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Old 28-09-2009, 12:52   #1
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Boat: jeannau sun fast 36
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Slight Knocking 3GM30F


I have slight knocking noise on my 3gm30 F.
It is less obvious in certain rpms.

What ca be the cause of this?
I have two theories.

1 a half bad injector
2 Could a worn con rod bearing cause this noise?

Or am I just paranoid.

is it normal with "diesel knocking sound"
I know that a diesel sounds different than a gasoline engine, but what is ok?

The noise is worse on start and cold engine.

Is there any sound recording of a good running gm somewhere?

Thanks. Hope you do not find my questions to weird.

Örjan Sterner
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Old 28-09-2009, 14:26   #2
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If you can get to the injector lines and are able to crack them loose at the injector while running, one at a time that is, you will able to determine which cylinder it might be in, also check to make sure its not a drive line knock, depending on the drive line you are using. Once you can determine the cylinder it's possible then there are further things one can do to find the problem. Be sure to keep an absorbent cloth around the injector line, where you are letting it loose.
The Artful Dodger
Passage 42 Centre Cockpit
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3gm, 3gm30

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