I've never seen one die like that... with initially both cylinders running and then one cylinder running & other quitting & white smoke. My thoughts are perhaps it could be Injection pump timing, or... perhaps a bad injector on the failing cylinder. If a bad injector on one cylinder & its slowly dropping RPM's then the governor would request more fuel to maintain RPM thus over fueling the good cylinder until it quits? Just a thought...
Well...
I'm eating my own words now! Now I actually have seen one die like that as of today...one of my own units!!!
Got another weather alert today. We're expecting some more bad weather with the two "Bomb Cyclones" dancing together offshore in PNW with a high wind alert inland with expected power outages (over 500,000 are without power up in Washington State as of yesterday). So, I decided to fire up one of the house generators (Genset#2) for a readiness check. This was the same Genset, fairly pristine low hours unit, I used during the last outage during last winter's ice storm that took out power.
So I go out to start it & it seemed a little slow to start but since I hadn't started it for too long (last winter) it kind of stumbled a bit & then smoothed out. Then a few seconds later it starts to slow down losing RPM's & one cylinder drops out & engine then quits with white smoke! Holy cow this sounds familiar!!!
So, with all the fresh info from reading of "1Fast4's issues above" still in mind, I focused on listening to the fuel pumps. When I tried to restart it wouldn't restart. Hmmm, no clicking from fuel pumps. Got out my persuader screwdriver & tapped the plastic screwdriver end on the 2 inline fuel pumps. Suddenly I heard a faint slow click, kept tapping & then the click seemed a little louder and more frequent. Kept tapping on both & suddenly they both began a faster clicking cadence. So, then I attempted a restart & it came roaring back to life & I ran it for a good 15 minutes to get everything flowing & engine heated. Shut it down & came back out an hour later & it fired right up and ran well for another 15 minutes.
I treat all my fuel with BioBore & OptiLube XPD additives, however if fuel sits static in components for a few months & not flowing, apparently under the right conditions, it can gum up things like check valve balls, pistons in fuel pumps etc.
Anyway, lesson learned! "Exercise your gensets"
at least every 90 days or more frequently (monthly) if you can!