechanical skill Id just upgrade the fuel system to a fass and put in a tork tek ofv. While you do that you can check the whole system. And basically the only thing not new is the engine side. Fuel systems are riddled with possibilities to failure due to age. Just my 2 cents. If you find nothing wrong with your supply to the pump and no leaks you may be looking at bad injectors or pump.

 

Most likely is air bubbles being suctioned into the system thru old oxidized cracked rubber fuel lines. A loose-fitting fuel-filter gasket won't do you any favors, either. White smoke and reduced power is pretty much an air-bubble trademark. The question is: "Where from?"

 

There is a rubber O ring going into the fuel screen/heater. With age that little bugger will crack and let air into the system. Cheap but not so easy to replace.