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Portable generator engine help.


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Hoping you guys will give this a fresh look with me. I had a customer bring a portable to me last winter, 12 years old but never used ( I believe he had run it but not for years) i drained the fuel, adjusted the valves, cleaned out the carburetor, had to replace the shut off solenoid because it was stuck and corroded. Had it running well on owner supplied gasoline that I believe to have been fresh, no idea about ethanol content. Ran the house with it for about 10 minutes and all was good. 
owner called tonsay it was running poorly and the muffler was cherry red. Took a couple months but he brought it by.  I thought stuck valve but compression test showed 175 in #1 and 172 on #2 i checked valve adjustment which was in spec and replaced a fouled plug which had been new NGK 6 months ago. Had consistent spark from magnetos. Removed carburetor which is a fixed unit with no adjustment, checked function of shut off solenoid, some residue had accumulated in the bowl, cleaned carb with aerosol cleaner which seemed to clean things up Eventually, nothing was visibly clogged but it seemed to become less restricted and solvent was spraying freely through all passages, i blow dried it with compressed air and reinstalled. Drained the fuel in the tank through its filter, replaced the filter and filled with fresh ethanol free gas. Started and ran beautifully for about 30 minutes before falling all over itself backfiring several times and stalling before i could get to it. 
my theory is that it is loosening up residue from the 12 year old gas that had been in the tank. But it doesn’t seem to be clogging filters, it looks clean and fuel is flowing. 
getting quite a bit of time in it and am unwilling to throw a 400 dollar carb at it to see what happens. 
what am I missing here? 

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Just now, Gearclash said:

Does the carb have a gravity fed fuel supply or does it depend on a pump?  If pump, pulse or electric?

Pulse pump and it works

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6 minutes ago, MTO said:

Try running with muffler off

You beat me to it.....mouse condo in the muffler.  :ph34r:

Mike

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6 minutes ago, vtfireman85 said:

Pulse pump and it works

Ok, but is the pump working when the engine quits?  

What happens when you try to restart the engine after it stalls?  

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4 minutes ago, Gearclash said:

Ok, but is the pump working when the engine quits?  

What happens when you try to restart the engine after it stalls?  

Runs like garbage 

 

12 minutes ago, mikem said:

You beat me to it.....mouse condo in the muffler.  :ph34r:

Mike

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Save yourself a lot of time and money and buy one of the $20 knockoffs off amazon. I hate to admit it but those things work great. Just bolt them on and go. Also when I'm doing a carb cleaning I use torch tip cleaners to make sure that there are no chunks stuck in the orifices.

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13 minutes ago, mikem said:

You beat me to it.....mouse condo in the muffler.  :ph34r:

Mike

Easy enough to check I suppose but why would it run great for 30 minutes, and why did cleaning the carb help the first time? 

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Just now, Rawleigh99 said:

Save yourself a lot of time and money and buy one of the $20 knockoffs off amazon. I hate to admit it but those things work great. Just bolt them on and go. Also when I'm doing a carb cleaning I use torch tip cleaners to make sure that there are no chunks stuck in the orifices.

No such thing for a generac i do not believe. They go way out of their way to make everything proprietary. 

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Just now, vtfireman85 said:

Easy enough to check I suppose but why would it run great for 30 minutes, and why did cleaning the carb help the first time? 

Yea, by that time any mouse nest would have been blasted out in a glorious shower of sparks.

And for that reason I don’t think there is a carb problem per se either.  Somehow your fuel supply is getting interrupted.  If the fuel filter isn’t tight enough it could be that the carb is getting the jets plugged.  But I think there is a better chance that the pump is malfunctioning for some reason.  I would try running this engine off an overhead fuel supply and see if it behaves.  

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1 minute ago, Rawleigh99 said:

or the tank vent is plugged.  Run it with the cap loose.

Tank not building pressure, i checked

 

9 minutes ago, Gearclash said:

Yea, by that time any mouse nest would have been blasted out in a glorious shower of sparks.

And for that reason I don’t think there is a carb problem per se either.  Somehow your fuel supply is getting interrupted.  If the fuel filter isn’t tight enough it could be that the carb is getting the jets plugged.  But I think there is a better chance that the pump is malfunctioning for some reason.  I would try running this engine off an overhead fuel supply and see if it behaves.  

fuel tank is overhead it would gravity feed without pump

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6 minutes ago, vtfireman85 said:

fuel tank is overhead it would gravity feed without pump

So if you yank the line off the carb it will whiz fuel without the engine running?

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Just now, Gearclash said:

So if you yank the line off the carb it will whiz fuel without the engine running?

Yes, thats how I drained it

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Just now, busted knuckles said:

I would bet that when it quits, it will not start on starter fluid either. My guess is that one of the coils is heating up and breaking down, by the time you finish playing with the carburetor the coil is cool and it starts.

 

This is a possibility, but then there where 2 problems to begin with, as I don’t think coil fade would cause the muffler to glow.  That sounds like a lean condition.

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Maybe just eliminate the fuel  pump to rule it out. 

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2 minutes ago, busted knuckles said:

I would bet that when it quits, it will not start on starter fluid either. My guess is that one of the coils is heating up and breaking down, by the time you finish playing with the carburetor the coil is cool and it starts.

 

Wouldn’t run stone cold, once the running well deteriorates it wont come back. 

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I am not trying to be difficult, i am just pulling my hair out here, getting to where i have a fair amount of time tied up in this. 

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Just now, yellowrosefarm said:

If the muffler is glowing red, I'd have to agree on it being too lean/ main jet stopped up. What does the inside of the gas tank look like?

Black plastic, hard to tell but it LOOKS clean

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2 minutes ago, yellowrosefarm said:

Does choking it help when it starts to die?

You can nurse it along but it never cleans up. 

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