wont start

I just bought a 2001 gmc sierra with the 6.6 duramax. it ran fine for the first few hours i had it. i went to take a drive after it sat for about 20 minutes and it started then died as i went down my drive way and would not start back. after buying a new glow plug control unit it would not start...

I have an 03 lb7 truck has been in the shop for 2 months new injection pump installed worked fine for a week back to the shop on trailer. Now after spending all that money it will not fire back up. Got it started finally now truck smokes excessively at take off and when driving. It never did...