Beta 20hp BD722 - crank case fumes

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Ammonite

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I've recently discovered that the rocker cover on my BD722 was leaking crank case fumes past one of the cover securing screws - one of the nut / washers securing the cover wasn't seated properly and when I pulled over the rocker cover / crankcase breather off the inlet manifold and blew down it it was obvious where the problem was. Job sorted or so I throught. As a check I put my thumb over the dip stick tube and blew down the breather pipe again and could clearly hear air escaping from below the fuel pump. I've changed the O ring where the dip stick tube enters the block but the leak (assuming the crankcase should be air tight?) is coming from a recess in the base of the fuel pump. I can't really get at it to see what's happening properly. Anyone know if it should do this or what the problem might be? The seal between the block and the pump itself seems fine. I'm going to call Beta tomorrow but wondered if anyone here knows what's going on. The engine itself runs fine, starts immediately, doesn't use any oil (no leaks) or water and has done around 700 hours. It's just been filling the cabin with fumes, although I think most were coming from the rocker cover. Thanks in advance
 
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I don't think it's rings as there is no abnormal build up of pressure, no smoke or oil leaks etc. If you disconnect the crank case breather from the inlet manifold you'll end up with a boat full of fumes even with a new engine when the oil gets hot which is effectively what I had by not securing one of the rocker cover nuts properly. That's why a lot of engines are designed to consume their own crankcase fumes by routing the breather to the inlet manifold or air filter housing. My point it that I thought (rightly or wrongly) that the crankcase should be airtight when you pull off the breather and blow down it with you thumb over the dipstick tube. Mine isn't - OK it's only a small leak but it's definitely a leak which seems to be coming from the base of the mechanical fuel pump.
 
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crank case fumes

I have a Beta 20 BD722, which has done over 800 hours. Runs perfectly, and is serviced regularly, but it does produce fumes. I doubt if these are in any way exhaust fumes, as I have held a co2/carbon monoxide sensor in the engine compartment and it doesn't go off. Usually at the end of a passage when the engine has been running, I open the engine hatch to clear the fumes. Not sure what causes them, also don't think (yet) that there are any adverse health effects.

One thing I have noticed is that the air intake puffs air out as well as sucking it in. Wondered if this has anything to do with it. Engine seems ok otherwise. But have today emailed Beta Marine to see what they say.
 
Thanks, yes had a look at the diesel leak thread. The fumes I get are not from diesel, but I'll check pipe. The fumes are also quite well contained within within the engine compartment. Will explore the air intake valve suggestion.
 
Fumes from Engine

Could the problem be that the air intake system also acts as the breather system as well? The breather seems to be connected to the intake manifold. I have heard several comments about how rapidly the air intake filter becomes black. If breather fumes are being sent through it, that might account for it. I attach an image relating to this suggestion. Does it seem a plausible reason for the fumes in my case?
 
Have spoken to Beta Marine. They say rocker breather valve should take many thousands of hours use and some oil fume smell is inevitable from a hot diesel engine. However they suggest possibility of a sticking valve and I might want to follow that through by taking rocker cover off and lightly tapping valve rods with a plastic hammer. Another cause they say might be over-filling with oil, but this is not the case on my engine.
 
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