Uneven idle (Yanmar YSM12)

[Ana]

Dear diesel whisperers!
My Yanmar YSM runs unevenly when on idle, not much but noticebly. I did not have this problem last season (I think).
Is it air in the system, dirty diesel or just the thing this motor does. These engines idle allways really rough, one horisontal piston.
I cleaned the tank last winter, it was full of stuff which should not have been there.

 

[vyv_cox]

It's a very long time since I had one of these engines but I do recall that salt accumulations in the cylinder head were a problem leading to uneven running. One long straight round passage was completely blocked and needed to be drilled out. Very easy to take the head off to check.

 

[rotrax]

I would check valve clearance first, if OK then take the injector out and have it tested.

I had a very high hour YSM 12 on a canal narrowboat.

I gave it a top end overhaul and had the injector done and it improved noticably. The fuel consumption dropped even more, and it was REALLY frugal to start with. The injector nozzle was weeping a little causing overfueling and rough running.

Not expensive to get a single injector tested.

Worth a punt.......................

 

[Norman_E]

Look at this video and compare your engine.

I think the video shows the engine ticking over too slowly, but no single cylinder is ever going to be completely smooth running.