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jcullain 11-13-2012 08:29 AM

Kubota rattle
Hello Forum! Our first post here, and it is a tough problem!

We recently purchased a "rebuilt" Kubota EB300 diesel generator. It ran great for a while, but has been developing a "rattle".

When it happens, it quickly looses power, and rpm drops right down. It has been happening much more often lately. The noise sounds a lot like a hydraulic lifter rattle on a car, but of course this engine does not have those!

The boat is in Thailand, and the seller is in Australia ignoring my emails :(

Some things we checked:
Oil pressure great
Coolant temp normal
Load is within normal range
Very little or no smoke
Injector cleaned and reinstalled
fuel filter clean
The oil looked ok when changed, no metal particles

Any possible cause? We dread it may be something internal about to really go bad!


mm2187 11-13-2012 10:20 AM

Re: Kubota rattle
When is the last time you changed fuel filters? Does it sound like your engine is fuel istarved.

chucklesR 11-13-2012 10:34 AM

Re: Kubota rattle
OP says filter was / is clean; I'd look at the pump, and check the air filter and supply.

Depends on what is making the rattle, I doubt it's valves. Could be related to the 'starve' i.e., mounts, gen head, belts binding and or slapping.

Jerry, you've got to stick your head in there and really eyeball the whole thing and see if anything is moving that shouldn't, or shouldn't and is.
Is the rattle in sync with the rpm?

NCboatrx 11-13-2012 11:41 AM

Re: Kubota rattle
This could be caused by the injector. I suggest that you have it checked.

klem 11-13-2012 05:21 PM

Re: Kubota rattle
In addition to the above suggestions, here are 2 more. Try to pinpoint where on the engine the rattle is. If you have a stethoscope, this will work well, if not, hold a screwdriver with one end touching a part of the engine and the other your ear.

Also, if you can get a fuel pressure reading at the injection pump, that would help a lot.

jcullain 11-14-2012 01:20 AM

Re: Kubota rattle
Thanks for the advise!

As klem suggested, I probed around with a screwdriver to pinpoint the noise. It seems most load in the upper cylinder area.

I now believe the rattle is actually DIESEL KNOCK. Maybe caused by a faulty or out of adjustment injector.

Also done:
* Checked fuel pressure at the inlet to the injector pump 7 psi constant
* Cleaned the fuel delivery valve at the injection pump
* checked all belts for binding or slap
* removed air filter- same result
* tested the fuel spray pattern- looks very good

Now it just seems we have to wait for a new injector or a place that can rebuild the old one. Nobody can test it locally.


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