Yanmar L48N diesel single cylinder running waterpump black exhaust smoke

   / Yanmar L48N diesel single cylinder running waterpump black exhaust smoke #1  

FordnMassey

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Jan 22, 2022
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ford 3000 and MF35
Hi,

I have an L48N single cyl air cooled diesel engine running a water pump that has become very smokey. The smoke is black and sooty, making soot on anything nearby. It was mild when I bought it second hand (unknown hours) around 100 hours ago, and suddenly became very heavy recently. It produces it at idle, light load and heavy load. I am trying to find the cause of the smoking. It sounds like it is producing less power and not quite reaching full rpm - I can't put a tachometer on it.

I pulled the injector and hand cranked the motor and produced 4 neat jets of diesel spray at 90deg to each other with no dribble before or after. I think this is fine. Following that I ran injector cleaner thru it and no change.

I pulled the oil fill cap while running and eased it clear for around 1 second. Large amounts of blow by are present - enough to think I was looking at an exhaust outlet.

I am figuring the smoke is sump oil being burnt, likely thru the rings, which are also the source of the blow by.

Questions:

1). Am I right in thinking rings?

2). can anyone suggest a tool set or brand/item number for compression testing this? Looking online at kits I see a variety of inserts but none appear to match the injector on the Yanmar.

3). Could a valve issue cause sufficient oil burn to give this appearance?

Thanks in advance for your help.

FordnMassey
 
   / Yanmar L48N diesel single cylinder running waterpump black exhaust smoke #2  

bmaverick

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Yanmar YM2610, retired JD 850, retired DYT-4000
There is a purposed thread for your Yanmar engine located here. It's rather extensive. On several pages, one can even find the manuals posted.


Seafoam is a great product to clean up the inside of the single piston motor without tearing it apart piece-by-piece.
 
   / Yanmar L48N diesel single cylinder running waterpump black exhaust smoke #3  

Roadworthy

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If you've not done so, check the air filter and the air path from there to the manifold. Perhaps you'll get lucky and that's all it is. (Perhaps not.)
 
   / Yanmar L48N diesel single cylinder running waterpump black exhaust smoke
  • Thread Starter
#4  
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FordnMassey

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Jan 22, 2022
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ford 3000 and MF35
Hi,
I should have said, I changed out the air filter, and ran it briefly without one and there was no improvement. I haven't inspected the air intake pathway fully tho, so will do. Nothing lost by looking there.
It wouldn't explain the blow by tho, unless I'm missing something.
Thanks for your reply.
FordnMassey
 
   / Yanmar L48N diesel single cylinder running waterpump black exhaust smoke #5  

ponytug

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I think that if you are getting significant crankcase blow by, my bet would be on rings. You might take the valve cover off to check there, just in case a valve seal has gone.

All the best,

Peter
 
Last edited:
   / Yanmar L48N diesel single cylinder running waterpump black exhaust smoke
  • Thread Starter
#6  
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FordnMassey

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ford 3000 and MF35
Hi,
Thanks for the replies. I'll pull the head and the piston and see what I find.
Thanks
FordnMassey
 
 
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