Generator Leak or Improper Use?

[BobM]

I would like to call upon the collective wisdom of the Born Free Fraternity to assist me in determining the level of my gullibility. I was recently assured by an RV Technician who works for a Generac Authorized Service Center that the leak that I thought I had from my generator was not a leak, but rather an overflow caused by gasoline mixing with oil and overfilling the crankcase-thus the discharge of fuel. (I could smell gasoline in the oil.) The rationale behind this is that if the generator is run without adequate load, the fuel is not burned properly by the generator and the unburned fuel mixes with the oil. (I plead guilty to not always running the generator with a full load.) After the technician changed the generator oil, the generator was run for an hour with the AC and Refrigerator drawing. After the generator was shut off, and we waited for 20 minutes, no leak or discharge was observed. I want to believe the explanation and subsequent result, but something in the back of my head says, this cannot be so.
What say you of the learned Born Free Fraternity? Buy or No Buy? Have I been enlightened or have I been had?

[bcope01]

Bob:

I did a quick search of the web and found this on fuel mixing with engine oil in the crankcase of RV generators:

TURN OFF THE FUEL VALVE (if equipped)

Turn the fuel valve OFF when transporting or storing the generator. When the generator is being transported, the carburetor inlet needle may unseat allowing fuel to enter the engine crankcase. Gasoline will dilute the engine oil reducing the lubrication properties and cause severe engine damage.

The discussion can be found at:

http://www.generatorjoe.net/page.asp?id=48

This might explain the fuel in your crankcase oil. I'm not sure that I'd buy what your technician told you about not running the genset with a load.

In my mind some other situations could cause fuel to spill into the crankcase: 1) if the genset uses a mechanical fuel pump, a hole in the pump membrane could allow fuel to be pumped into the crankcase, 2) a blown head gasket could allow fuel from the combustion chamber to leak into the crankcase, and 3) stuck piston rings, badly scored cylinder walls, or defective piston could allow unburned fuel into the crankcase. However, since the generator ran fine after the oil was changed, I suspect that none of these was the cause.

My guess is that some failure in the carburetor (perhaps the inlet needle described above) allowed raw gas to leak into the cylinders and past the rings. It could be that starting and running the generator "unstuck" things.

There are others in this forum that can probably think of other possible causes.

Bill

[Bill Ruh]

Hi Bob,

I'm not a generator expert, but I am skeptical of the explanation. Small engines (lawn mowers, snowblowers, etc.) are run at high throttle and little or no load every day without ill effects. Is generac really saying that its generators cannot be used when there may be no load? Seems hard to believe.

I agree with Bill that what seems more likely is some carburation problem. Could be when the engine is off (like the needle valve he mentions) or when the engine is on (like a stuck butterfly).

[norijake]

FWIW, standard operating procedure for all the gensets I've owned as well as the gensets owned by friends who were fellow boatowners indicated that you should never operate a genset under a no-load condition. The recommendation was to keep the load at or above 80%.

For that reason and the attending noise and mx of owning a genset, on our last sailboat I opted for no genset, a lot of DC amps, dual high output alternators on the auxiliary and a big inverter; but that's probably a topic for another thread.