Kohler Generator making unusual noise

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garmstro55

garmstro55

Senior Member
Joined
Mar 25, 2018
Messages
405
Location
USA
Vessel Name
Seventh Sojourn
Vessel Make
Mainship 400
Generator is a Kohler 8kw diesel generator, 2004 vintage.

Saturday, after running for about 3-4 hours it started making a clanking/rattling noise. I shut it down in less than 15 seconds after the noise started.

On Sunday, I started the genny and there was no noise and it ran normally. I did not have time to try running it under load, however.

I plan on running under load the next time I am at the boat, but what are the possible problems to look for?
 
Loose connection of the generator to the engine, loose alternator, seawater pump, coolant circulation pump trouble, loose belt drive pulleys, failing bearings.
Lots of other sources .

If no luck then get a mechanics stethoscope, auto parts supply, and use it to help zero into the source or at the least the general area. Just be very careful when examining anything running.
 
Went back yesterday with a stethoscope and, of course, it doesn't make the noise anymore. Ran for about 45 minutes under load. Now I am baffled.
 
I was once haunted by a ghost noise from a generator. It would come and go. Nearly drove me mad trying to identify the source. It turned out to be something loose that would at times rattle against the generator. Not part of or connected to the generator.
 
Hey Gary, do you still have your sound shield installed? Maybe it is rattling?
 
Dougcole said:
Hey Gary, do you still have your sound shield installed? Maybe it is rattling?
Click to expand...
A Forum Friend, I think his name was Dave or Doug, yeah Doug, once said to remove the sound shield and throw it away. I followed Dave's - I mean Doug's - advice so no sound shield. It did occur to me that something was rattling. I figure the engine wouldn't run normally if there was something wrong with it. Its not likely to fix itself. I will just have to run it and see if it happens again!
 
garmstro55 said:
A Forum Friend, I think his name was Dave or Doug, yeah Doug, once said to remove the sound shield and throw it away. I followed Dave's - I mean Doug's - advice so no sound shield. It did occur to me that something was rattling. I figure the engine wouldn't run normally if there was something wrong with it. Its not likely to fix itself. I will just have to run it and see if it happens again!
Click to expand...
Nobody likes a smart Alec, Gary. Lol.

Did you leave the frame in place, the part that holds the control board? Maybe it is rattling?

Just a thought.
 
I will take a good look at it next time at the boat. I hope that’s the problem.
 
A plugged or misfiring injector can sound like a rod knock in some engines. Especially 4 cylinder or less.
Sometimes the needle that opens the injector can stick causing the injector to misfire or fire late.
 
Lepke said:
A plugged or misfiring injector can sound like a rod knock in some engines. Especially 4 cylinder or less.
Sometimes the needle that opens the injector can stick causing the injector to misfire or fire late.
Click to expand...
Interesting. It did sound like something internal knocking, but I turned it off so quickly that I didn't really have a chance to open the lazarette and get a better look (listen?) at it. It ran just fine with no noise a few days later.

Question: Is it possible that the needle freed itself? Also, if it recurs, what is the cure? Is there something I can add to the fuel to help?
 
Every time I have seen this problem, it fixed itself. But if the injectors haven't been rebuilt since 2004 I'd think about it.
The sticking needle is most common in engines that sit for long periods.
 
That's good advice for a winter project. I would like to purchase one injector to have as a spare and online prices seem to range from $400 to over $600! Does that seem reasonable? Does anyone have a connection where I might be able to find a rebuilt injector?
 
About 4 yrs ago I had a similar problem.Same genset as yours in my 1999 MS 350. I had overnighted at a dock without power and the Genny had been running continuously for 12hrs straight. I was drinking my morning coffee when the diesel purr turned to a god awful noise that sounded like a thrown connecting rod or a broken rocker arm... definitely sounded internal . The genset had about 1800 hours on it! I shut it down restarted and it was still there. I travel 2 hrs back to my slip...restarted...noise still there. I was depressed to say the least. I go home and start researching replacement generators. The Marina owner who has been a yacht mechanic for 45 yrs started it next day. Noise still there. Said he was going to have to unbolt genset and slide forward to large lazarette opening to even pull the valve cover! I'm even more depressed. Well, the next day ,just for the hell of it, I started the damn thing. NO NOISE! I restarted again. Still sounded normal. I have put about 600 hrs on it since without hearing the sound of destruction...or so I thought. Go figure. The clogged injector theory advanced here sounds logical and was also mentioned by my mechanic friend. I hope you have figured out the problem.
 
The noise never came back. We went on a 561 mile 54 hour voyage and ran it the whole time and it ran flawlessly. Changed both fuel filters just to be safe.
 
Does anyone have a connection where I might be able to find a rebuilt injector?

Kohler may have an industrial or farm use of the same engine. I'd look there for injectors or ebay.

You should be able to have all your injectors rebuilt for $500. Probably less.
 
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