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Old 26-09-2016, 13:27   #1
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Yanmar 3GM30F just shut off while idling

Yesterday, I was motoring for about 50 minutes out of the Oakland estuary at max RPM for my engine, trying to find wind on a hot, windless day. I hoisted the sails and was idling/cooling down when the engine just shut off. I was able to restart it again right after, but it sounded sluggish, so I shut it down the right way and didn't start it up again for another hour or so. It wasn't fuel or an air bubble, engine temperatures seemed normal, water was flowing well and the exhaust elbow had recently been replaced. Later, I noticed that it seemed to be idling a little low (900 RPMs) and skipping a beat so I kept it at 1000 RPMs. Two questions...does a shutdown like this cause any problems and might this mean that the injectors need to be cleaned? I suppose there are all sorts of possibilities here, but my main concern actually is whether it might have done any damage. The manual says not shutting down properly can cause bad juju
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Old 26-09-2016, 13:39   #2
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Re: Yanmar 3GM30F just shut off while idling

I have two Yanmar 3GM30F in my catamaran, and I have about 4500 hours on each engine. I am still using the original injectors, and the motors have always worked great. I have no idea why the engine shut off, but i would suspect a fuel problem. There were no signs of overheating.

If there is water in the fuel, that could easily shut an engine down. I don't think it would harm the engine itself, but water would hurt the high pressure injection pump because it depends on diesel fuel for lubrication.
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Old 26-09-2016, 17:14   #3
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Re: Yanmar 3GM30F just shut off while idling

Hi Gamayun, no need to worry I doubt you have done any damage, very unlikely. 99% of problems with these engines are fuel related. Look for a little vacuum leak in fuel line connections etc. I just replaced crush washers on secondary filter connections which were causing a little vacuum leak.

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Old 26-09-2016, 18:05   #4
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Re: Yanmar 3GM30F just shut off while idling

I filled the tank up just before this weekend so I would:n't think it would be water. It does seem plausible for it to be related to the fuel. I'll look at it carefully and see if I can feel a leak somewhere. I've read how hard it is to isolate something lIke that. Nevertheless, good to know it probably didn't cause any problems for the engine.
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Old 27-09-2016, 08:12   #5
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Re: Yanmar 3GM30F just shut off while idling

Almost certainly fuel problem somewhere. The fact that you just filled up may be significant. Or not! Stirred up sediment in tank? Batch of bad fuel? Water in the fuel? Changed your filters lately? A fuel leak may not be enough to starve the engine unless it's a big one. But the tiniest little air leak can do it. I think that is unlikely though unless you just worked on it recently. I'd change the filters and see what happens. Just be absolutely scrupulous with your seals, cleanliness and connections so you don't inadvertently create a second problem or you'll really be chasing your tail.
As for bad juju, you'll need a shaman for that.
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Old 27-09-2016, 08:16   #6
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Re: Yanmar 3GM30F just shut off while idling

We had the same thing happen this year on our brand new 1968 Dufour Arpege. Mechanic couldn't figure it out after I drained and polished the fuel tank, replaced hoses, new clamps everywhere, stripped bleeder screws from opening/closing too many times, etc.. Was told to see if the prop was fouled, it was not. Finally went to put more diesel in the tank while sputtering on a test run, spilled some as is my way, and discovered that my bright yellow cans had been filled by the finest dockhand in North Carolina with high grade gasoline. NOT DIESEL!!! Short story...replaced fuel, ran Sea Foam through her, and she's again purring. Just a bizarre unlikely thing to check since I don't think anyone would have except by accident.
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Old 27-09-2016, 08:19   #7
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Re: Yanmar 3GM30F just shut off while idling

I'm going to vote for a clogged filter (probably) or water in the gas ( could be but mostly filter). That would cause the symptoms.
You can also check the tightness of the banjo bolts at the fuel pump and filter as they sometimes vibrate a tad loose.

The engine shutting down by it's self would not harm the engine. Hydro-locking would harm it.
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Old 27-09-2016, 08:28   #8
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Re: Yanmar 3GM30F just shut off while idling

I have to he same engine, I suspect that it's fuel related. Make sure that you not only inspect/replace the Racor, but also the secondary filter mounted on the engine. I would start there. I was informed by a Yanmar mech that the secondary is frequently overlooked and needs to be changed as much as the primary. I have a shop manual for that engine in PDF if you need a copy.
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