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Genset load issue

Discussion in 'Technical Discussion' started by Capt Bill11, Mar 30, 2019.

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  1. Capt Bill11

    Capt Bill11 Senior Member

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    Genset issue:

    2-3 year old 40kW NL gensets with close to 8000 hours on then.

    Recently service on injectors and injector pumps. They run fine.

    Problem:
    If the load on either unit gets much passed 100 amps the unit lugs down and can’t handle the load so the second unit has to be brought online and the load split.

    The boat apparently had the same issue with the original gensets which were Kohler 40kW units.

    Thoughts?
  2. MBevins

    MBevins Senior Member

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    Off the wall maybe but by chance are the fuel lines undersized?
  3. Pascal

    Pascal Senior Member

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    Lugging down under load is usually fuel starvation. I m sure you ve checked the filters so maybe there is a restriction in the fuel lines, manifold or return

    We sometimes trip the breaker on the Onans 27.5 but even at 100 amps they don’t bog down
  4. Lepke

    Lepke Member

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    It also could be an exhaust restriction or incoming air restriction. Muffler too small, too much water going thru the exhaust, sound enclosure incoming air too restricted, air temp in the engine room too hot.
    Whatever it is, it affected two different models.
  5. Capt Ralph

    Capt Ralph Senior Member

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    What color is the exhaust when you have the issue?
    Can you smell any thing in the exhaust? Unburned fuel, or acid odor?
  6. Capt Ralph

    Capt Ralph Senior Member

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    I have witnessed clogged fuel lines from debris settling in the fuel lines or restricting fittings. I have started blowing lines out with nitrogen when this is suspected.
  7. Capt Bill11

    Capt Bill11 Senior Member

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    This problem is on a friends boat.

    The weird part is everything mentioned here has be looked at and eliminated.

    The only time there was a slight increase in there ability to handle a bit higher load, but still not anywhere near there limit, was when one of the gens was run by feeding it fuel from a bucket via an electric pump with the return line going to the bucket as well.

    That’s when electric pumps were added with no real improvement.

    It seems like a fuel delivery problem. But they can’t figure out why.

    The injector pumps are going to be looked at again.

    But.....
  8. Pascal

    Pascal Senior Member

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    Weird that both injection pumps would have a problem at the same time unless rebuilt to the wrong specs. Fuel restriction in a fitting?
  9. MBevins

    MBevins Senior Member

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    Once had a similar problem with a main. Turned out that the inner liner of the huel hose separated from the outer skin. When a certain load was reached the inner liner collapsed and let the starvation begin. After the load wad removed it popedp back out.
    Took a while to find that.
  10. Pascal

    Pascal Senior Member

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    Racor issue maybe causing a restriction. I wonder if a vacuum gauge Teed in right before the genset wouldn’t help diagnose a hose , valve or primary issue
  11. PacBlue

    PacBlue Senior Member

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    Some older Racor’s have a ball in the bowl by design, could be adding to a restriction issue. Volvo Penta used to require them removed on certain engine models.
  12. Danvilletim

    Danvilletim Senior Member

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    We have a 53kw kohler that would drop the load. Engine would keep running and an auxiliary fault light comes on. We spent 12k rebuilding the power making end and first night in Bahamas it drops the load again after an hour. The other 53k runs great and powers the whole boat.

    Ideas?
  13. Pascal

    Pascal Senior Member

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    What happens next? Reset the breaker? Shut it down? Works right away or has to cool? What does the guy who charged you $12k say?
  14. Capt Ralph

    Capt Ralph Senior Member

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    My aft tank pickup tubes had screens with goo over them.
    Time for a vacuum gauge and maybe some clear hose looking for air.
  15. Capt J

    Capt J Senior Member

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    What about the fuel vents? Have them open the fuel tank fill (s) and see if that changes anything.
  16. captholli

    captholli Senior Member

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    Swap the regulator and power boost module out from your good 53 kw to your faulty 53 and see if it holds load.
  17. PacBlue

    PacBlue Senior Member

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    Sounds like a good question for K1W1?
  18. Danvilletim

    Danvilletim Senior Member

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    So we are back at the dock and can’t get the thing to drop the load. This ability to not embed able to reproduce it makes it difficult.

    It has dropped load st anchor and underway. Any ideas? If there any way to test/read max output other than turning on stuff?
  19. Pascal

    Pascal Senior Member

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    I ll ask again... what is needed for it to work again? Let it cool off, shut it down, reset an error code, reset a breaker ??? Will it restart and work right away?
  20. captholli

    captholli Senior Member

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    A local Marine Electrical company like Bishop Marine Electric or Fine Line Marine Electric will have a carbon pile load bank available to connect to your gen for load testing. I still feel that your Control circuits i.e. / voltage regulator and power boost module are the culprits here with thermal heat failures. Intermittent failures like your reporting are hard to find but proper troubleshooting is just a matter of process of elimination. You might want a thermal camera to scan your alternator connection box and components for high heat signal spots in cable lugs, winding tap connections etc. that could be loose and drawing high amperage on one leg or another prior to your rectifier causing your control electronics to go to default.

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