brian43
I have a model 0043892 generator. it starts but runs very rough. if i remove the tube running from the air box to the valve cover (?) the engine picks right up and runs fine. if i then replace the tube, the engine begins to rev up and down. i'm no expert but it seems like it's not getting enough air.

I've read earlier posts discussing similar symptoms (with different models) and have noticed recommendations of bending choke plate (don't know what this is or where it is on my model) or replacing the air box.

Any ideas? I've got new spark plugs properly gapped, new battery and new bellows.

The engine was tuned up last year, i never checked it as i trusted this guy, but recently noticed it wasn't perfoming weekly test. not sure how long it's been out.

thanks.
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brian43
please help!
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bronco
I assume this is a new problem. If you look behind the battery you will see the gas regulator. On the regulator you will see a brass adjustment screw. With the engine running turn the gas adjustment till the engine runs smooth. If you can't get it to smooth out remove the stop pin and readjust.
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brian43
thanks for the reply. tried to adjust the gas regulator, smoothed out a bit but not great. if i turn the screw too far the engine begins to rev up and down (am told the governor spring is pushing the throtle down). still runs much much better w/o air filter or if i remove the hose running from the valve cover to the air box. can i run w/o the hose - if i plug the opening to the air box? or can an air filter that looks brand new not be? thanks for any help.
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78buckshot
It would'nt hurt to put in a new filter if your in doubt about the last service, might make all the difference.
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brian43
thanks i will try a new air filter. i also notice that the "repair" man who last sericed the machine replaced the spark plug with a champion plug - rc14yc - not a generac. could this be contributing to the rough running?
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78buckshot
The champion 14yc is the factory replacement plug in the maintainence kit, check the bellows between the air filter box and the throttle, also the breather tube from the valve cover to the air box. These parts deteriorate with age and cause hard/no starts, rough running, etc.
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brian43
thanks for the reply. i have a new bellows and the air tube seems fine (clean, solid). but the machine runs much better w/o the breath tube on. can i run the machine w/o that tube?
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78buckshot
You could block off the port at the air filter box, and the hole in the valve cover, then try running the unit. The breather tube from the valve cover is designed to keep pressure from building up in the crankcase of the engine, also it helps to reduce the amount of condensation in the oil and crankcase. If the engine runs better with the tube removed vs. the tube installed, something is wrong in the fuel/air side of the system.
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brian43
thanks again for the advice. i've replaced the bellows, air filter and spark plug. i've also adjusted the regulator. it still runs rough, or when it gets too much gas pushes against the govenuer. the engines runs much much better when the tube from the valve cover is removed and more air is allowed to enter the air box. you suggest a problem with the fuel/air side but what could it be? i'm not a mechanic but what other things could cause this problem? thanks for any insight
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bucdup
Is the unit running on LP or Natural Gas? Have you checked gas pressure static/running/load? Is there a secondary regulator at the generator? If so, I have seen where the vent for the regulator is blocked or buried or whatever. The best way to tell if that is a problem is to loosen the cap for the adjustment screw on the back of the regulator. If your gen smooths out you either have a bad regulator or blocked vent.
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brian43
my generator runs on NG. the regulator isn't buried, it's housed w/in the unit. i don't see a vent or a cap to loosen the adjustment screw, just 2 plugs on the front. generator is model 43892. the engine seems air starved. could the regulator be bad? there is a solenoid of some sort on the top of the regulator, can that fail? or is there an oxygen sensor of some sort?
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Skip Douglas SkipD
brian43;10312 wrote:
my generator runs on NG. the regulator isn't buried, it's housed w/in the unit. i don't see a vent or a cap to loosen the adjustment screw, just 2 plugs on the front. generator is model 43892. the engine seems air starved. could the regulator be bad? there is a solenoid of some sort on the top of the regulator, can that fail? or is there an oxygen sensor of some sort?
Have you checked the natural gas pressure at a point outside of the generator housing (the delivered gas pressure)? That would be a very logical step #1.
Skip Douglas
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johnc
To continue Skips post. Take the gas pressure readings at as many places as possible. Before the regulator, is your house supplied with hi or low pres. gas, read after the regulator most likely at the inlet of the gen's solenoid valve and at the outlet of the solenoid valve. If the regulators vent is not working, the static pressure on the outlet side will be ok. But when gen. running, pressure will be low. Cause the diaphragm in the regulator cannot work.
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brian43
i don't know about the gas pressure but everything worked fine in the past - can the pressure change? as for the vent in the regulator being blocked, i would like to check that but don't know where to look. where is it located?
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Skip Douglas SkipD
brian43;10393 wrote:
can the pressure change?
Regulators definitely can fail if that's what you're asking. The only way to know if your gas delivery system is behaving as designed it to MEASURE its performance.
Skip Douglas
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genme
SkipD;10394 wrote:
The only way to know if your gas delivery system is behaving as designed it to MEASURE its performance.
For someone who is competent, what gauge would you recommend for NG and LP?
Model 5875, Nexus controller, 999cc Engine, 20kW LP, 2011
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Skip Douglas SkipD
genme;10395 wrote:
For someone who is competent, what gauge would you recommend for NG and LP?
I use a water-filled manometer made by Dwyer. Click on this link for a [url=http://www.dwyer-inst.com/Products/ManometerIntroduction.cfm][U][COLOR=Blue]primer on using manometers[/COLOR][/U][/url]. There's no meter movement to possibly get buggered up due to rough handling.

One can easily make their own manometer using a board, a ruler, and some flexible plastic tubing. A home-made one could be just as accurate as the one I use.
Skip Douglas
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johnc
This has been discussed before. A dail type manometer is fine, but drop it, go buy another one. In an emergency situation and it does not read what it should, is it accurate or is the needle sticking? What do I have to compare the reading to? My choice for the occasional homeowner who is competent with tools. Get a water manometer. It's cheaper. Fill it up with water when needed to use, when done, empty the water. Will last a life time and is accurate enough. Amazon.com -water manometer- general tools hg15- $ 28.00 .. Yellow jacket # 78060 gauge manometer $46. Water manometer make sure you get 0 to 15 inches water column, some may only go to 0 to 8 inches water column.
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78buckshot
For those of us that work with propane and natural gas, we carry several gages. I use my refrigeration gage at the primary LP regulator to adjust it to 8-10 psi, then I use a dial gage at the secondary reg. to adjust to the 12-14 in. w.c. range, then at the appliance, generator in this case, I use a U-tube water manometer to fine tune either natural or LP, typically 11.5 in. w.c. for LP and 7 in. w.c. for natural.
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78buckshot
Hey brian43, check the air inlet tube/duct from the outside rear cabinet to the filter box, maybe it picked up some leaves or other debris and is restricting the combustion air.
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brian43
78buck, the air intake tube is clean and clear. i guess i'll have to have the regulator performance measured as suggested by skipd. but i'm hoping soemone could describe the regulator vent as many have mentioned. i'm looking at the regulator and don't see anything that i think to be a vent.
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78buckshot
You are running on natural gas, most likely you have a regulator at the meter or built into the meter. You also have the regulator inside the generator, each of these regulators need to breath or "vent" from the back side of the diaphram to the atmosphere in order for the diaphram to move. In your case it sounds like the generator is getting too much fuel so I doubt that the vent/vents are blocked, everytime I have found a blocked vent it was LOW or NO gas flow that led me to check the vent. You should have the gas supply checked for correct size pipe and static pressure and running pressure, then you can go from there. I'm betting the problem is not outside the generator.
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