1st Gen Cummins motor w/ 250k+ miles. Not 1st startup in the morning, but any time after that, I get a small puff of gray smoke out of the tailpipe. Is it unburnt fuel? More importantly, is it something I should be worrying about?

 

Sounds normal to me. Have you increased the idle or anything like that recently?
I wouldn't worry.

 

The VE pump on the 1st gens gives full fuel below idle speed, so you get a puff of smoke when they start. Mine belches out a big cloud of black smoke when started due to the injectors and turned up pump. This can be used for entertainment purposes.

 

Thanks for the reassurance. I'm like a new mom with this truck. I'll get used to it's foibles eventually.

 

That puff of smoke comes in handy sometimes. I had a guy cut me off and steal my parking space once. So I had to wait until another spot opened up and I parked on his passenger side. I didn't see him in the store but it turned out that I left the store right before he did. I sat in my seat with my fingers on the key and waited until he walked past my tailpipe and gave him a blast .hehe

 

Its even better when someoen is tailgating you and i just floor it then left off. all that smoke always gets them off your bumper