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Discussion Starter #1 (Edited)
I have a Generac Guardian Series 15kw generator (Model 043902). It’s an older system.

Recently, the propane supply was disconnected and reconnected. Ever since then, the generator sounds very different during the exercise mode and the ON mode. When it turns on during the exercise mode, it sounds like there are continuous fluctuations in its cycling. When the generator is in ON mode, it sounds normal, like it always sounded before during the exercise mode and ON mode.

I am linking two audio files -- the normal ON sound and the sounds during the exercise cycle. Does anyone have an idea as to the issue and whether I should be concerned about it?

Exercise Mode Sound - Clyp

ON mode sound - Clyp

Would appreciate any thoughts. Thanks.
 

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check the fuel filter screen for the lp.
almost sounds like air or vapor in the high pressure fuel line system.

where was the line disconnected at?
was it on the high pressure?
or at the low pressure?
do a line purge.
and check the filter.
and air filter too.

it is doing it in the low speed mode... maybe a dirty lp valve in the system.
not letting enough fuel for the low speed.
 

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As far as I know running is running, the weekly exercise is just a scheduled run. If disconnecting the LP line caused a rough run, it’s likely purged of any air and good to go at this point.
 

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I hear ya. He didn’t state it if happens every time it “exercises”. Just that it happened and that under normal operation it ran fine.
 

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I would test the AFR on the exhaust...
that would show what is up for sure...
as well as use a spark tester
click here for the test tools page
if it is a twin cyl be sure to get two or one for each cyl.
that way you could get a visual on the spark during run.

there are just 3 basic things for combustion.
air, fuel and spark.
and lots of little things in there as well.
if it is over fueled on lp or ng it will loap as well as miss if it is under fueled.
that is where the air fuel ratio comes in.
we ran in to this on the direct injection of NG for the honda gx 390.
it is a pretty wide band on lp.. and more narrow on ng.
getting it perfect so it will ramp up and down is the trick.

and it does need engine pre heat on the LP fuel in the vaporizer.
ng works better above -20 deg f.
so as long as you have a bit of air box pre heat on both ng and lp , you are set.
take a lesson from the diesel industry for that.

yup tricky finding issues on the auto run gen gear.
if you do not have the oem scan tool.
wish they would make a blue tooth tool for ois for all of the can bus as standard on all gen sets.
 

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Discussion Starter #7 (Edited)
Thank you both so much for your replies. To clarify, the "loping" happens all the time during the exercise mode. The connection was taken apart and reconnected near the tank. Unfortunately, I do not understand many of the words used in your replies, nor am I capable of performing the various steps you have suggested, nor do I have the tools mentioned to perform testing.

With my layperson's knowledge, I do understand the concept of "running is running". I guess my main question is whether it's critical that I pay someone to figure out the problem or whether to let it go since it is working ok on the ON mode. Does loping during the exercise cycle generally indicate that there is some significant problem that needs to be addressed promptly?
 

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Hmmm, so it always sounds weird in exercise mode and never when its simply turned ON? Does your model generac have the Low Speed Exercise mode? Low speed mode runs the generator at 2400rpm instead of 3600rpm to reduce noise, wear, and fuel consumption. Even at low speed it shouldn’t sound likes it loping. Itd be weird to have only a low speed fueling issue but something to look into.

Have you tested the generator with the house being powered by the unit?
 

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Discussion Starter #9
Thanks for your reply, drmerdp. Before the propane tank was disconnected and reconnected, the exercise mode always sounded the same as the ON mode, so I don't think the exercise mode is supposed to be low speed. The power to the house seems steady when the generator is on.
 
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