Engine on generator runs rough

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  #1  
Old 04-09-14, 12:44 PM
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Engine on generator runs rough

I have a Generac (7kw Corepower) generator on our home. It is powered by a single cylinder 15 hp engine running on natural gas.

The generator and engine are housed in a plastic box with removable sides and lid for servicing. The engine pulls air thru a channel in the lid to feed the carburetor.

If the lid is on the engine runs rough - stumbles. If i remove the lid it smooths out and runs normally. If i place my hand over the air intake and partially block the air flow, the engine runs rough.

My only thought at this time is that the air flow is too restrictive thru the lid.

Has anyone else had this issue? I've called Generac, but they do not do any trouble shooting over the phone. Our local Generac service guy is a long way away and is not responsive to my calls.

Any suggestions? Thanks!
 
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  #2  
Old 04-10-14, 09:57 AM
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The choke is completely off - the butterfly in the carb throat? Is there an air filter on the intake and if so is it clean and up to date?
 
  #3  
Old 04-10-14, 04:59 PM
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Thanks for your response. I can't see the choke because of the air intake housing, but i can see the linkage and when i move it, the engine basically dies - so i think the choke is working properly.

The air filter is essentially new - the gen probably has less than 15 hours of run time and the filter looks brand new…

I removed the air filter and it ran fine until i put the lid back on and it immediately ran rough.
 
  #4  
Old 04-10-14, 05:19 PM
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The thing that comes to mind with something like that is this:

The fuel feed through the carburetor is metered with a baseline determined from the reservoir for fuel in the carburetor. This is controlled by a needle valve/float or needle valve/diaphragm type.

The final supply of fuel to the engine is designed then with a certain amount of vacuum at the filter end of the intake. Any resistance to the air flow entering the carburetor before the carburetor will make the mixture richer because the engine draws harder on the air flow, so the draw on the fuel supply in the carb increases = richer mixture. This is why you set carburetor mixture screws with the filter in place.

If all is good with the filter and the intake passage, then the fuel supply inside the carb must be off. If you have an all position carburetor it would be at the diaphragm fuel reservoir or if a fixed position carburetor at the float/needle valve or possible a possibly a loose jet.

That's all I can think of. A course of action would be to clean and put a kit in the carburetor.
 
  #5  
Old 04-11-14, 10:33 AM
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Thanks again for your response. I'll do some checking to see what kind of carb is in this gen.
 
  #6  
Old 04-12-14, 09:32 AM
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I made it sound a little more complicated than it actually is as far as type.

The fixed position is what you'd find on a lawn mower - those would have a float bowl, although a lot of them now have a diaphragm pump to help with the delivery of fuel to the carb.

The all position would be what you'd find on a chain saw or weed wacker.

You surely have the fixed position with the float bowl. The problems with those, other than cleaning are usually a leaking float valve or bad float.
 
  #7  
Old 04-12-14, 02:59 PM
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The engine pulls air thru a channel in the lid to feed the carburetor.
And...
If the lid is on the engine runs rough - stumbles. If i remove the lid it smooths out and runs normally.
And...
My only thought at this time is that the air flow is too restrictive thru the lid.
BINGO!
If the engine runs well when the lid or sides are removed yet stumbles when the lid and sides are properly closed then it is obvious that there is a problem with the air channel in the lid. Have you checked to see if this channel is clear and unobstructed?

It is too bad that Generac is not responsive to the problem but I would first check the air channel and if clear then I would add some more air intake openings.
 
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