Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust - SailNet Community
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post #1 of 15 Old 11-11-2014 Thread Starter
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Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

Hey everyone!

I've been trying to fix my motor problems with only using prior posts, but now I'm just stumped.

I had an overheat problem, so I took apart the whole cooling system, cleaned it all out and water cools perfectly.

Well after this the motor wouldn't start. So of course I go into troubleshoot mode. Fuel system cleaned out, both filters, etc. Turn out, the stop motor cable was pinched.

Now, I'm getting black smoke, soot, unburnt fuel (nuetral and in gear).
I took apart the intake manifold and breather, both seemed clear.
I took off the exhaust elbow again, clean.
I replaced all the feul injectors with brand new ones.
With the exhaust elbow off, I started the motor and there was still a ton of smoke.

What have I missed??

My concern is that the motor didnt smoke before I started repairing it, so I think I did something during repairs.

Thanks for any help!
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post #2 of 15 Old 11-11-2014 Thread Starter
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

Also, the black carbon coming out lays on the water like a dust, not like an oil spill.
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post #3 of 15 Old 11-11-2014
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

Wish I could help. Our Yanmar has always smoked black smoke at startup. Maybe yours is just catching up with the times.

See if the smoke goes away when the engine heats, see if you are burning oil - if all that checks just move on.

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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

Quote:
Originally Posted by Pamlicotraveler View Post
Wish I could help. Our Yanmar has always smoked black smoke at startup. Maybe yours is just catching up with the times.

See if the smoke goes away when the engine heats, see if you are burning oil - if all that checks just move on.
I wish it was just on startup. I took her out yesterday, and she smoked, carbon, the whole time I ran her.

Before I took her out yesterday, I ran the motor for about 30 mins at 2500-3000 rpm and it would clear up (no smoke, clear water).

I suppose I can have someone dive to check the prop.
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post #5 of 15 Old 11-11-2014
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

If it smokes in neutral it is not the prop. It is getting too much fuel.
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

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Originally Posted by jsaronson View Post
If it smokes in neutral it is not the prop. It is getting too much fuel.
That's what I was thinking...

So if the fuel injectors are brand new, how else would too much fuel be getting in?
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post #7 of 15 Old 11-11-2014
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

Black smoke is fuel not getting burnt properly (bad fuel/air ratio), not necessarily too much fuel, it could equally be not enough air getting in, a blockage in the exhaust system, or there is now too much load on the engine for some reason.
Is that all you changed, poked, prodded etc?

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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

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Black smoke is fuel not getting burnt properly (bad fuel/air ratio), not necessarily too much fuel, it could equally be not enough air getting in, a blockage in the exhaust system, or there is now too much load on the engine for some reason.
Is that all you changed, poked, prodded etc?
Yes, so far.

My air silencer is off (the clips broke). That's something that has changed.
Would too much air cause this?
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post #9 of 15 Old 11-11-2014
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

How about decompressor not fully disengaging? Do the injectors have the little heat insulating washers on the tips? Too many washers? Try a spray/pop test of injectors >Reinstall upside down and hanging. watch for even mist or dribble.
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post #10 of 15 Old 11-11-2014
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Re: Yanmar 3GMD unburnt fuel/ black smoke/ Exhaust

So no air filter? Have you sucked something up and partially blocking the intake?

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