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Guardian Portable Gasoline Generators Questions, Answers, and Information About Gasoline Powered Portable Guardian Generators

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Old November 13th, 2011   #1
JIBLANE
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Default Backfire on shutdown

I wonder if others have had this problem. I have it on a Generac GP7500E brand New. Seems to run great maybe slighty fast? Voltage is perfect startup is perfect just on shut down I always get a backfire. So now I just shut the fuel valve off and let her shut down that way. Do i need an idle adjustment or will that screw up my voltage/ Not sure?
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Old December 2nd, 2011   #2
fsd62
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Default Generac GP7500 Backfire issues

My neighbors and I just purchased a total of 3 Generac GP7500E generators and they are all backfiring on shutdown. We purchased them through ******* Power systems over the internet and they were shipped factory direct from Generac. Neither company has been any help answering my questions and keep "passing the buck" The bottom line is that we too would like to know why this is happing and how it can be corrected. Are their others with newly shipped units experiencing this same issue? Is this a safety issue? Is this a design flaw or just an adjustment needed. I will be continuing to try and get an answer from from one of the Generec service centers but unfortunately the closest one to me is over an hour away and I have not had much success over the phone. I will update this Thread if I have any additional information. Any additional help or information that anyone could provide would be greatly appreciated.
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Old December 2nd, 2011   #3
rthacker7
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I have a GP17500 and always shut mine down by removing load, wait for a cool
down and turn fuel off. That way there is very little to no fuel left in the carb.

I don't know if the GP7500 has a fuel solenoid om the carb or not but in general
,without one , when ignition is shut off and the motor coasting down raw fuel gets into the muffler. Fuel in a hot muffler ignites and causes a fairly loud pop.

A lot of the larger small engines do that if the mfg, did not put a fuel solenoid on the carb. The solenoid shuts fuel off at the main jet so no fuel to motor, no fuel
in muffler and no pop.

If Generac did not make provisions then adding one is probable not possible.
I see it a lot on small tractors. Is it a design flaw--no. Is it a safety issue--no
Can you adjust it out--probably not, at least I would not try.

If your generator has an idle switch you might try letting it run for a few minutes on idle, sometimes the muffler will cool down enough they won't pop.

A lot of motor mfg. leave the solenoid off as a cost savings, as the solenoid is not real cheep, and can be a problem as they age.

Just trying to explain what happens, anybody got anything else

RonT
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Old December 3rd, 2011   #4
fsd62
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Hi Ron,
Thanks for your response and information! I got a lot more help from you than I did from either of the two companies that I had mentioned in my post. Overall we are very happy with the Generac GP7500E. It seems to be a very well made machine with a good dependability track record from what I have been told. We purchased these units for emergency backup power during outages. We are in NJ and have had two major storms over the last few months with sustained power outages.
I took your advice and used the fuel shutoff instead of the power switch and no backfire. Im glad to know that this is not a manufacturers defect or safety issue on this run of generators from the factory.

Thanks again for taking the time to reply to my post!!

Scott
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Old December 18th, 2011   #5
JIBLANE
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Fuel shutoff thats also how I now shut it down. Idling didn't help I also contacted Generac and they just gave me a list of service places. I don't believe it will be an issue. Power output seems perfect runs and starts great. Seems like it idles fast but as far as I remember most Generators I've used in the past at work seem to run about the same.
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Old December 18th, 2011   #6
fsd62
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Thanks for your post. I have also found our generators idle a little fast but only without a load so that must be by design. I have test run my unit several times and I am very happy with it overall. As suggested, I now use the fuel shutoff to avoid the backfire.
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Old December 18th, 2011   #7
Dave_eng
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Another benefit of running the carb dry besides no backfire is having no fuel in the carb will make starting easier in the future. The more volatile components of gasoline, the ones which make starting easier, evaporate in the carb as they are exposed to air. This leaves behind the less volatile stuff and starting is tougher. The gasoline in the tank is less exposed to air and experiences less evaporation of the lighter hydrocarbons so when the carb refills after you open the fuel valve you will have a fresher fuel to ignite. I advise friends who dont have a backfire problem to physically drain the carb after use to accomplish the same results.
Dave p
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Old December 26th, 2011   #8
Matt
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I had the backfire on shut down as well. I then started starving it of fuel and it stopped. Now I run the GP7500e on natural gas and have to shut the fuel down to shut it down so I don't have that problem.

http://www.youtube.com/watch?v=CLIXJo_YyQs
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Old December 27th, 2011   #9
JIBLANE
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Wow I didn't know you can do that will it work with Propane? If so whats the cost and work involved to change over. i have two hundred pounders of propane tanks I could leave filled and ready to go wonder how long that would run the Generator??
Interesting stuff
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Old December 27th, 2011   #10
Ginaelectric
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Shutting off the fuel supply is how any gasoline small engine should be turned off, It drains the carb of fuel so that it does not give the Ethanol a chance to rot out the carb and gum up the jets.
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