2001 dodge ram 2500 cumins diesel motor is running rough and has white smoke coming from the exhaust What can the problem be Drained water from the fuel and it ran good for a little while?

White smoke is either from too low of an operating temperature or air in the fule system. Check to see if water temp is in normal range, change thermostat if not. If that isn't the problem Pop the hood and see if there is any fuel leaking any where; filter, injection pump, fuel lines or injectors. I had a loose injection line that caused the same problem, tightening it back doun fixed the problem.

Drain the filter again and catch what you drain. If there is water in there, you need to drain and clean your fuel tank.

also one other thing is white smoke can mean head gaskets are bad when you start it go to your exhust and smell for a sweet smell if so you do smell that then water is going into heads from radiatior or i know this for gas motor but diesel should be the same