Generac generator (natural gas) starts but won't stay running

[Clare Snyder]

How old is this thing??? What engine? Might - possibly - be worth putting on a new fuel system - - -?

[Sterling]

My generator is a older model generac generator i think it was built in the 90s it was in storage for about 20 years or so a friend of mine had it and gave it to me . The problem i have with it is when it starts it runs for about 7 seconds then it dies each time i start it and i wondering what's the problem can you guys help me out here.

[trader_4]

First place to start, put a meter on it and see if you get correct voltage while it's running. When it starts up it checks for voltage and if it's not correct, it shuts down. If this is a natural gas model, that's the most likely cause.

[Marilyn Manson]

Has it ever worked for you? You say your friend gave it to you, but I can't tell if that is just extra info. Has it actually been 20 years since it was last started?

What kind of fuel? How was it stored? Was the fuel left in it? Have you cleaned the carburetor?

How are you setting the choke? If it's warm out and you set/leave the choke on full, it may stall soon after starting. (When my snowblower is warm, I have to set the choke at halfway to start the engine but then immediately turn off the choke to keep the engine running.)

How's the oil? Many generators will shut down if there is low oil pressure. Champion (I know you said Generac) claims that the sensor can stick to the bottom of the crankcase and "think" that it is low on oil. They are talking about new units, but I could see that happening after 20 years of storage. You could try disconnecting the sensor to see if that helps.

More details might help us help you.

[Marilyn Manson]

I've never checked the voltage of a generator within the first 7 seconds. Is that enough time for the voltage to settle down and be considered stable?

When it's cold out, it might need more than 7 seconds before the choke could even be turned off. I don't plug anything in until my generator is running smoothly with the choke fully off.

[Dan Espen]

In the subject line, it's natural gas.

I had a natural gas pool heater. It would turn on, run for a few minutes, then turn off. There was a safety feature, if the heater didn't sense sufficient heat being produced, it would turn off, wait a few minutes and try again. I had to replace the temperature sensor.

Other wild guesses: Insufficient gas flow. Old gas in the line, give it multiple tries. Cobwebs clogging the orifices.

[Marilyn Manson]

The OP (and I therefore assume the subject line) is from 2013 from an OP named TOM.

This post is from today (3/3/2022) from Sterling. I chose not to assume that he was asking about the same type of generator. Safer to ask and get an answer from the person that asked the most recent question.

Old natural gas in the line? I didn't know that that was a thing. Not saying it isn't, just never heard of it.

As far as multiple tries, seems like he has tried that, but granted, he doesn't say how many times.

"it runs for about 7 seconds then it dies each time i start it"

I wonder how many 7 second tries it take to get old natural gas out of the line, assuming it is natural gas.

That could be an issue.

[Clare Snyder]

Get a gas technician out to check the regulator/converter/vaporizer unit. For some reason it is likely not passing fuel. On a Generac heap it could be just about anything else too - the low oil shut-down switch is a known buggaboo on many of their products.

[Dan Espen]

I was envisioning this thing outside somewhere with a long gas line leading too it. Yeah, probably not very likely.

I have a friend with a generator that runs on propane which burns a lot hotter than NG. Maybe this thing has a NG/Propane adjustment?

[Jacob Jones]

It wouldn't be overheating that quickly.

[trader_4]

My comments were in the context of a Generac natural gas generator, the thread was titled that way, but the poster who revived this old thread didn't say what exactly it is that they have. The Generac natural gas standby generators are the ones that will shut down after about ten seconds if the control logic does not detect proper voltage. I know, because I too got one for free via a neighbor. That one was only maybe five years old. Knowing the symptom, I figured maybe it was just a bad senor, like for oil pressure, that was the problem. I obtained the service manual online and figured out what was going on. The generator section was not producing voltage, causing it to shut down. Looked like it was a bad rotor, but I didn't have the right test equipment to be able to fully check the stator. And then while looking for the cost of parts, I found a huge number of terrible reviews on Amazon for the Generac standby generators. Everything from them arriving new leaking oil, to firing up regularly for the weekly test, then failing after a couple of hours when needed. That's what happened to the one I was given. Even though it was relatively new, the service guys told the owner it was not worth fixing, he bought another one.... So I dismantled it, sold some salvageable parts on Ebay and sent the rest to the scrap yard.

The typical portable generators AFAIK don't have this kind of shutdown check. Also, if they are gas powered, then you have a carb that's a prime suspect too. With the natural gas with no carb or fuel system to foul, if it starts and quits after ten seconds, the most likely scenario is that it's being shut down because the voltage isn't there. Plus it's a very easy thing to check and one that most people would not even know about.

Can't help but tell they Ebay story. One of the parts I listed was the engine, which looked like new. Listed it for $300, for local pickup only. It was up for a month or so and a guy in Puerto Rico contacts me and asks if I will sell it to him if he arranges shipping and pickup. I said sure, but it's not crated, I'm not going to figure out how to do it, etc. He says no problem and buys it. So later the shipping company contacts me and I make sure they understand that it's not in a crate, it's not packed. They were surprised. Some time later, they contact me again and arrange a day and time to get it. Nobody shows up. I contact them and they finally come, couple of guys in a van, they just haul it out and off they go. In the process of all this I exchanged emails with the buyer, in the end he tells me that while he was quoted like $300 to ship it from NJ to Puerto Rico, they actually changed that to $700 and that was before they picked it up. That didn't exactly surprise me. I told him you should have just told me that and I would have given you a refund. He said he's a man of his word, so he went through with it. If it was me on the other side, I would have offered the seller $50 or so for their trouble if they would cancel the sale.

The other thing, you would think with these generators failing all over the place that it would not be too hard to find an engine from a local dealer in PR instead of getting one from here. This was about a year before the big hurricane down there. I hope he got it and it worked for him through that, in which case I guess it makes it a lot better.

[Denny]

It'll start then flashes over speed

[Ronfox]

My generator does exactly the same thing. Generac same model

[Chester Oakley]

Is it single phase or two phase?

[Dean Hoffman]

I learned something again accidentally. There is some literal two phase left in the United States.

It's obsolete and might not be changed out. Some commentary and pictures from Mike Holt's forum.

[hubops]

I worked at a 25 Hz. station in my youth - Ontario Power GS - right at the foot of The Falls :

25 Hz. was finally completely phased out - in the late 1980's .. if I remember .. John T.