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Porter cable generator backfires and cycles


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  #1  
Old 10-31-2013, 08:29:00 AM
noweare noweare is offline
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Default Porter cable generator backfires and cycles

Hello All,
Strange problem with my generator. It is a porter cable 7500 watt generator with a Briggs and Stratton engine.

It runs for hrs with no problems and a good constant rpm. Then it will start
to cycle (varying speed hi & low) and back fire occassionaly. When it does this the output voltage dips and it blows the starter cap on my grinder.

I have taken it in to be repaired and they found no problems with it. I dont think they let it run long enough to see the problem. I use the high octane gas in it because I was told it doesnt gum up.

Anyone have a clue as to what is going on here?

Thanks - Joe
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  #2  
Old 10-31-2013, 09:08:30 AM
I like oldstuff I like oldstuff is offline
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Default Re: Porter cable generator backfires and cycles

Fuel tank not venting and creating a vacuum? Try running it for that period of time with the cap loose to see if it's the issue.
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Old 10-31-2013, 11:53:36 AM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Porter cable generator backfires and cycles

Gas cap vent id check too. You say it runs for hrs no problem then starts to die. If backfiring then I suspect needs a valve adjustment. These small engines dont run well on 92 octane gas. The highest Id go is 89 or regular 87 octane. Higher octane prevents preignition and knocking but requires a higher compression ratio to burn completely. That unburned fuel can be igniting inside the exhaust after it exits the combustion chamber too.

Mid grade 89 octane has better quality control in general, some areas have no ethanol while others have 5-10% ethanol. Ethanol is hydrophilic meaning it absorbs water spoiling the fuel quickly.

Keep us posted Joe
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Old 10-31-2013, 01:24:06 PM
Fred M. Fred M. is offline
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Default Re: Porter cable generator backfires and cycles

Quote:
Originally Posted by noweare View Post
Hello All,
It runs for hrs with no problems and a good constant rpm. Then it will start
to cycle (varying speed hi & low) and back fire occassionaly. When it does this the output voltage dips and it blows the starter cap on my grinder.
Joe-

I wonder if the problem isn't with the generator, but with the grinder?

You might try it with a different load such as an electric heater, and see if the problem is still there.

Fred
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Old 10-31-2013, 04:19:46 PM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Porter cable generator backfires and cycles

agreed on the grinder need to investigate that further perhaps. The backfiring is possibly an improper fuel octane, fuel delivery, and/or possible clearance issue with the valves.
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Old 10-31-2013, 04:26:10 PM
noweare noweare is offline
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Default Re: Porter cable generator backfires and cycles

This time we were using smaller 7" hand grinders not the 220 volt stand up
grinders. It was acting badly for a while before running out of fuel. I added
more gas and it ran good for about a half hour then started it's bad behavior
again.

I took it back to the service center and they are going to run it all day
to be able to see the problem themselves. You know how that goes...
it will probably purr like a kitten all day long : )

I will keep you posted as to what they find, if indeed, they find anything
wrong.

Thanks - Joe

By the way, my local small engine mechanic suggested using the highest octane
gas. He said it would not gum up if it sat for any length of time. That why I am using the high octane stuff.
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Old 10-31-2013, 10:18:25 PM
Bassplayer1985 Bassplayer1985 is offline
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Default Re: Porter cable generator backfires and cycles

High octane gas yes doesn't have nearly as much of ethanol as regular 87 gas. Unfortunately if the engine isnt high enough compression it tends to run crappy.
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Old 11-01-2013, 08:02:28 AM
noweare noweare is offline
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Default Re: Porter cable generator backfires and cycles

Good to know, I will let the service center know I have high octane gas in there.
Thanks
Joe
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Old 11-09-2013, 08:43:58 AM
noweare noweare is offline
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Default Re: Porter cable generator backfires and cycles

The service center is seeing what I see which is good.

They are going to clean the carb. and see if that is the problem.
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