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Old 01-07-2013, 15:31   #1
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Yanmar 3gm30 dies after running

My 3gm30f Yanmar has now died a few times after running hard for several hours - perhaps 8 hours. I have two engines and the other is doing fine. She just shuts down. I wait a while and she starts right back up; however, she will shut down again, but sooner than the original time - perhaps only after 2 hours.

I have recently replaced my fuel filters and coolant. I also have replaced the impeller pump and water flows freely through the cooling system.

Any thoughts on what might be wrong?

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Old 01-07-2013, 15:56   #2
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Re: Yanmar 3gm30 dies after running

Assuming the fuel tank breather is venting OK, it can either be fuel restriction or air, check your air intake hose isn't collapsing/delaminating under vacuum when hot, that leaves fuel, it can either be floating debris in the tank blocking the intake(this took me days to workout on our site JCB) or sediment in the tank blocking the intake. Remedy, clean the fuel tanks ! There are more problems on this site than any other with fuel and the majority are caused by failing to bite the bullet and clean the fuel tanks. Our family business is collection/delivery/storage/polishing/filtration of bulk liquids and diesel fuels left in storage will sediment fine sand dust/Gummy deposits/Wet fuel. These deposits form a very fine shiny black liver like substance, modern additives like rapeseed oil act as a cleaner and these deposits come adrift as glutinous flakes and can easily block intake lines which is why we do not proscribe to the very expensive Raccor fuel polishing systems suggested for boats. We have to clean our storage tanks of this crud after each use despite polishing whilst in storage.

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Old 01-07-2013, 15:59   #3
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We used to have issues with the pickups on the fuel tanks clogging up when running under load... I would check the pick up...
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Old 01-07-2013, 16:06   #4
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Re: Yanmar 3gm30 dies after running

This is most likely to be air ingress to the system. Fuel restrictions due to sludge or solid debris is more likely to stay in the lines once it has got in there.
Therefore I would look at all the fastenings, hose condition (especially where hoses pass through bulkheads) O-rings and gaskets of the supply filters of the fuel supply system from the tank to the injection pump. All of which is under a depression when the engine runs so can suck in air.

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Old 01-07-2013, 16:07   #5
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Re: Yanmar 3gm30 dies after running

I assume this is when you are at sea ?...Sounds like crud pick up...or air...

Do both engines take their feed from the same tank ??
See you out there ....... Alan S.V. Elyse
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Old 01-07-2013, 19:02   #6
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Re: Yanmar 3gm30 dies after running

Originally Posted by Irish rambler View Post
Assuming the fuel tank breather is venting OK,
I would say that is the most likely cause, particularly if the symptoms are consistent. In that case, I would expect it to happen sooner on a full tank due to faster vacuum buildup.

If you get any indication it is about to die, a simple test would be to remove the fuel filler cap and see if that keeps it running. It's also possible that as the tank vacuum increases, your fuel supply hose gets restricted and closes off the flow. Once the restriction starts it could close off quite suddenly.

Your dilemma is the hours of motoring before it goes bad. So I would be checking out the other ideas suggested here.
Currently cruising Queensland coast
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Old 01-07-2013, 19:34   #7
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The key statement is that you recently replaced your fuel filters.

I would replace the ones going to the failing diesel again. Do you have one primary and two secondary engine mounted filters? The seal may not be perfect and air could be getting in. Replace and bleed the system. I'm not sure that sludge would be getting through new filters or that the motor would run for 8 hours if that was the problem.

Also check every bleed fitting to make sure they are air tight.

Most problems like this appear after you change filters.

ΩOne question: Was the motor running perfectly before you changed the filter?
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Old 02-07-2013, 06:49   #8
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Re: Yanmar 3gm30 dies after running

Many thanks to all who have responded. Your thoughts and suggestions make sense. Indeed, this engine feeds off one tank and the other engine a separate one. This problem did occur one time on the same engine, the port one, before I changed the filters. The port tank does appear to have a venting issue. I'll do as advised and check all the connections and vent. Thanks again.

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