Yeah but the fuel pump and injectors are electric. So not much longer than a gas engine. Like I said, it will still leave you stranded just like every other vehicle on the road today.

 

The fuel pump will draw some, but it is low pressure. It's also possible that the engine would run without the small lift pump, especially if the pump quit when the engine was already running. Duramax diesels did not use a lift pump at all for a long time, not sure if they do on the new L5P engine.

The injectors on the 6.7L are piezo-stack. The stack moves a tiny valve which uses pre-primed hydraulic pressure in the injector to open a larger assembly which allows the main fuel charge in (up to 7 times per cylinder per firing). The piezo stack uses less electricity than a standard gasoline port fuel injector.

And if you had two large, fully-charged batteries when the alternator quit...yep...I'd still place my bets on the 6.7L staying running a lot longer than an equivalent 6.2L gas V8 truck.

But you are right, eventually the batteries will die and the truck will strand you. I just think the diesel could stay running longer.

 

Yes the motor will run for a long time ...but the transmission will start to shut down. Had it happen where it wouldnt shift down and was starting off in 4th gear from a stop and drive to reverse was acting up as well as getting it into park