Diesel Won't Make Normal RPMs

[Yellowjacket]

Had a similar problem on 4JH-DTE. Had a v-belt fail with much dust, which clogged turbo, fouled the intercooler, etc. Could not get up to RPM, excessive black smoke, etc. Thorough cleaning did the trick.

[Elie]

Yes, but if this occur also when engine in neutral, it can't imply nothing but the engine itself. Air supply(black smoke = enough fuel) blocage in the exhaust subsystem, or dirty fuel, or fuel feed pump problem.

[Cadence]

Originally Posted by thunderhoof

The Perkins (Volvo Penta MD2030) on my sailboat suddenly refused to respond to the throttle to turn over 2100 rpm. The max rpm is listed as 3600 and I commonly use it at 2800 to 3200. The engine seems OK to that point with a steady idle at 800 rpm and smooth running up to 2100. When I try to advance the throttle past that the engine seems rough with some black smoke (not dense) from the exhaust. Behavior is the same in neutral and under way.
I have replaced the two fuel filters. There was no evidence of contamination or clogging and the drained fuel is clean with no water. I bled the fuel lines up to the injectors twice with no change in behavior. The three cylinders act the same while I am bleeding them. All drop about the same number of rpms and spray the same amount of fuel when I open the lines.
The engine is 2003 vintage with about 1200 hours on it.
Any ideas? My next step will be to remove the injectors and have them inspected / maintained / replaced.
After that I guess I have to have the injection pump tested. Is there any test I could perform on it while it is mounted to the engine?
Thanks in advance for any help you can supply.

Sounds as if you are sensible with your troubleshooting. But wait someone will say you missed the carbonator.

[thunderhoof]

You folks kept me on the right track by steering me away from the injectors / injection pump and toward air leak / fuel blockage.
The story: The boat was built 2003 and I acquired it in 2006. A few years later I installed a bulb priming pump in the line between the Racor and the low pressure pump on the engine. The other day when I changed the fuel filters I noticed that the short section of the line I had cut seemed cracked. So I replaced it with the fuel filters. The engine ran somewhat better but, at the time, I thought it was the filter change that helped. The longer section of hose seemed OK but When I flexed it hard it was clearly cracked near the Racor filter. I replaced that section today and the engine runs smoothly, in neutral, to 3200 rpm with no smoking.
The problem appears to have been an air leak when the suction in the fuel line reached a certain level.
I will replace the other section of hose, from tank to Racor, soon. It probably from the same lot as the hose that cracked after 14 years. Strange. The original hose is marked as an approved type and is not in a particularly hot or dirty area.
Thanks again for the inputs.

[Diesel Bill]

The best fix turns out to be the cheapest fix. I love it when things turn out like that.

[Wotname]

Thanks for the update; it's always good to hear the ending, especially when it is a happy ending.