Generator makes unusual sound

[engineer bill]

So, we took off on our third short trip to finish sorting out technical issues. We were running the generator for a while and it was making a strange (to me) noise: like Hrumm, Hrumm, Hrumm with a frequency of about 1 cycle/sec. Later on, running it again with the same noise, we powered up our 900 Watt microwave oven and noticed that the microwave's light brightened and dimmed with each cycle. I hope this is not going to be expensive.

[ramit]

most likly just a carberator adjustment or dirt in carb

[DonD]

Lean surge?, richen the mixture.

[DaveVA78Chieftain]

Bill,
First you get the model and Serial No off the generator, post it here so we can decode it.
Then we can ID the service manual which normally has adjustment procedures in it.

Dave

[engineer bill]

Will Do. Sorry for the interval.

[engineer bill]

Here's the info on the ONAN GenSet:


ONAN Emerald I GenSet
1988, 89?


S/N          B890203824
MODEL     4BGEFA26101F
HOURS     835.0

[Stripe]

In the free manual section under onan/service manual you want the one listed as 965-0528

[circleD]

The fluffy dirt build up around the carb indicates a leak of something and it also keeps the heat in. Its not roasting it by no means but a clean genny is a happy one.

[pvoth1111]

Ok that's dirty......it shouldn't look like that ever....don't show that again as there maybe children watching...

[DaveVA78Chieftain]

4.0BGE Spec F
Born February 1989
Fredic pointed to Service manual.  We also have operators, parts, and installation manuals.
To start, turn to page 6-3 (pdf page 57) of the service manual. Scroll down Engine Hunts or surges trouble shooting section.  Begin the search.

Dave

[M & J]

And so the hunt begins to stop the hunting.

[DonD]

Mine did that when I got it. Adjusted the altitude thingy and then dialed in the fuel mixture. Fresh air filter and we are humming.

[engineer bill]

I sprayed a can of generic engine cleaner on the fluffy grease buildup on the carb, and it cleaned up pretty nicely. I was thinking about using just a little bit of brake cleaner to clear off the last bit of filth on the carb adjustment screws, but I didn't. I was a little worried about damage to wiring and hoses from the engine cleaner and the Brake cleaner.


Also, I studied the service manual section on carb mixture adjustment and doing it per the manual is a pretty involved process that starts with a complete setup of the governor and only then progresses to the carb adjustments. Of course I ignored that and went direcly to the carb adjustments:


Because the carb was so obviously out of adjustment I followed the proceedure for gross (initial) adjustment of the main mixture screw and the idle mixture screw. This change stopped the "hunting" immediately. Then I followed the adjustments proceedures (page 6-20). I used a common Kill-A-Watt Meter to read frequency and ac voltage. First the main mixture is set under full load (rooftop A/C on), then the load is removed and the idle mixture is set. It might have been better to use a couple of 1800 Watt hair dryers for the load but, I think the A/C is close enough. I found the frequency and voltage readings to be not particularly helpful as the genset's electrical response to changes (turns) of the mixture screws was not as clear to me as the manual suggests. In the end, I watched the end of the genset exhaust pipe and tuned for smoothest operation. By this time I had inhaled plenty of CO so I wrapped it up and called it a day.


It seems to run pretty good now and the voltage and frequency under load are very close to 120 V AC and 60 HZ. 


Will order the service parts for the oil change and air filter tonight.

[DaveVA78Chieftain]

Good to hear you got it running well again.  Thumbs up!   

[Lefty]

"The fluffy dirt build up around the carb indicates a leak of something ..."

Your spot-on with that assessment. Cleaning the genset is great, but now you need to watch that particular area closely. You should see signs of wetness after you've ran it a while, which should help you determine where that carb is leaking at. It definitely is leaking there somewhere.
A fuel leak is a potential fire hazard... be sure to locate it and get it fixed.
Smart call on not using the brake cleaner... I've found that in most cases it will act as an excellent paint stripper, causing the factory paint to bubble and lift right off.

[Rickf1985]

A lot of carb cleaners will lift off the paint too. My carb is nice shiny aluminum now. W%

[M & J]

I've used brake cleaner many times to clean parts and it didnt remove the paint. Carb cleaner definately will.

[engineer bill]

I will keep an eye on the carb for any leakage but that might just be an accumulation of dirt and leakage from the last twenty-five years.


Any discussion of parts cleaner, carb cleaner and brake cleaner needs to make a distinction between the old school cleaners (pre-environmental damage awareness) and the modern formulations which are something quite different and unfortunately, usually, less effective. Also, there may be differences in formulation of what is availible here in California and what may be available in other places. Awhile back I had to get Cosmoline off of some tapered roller bearings and had the devil of a time doing it in a responsible manner.


Yesterday I poured a couple of pints of SeaFoam into the gas tank and then drove the Winne about sixty miles with the generator running. Now, both the genny and the 454 seem to be even smoother.

[legomybago]

One of our biggest issues with these rigs is they SIT so much. The more often they move, the better.

[engineer bill]

Cleaned up and Adjusted Generator

Note: Summer-Winter adjustment & Altitude adjustment - (two blue green plastic mixture caps over the mixture screws),
idle speed screw, main mixture screw and idle mixture screw. Not shown are the governor adjustments which may be necessary before adjusting the carb.


next up ... oil change with oil filter and air filter.