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Cummins generator diagnosis needed


TN Hillbilly
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Calling @vtfireman85!

Dad has this fairly new, really nice Cummins 5.9 generator.  Power went out yesterday, but his generator never supplied any power, eventually power came back on.

 

I can get it to start and run, engine seems fine.  It will start as it should when the utility service is disconnected.   But it will run a few circuits only, and struggles with them.  (Think flickering lights in a couple rooms, no A/C or fridge.)

I took pictures for you of all the screens on the generator display.  I don't know anything about these, but it sorta looks like plenty of volts but no amps, maybe?

Anyway, we will call for service tomorrow, just wondering what we should tell them.  I'm sure its still under warranty. 

Thanks in advance.

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Can you manually rev it up? Wonder if it "fell asleep". Sometimes they loose residual magnetism and won't put out any power. 10SI alternators are good for that. We've got a locomotive at work that will do the same thing, quick Rev and away it goes.

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The fact that it is putting out close to rated frequency at near rated RPM makes me suspicious of either an issue with the excitation winding an issue with the field winding or an issue with the brushes. I would start by checking connections, however assuming that display is available output not current load it seems like its not generating. Most commonly i find either a bad field boost diode or bad brushes. 

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Something is not right. Voltage looks good. What does voltage do when you apply a small load? If the lights are flickering then the voltage is not fine. The display may not be able to show rapid fluctuations in voltage. Put a good meter on it and look for fluctuations in voltage.

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8 minutes ago, MarkG said:

Something is not right. Voltage looks good. What does voltage do when you apply a small load? If the lights are flickering then the voltage is not fine. The display may not be able to show rapid fluctuations in voltage. Put a good meter on it and look for fluctuations in voltage.

I missed the actual picture of voltage readout. I am

back to loose connection somewhere 

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The screen shots you sent look great. On them there is 0 amperage. Meaning no load. With everything perfect at no load I would guess there is a problem with the engine when you put a load on it. If this thing is diesel then change the fuel filters first and try it again. On most generators the voltage regulator will reduce the voltage when the speed drops off. This could be your problem. Everything is great until you put a load on it. Diesel is bad to grow algae if it sits in a tank unused for long periods of time. The algae will plug the fuel filters and cause the engine to slow under load causing the voltage to drop off. Hence the lights flickering. 
im suggesting you change the fuel filters and figure out how to force the transfer switch to put the house on the generator to test it. If you call for warranty work and the guy comes out to find the filters stopped up he might charge you a service call because filters are your responsibility.

good luck.

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How  much load are you trying to run? Just a few lights? No big motors etc? If so then I doubt that it would be a fuel issue because a few lights is not enough load to cause a partially plugged filter to show up. I'm guessing it is a very loose wiring connection somewhere on the generator output. A 5.9 L genset would be quite a few kw and would not notice a refrigerator starting, much less a few lights. 

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Thanks for all the replies.

This 5.9 is set up for natural gas.  So no fuel filters to change.

Engine runs the same whether I have the house load on it or nothing on it.  1800 RPM either way.

Those readouts are with it trying to power the house, if that helps you.

When you guys say "loose connection" are you thinking internal to the generator, or between the generator and the house?

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32 minutes ago, 12_Guy said:

How  much load are you trying to run? Just a few lights? No big motors etc? If so then I doubt that it would be a fuel issue because a few lights is not enough load to cause a partially plugged filter to show up. I'm guessing it is a very loose wiring connection somewhere on the generator output. A 5.9 L genset would be quite a few kw and would not notice a refrigerator starting, much less a few lights. 

I agree. That’s a 50kw generator. That’s large enough to run 3 or 4 houses. The read out on the gen should come before the breaker on the gen if it has one. Is the generator breaker closed? Check voltage coming out of breaker and at transfer switch. Transfer switch operating properly? If there is a loose connection it will be getting hot. With the lights flickering there is a voltage problem somewhere. Do not try to run ac or any appliances with this condition. The low voltage will burn up your appliances.

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8 hours ago, TN Hillbilly said:

 

When you guys say "loose connection" are you thinking internal to the generator, or between the generator and the house?

It could be anywhere from the transfer switch to and including inside the generator. It will likely be one of the field connections either in the switch or at the generator. It could also be a breaker. Like Mark G said, check voltage. Start at the transfer switch and work toward the generator. You may need to add some load to get it to show up. A resistive load like an electric water heater would be ideal since low voltage will not hurt it. 

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I’m leaning towards the line of answers but if under warranty why not get them out and how competent are you working will electrical? Who did the install?

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Intending on calling the dealer, just looking to have as much info as I can for them before they make the trip out.  They aren't close by, I'd hate for them to come out and it end up being something simple we didn't check.

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Is the transfer switch working properly? Is there voltage at the panel that the generator feeds when the generator is running and  indicates that it has transferred?

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2 hours ago, TN Hillbilly said:

Intending on calling the dealer, just looking to have as much info as I can for them before they make the trip out.  They aren't close by, I'd hate for them to come out and it end up being something simple we didn't check.

I go out on calls that are not equipment or installation failures often enough. It is just part of providing good service to my customers. 

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Well...

Apparently, the big Cummins generator has only a two year (but unlimited hour) warranty.

It was installed in 2018.  So, with a whopping 27 hours on it, this thing is out of warranty. 

Installer is coming to check the transfer switch.  Between you guys, the Cummins tech over the phone, and the installer, we are thinking the problem likely is between the generator breaker and the house, probably the transfer switch.  Dad had a bad lightning storm recently, so it may have been hit.

I asked Cummins about sending someone out, even though it's out of warranty.  He said their only generator tech is FOUR MONTHS out.  I told him thanks, anyway.

So hopefully the installer can find and fix the electrical issue.  Looks like maintenance of the mighty 5.9 now falls to me.  Anybody got a favorite oil for a natural gas 5.9???

 

Thanks again for all the input, guys.  I'll let you know how it comes out.

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38 minutes ago, TN Hillbilly said:

Anybody got a favorite oil for a natural gas 5.9???

Yellow bucket wonder fluid 😉

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  • 1 month later...

So, in case y'all were wondering...it was a loose connection on the breaker on the generator.  It was on the house side of the breaker.  It's working good now.  Thanks for all the good advice and input!

 

Now I'll ask for a little more advice.  Since this thing is out of warranty, I will be taking over the maintenance.  I realize this is probably a dumb question...but here goes.  There is not a drain plug on this engine (5.9 cummins).  In its place is a hose, about 2' long.  On the end of the hose is what looks like an air hose or hydraulic quick connect female end.  (Sorry, not nearby to get a picture.)  I figure this is for some kind of oil pump or vacuum pump used by the Cummins techs to change the oil in this engine.  Now, I could just unscrew the hose and replace with a drain plug.  But in all reality, there isn't room in the generator case for a drain pan or anything under the engine.  So I can't just drain it out.

Do you all have a good guess what kind of pump the Cummins tech would use that connects to that "quick connect" on the drain hose.  Is there a "farmer grade" version of such a pump that I could buy to service this engine?

Thanks, as always!

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If the sump drain is high enough to gravity drain into a pan then it can be as easy as possibly extending the hose beyond the frame and into a pan or jug. If the sump sits below the frame rails, it will be more difficult. I would not be afraid to modify it to work for you without the pump or whatever it was setup to use. Kohlers have a valve and hose threaded into the oil sump. Generacs use a hose with a threaded cap on the end. Either method will work fine. You may have to consider making a hole in the frame that would allow the hose to gravity drain. If so be sure to plug the hole to keep critters out. 

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13 hours ago, brahamfireman said:

Most likely just a quick connect and gravity drain into a pan. Most bobcats are like that,  takes a long time to drain.

The quick connect is probably there so that disconnecting it results in no oil spill. Just remove the disconnect and replace it with a ball valve, put a plug in the outlet side just for safety. It will lessen the drain time. That's what we have on many generators at work where you can't get to the actual drain.

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11 hours ago, TomH said:

The quick connect is probably there so that disconnecting it results in no oil spill. Just remove the disconnect and replace it with a ball valve, put a plug in the outlet side just for safety. It will lessen the drain time. That's what we have on many generators at work where you can't get to the actual drain.

 

On 10/27/2021 at 9:19 PM, brahamfireman said:

Most likely just a quick connect and gravity drain into a pan. Most bobcats are like that,  takes a long time to drain.

What would they plug in to the quick disconnect?  Just a male connector not hooked to anything?  

Tom, I like your suggestion, but I think the disconnect is made onto the hose, not threaded on.  But I will double check that, and replace with a ball valve if possible.

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8 hours ago, TN Hillbilly said:

but I think the disconnect is made onto the hose, not threaded on.  But I will double check that, and replace with a ball valve if possible.

You can always replace the entire hose. Make it long enough to reach where you want it to go. 

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