"Capt John" wrote in message
...

Well Bruce, if I was starving the engine to the point that the
injectors were no longer getting enough fuel to return any fuel via
the return line then, you surely realize that their would be a very
significant reduction in power output, to the point that the engine
would stall. In your case, your talking about a generator, if you put
an ammeter on the output of that generator you'll probably find that
it's not really loaded up to full capacity, they rarely are, except
when your starting electric motors. In our case, we're talking about
boats, that's the reason for this being under rec.boats, and boat
engines tend to be much more heavily loaded up than say a truck or a
generator engine, that's why they rate generators with a constant load
and intermittant load rating. In boats, what tends to happen is that
the filters start to clog up while your running, over time. Some of
the first signs of this are increased black smoke behind the boat (you
see a haze, it's not like a building on fire), soot buildup on the
transom around the exhaust, increased engine temperature and increased
exhaust temperature. At some point, if allowed to go on, the engine
begins to loose RPM's. Remenber, when you increase the throttle
setting on a diesel your increasing the amount of fuel delivered to
each cylinder and advancing the point where the fuel is injected. So
when the fuel system is restricted the amount of fuel delivered per
stroke drops slightly, but the advance doesn't change. Another symptom
of a restricted fuel supply is if you've been up and running, and you
have to slow down, for whatever reason, and then you try to come back
up to speed, the engines will not come back up to the same RPM's as
they were before.

All you have to do if for any reason you have to run at low load for a long
time then open up to as near as full power as you can get from time to time.
This will clear everything out from the nozzles and ensure that the exhaust
remains clear. It may not be easy always on a generator because you may not
be able to control the load but for a boat propulsion engine if you open her
up the prop will take the power as the power taken is proportional to revs
cubed. A diesel will not gum up its injectors unless you run it for long
periods at less than 1/2 or (better) 2/3 load without bursts of higher
power.