I'm posting here to see if my "problem" should be of any concern.

When my runner has been sitting for a while (eg overnight and maybe even longer), I go out to turn it on and I get this knock or thud. I've had this happen about three times over the past month or so. The first two times was just one knock, the last one had two. It fires up just fine, the engine doesn't seem to be struggling, and after that initial start, all subsequent starts are just fine. Is this just a backfire or something from the setting fuel? Should I take it in to get it checked out? If I do, I'm going to have to leave it there for a while so they can recreate the the sound from it sitting for a while.

 

absolutley! Take it back!! If it wraps a little on start up now, what's it going to be like it say....75K. Take it back and get them to check it. Remember it's still free since it's in warranty. Take advantage of that warranty! Wish I still had a warranty

 

Sounds like you got the infamous piston slap knock of the I-Force V8 which has been well documented on tundrasolutions.com. Do a search for the topic "Diesel Knock Tracking". It's a pretty long thread of reading to do.

 

I called up the service manager, and he immediately said it was the fuel injector pulsating. The sound is only when it is cold, not while it is under load. So for now I am satisfied. If anything gets worse, I will take it in.