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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15006
Experience:  Certified on Onan and Generac generators
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I just purchased a 17500watt generac generator. I had it

Customer Question

I just purchased a 17500watt generac generator. I had it running powering a fan motor on a grain aeration system. The generator worked fine for about three hours. I heard the engine stop and went to check on it. Gas was running out of the carb and there was pressure in the fuel tank. I had to open the cover slowly to let the pressure out. When I got the cover off it looked like the gas was boiling in the tank. The engine would not turn over so I pulled the spark plugs the cylinders were full of gas that sprayed out when the engine turned over. What's going on here?
Submitted: 1 year ago.
Category: Small Engine
Expert:  Hank F. replied 1 year ago.

Hello, my name is ***** ***** I am going to assist you with this.

What are the power requirements of the motor on your grain drier?

You stated that the gas looked like it was boiling. Was the gas actually hot?

Did you have the genset in an enclosed area, or was it sitting in the open, with plenty of ventilation?

Customer: replied 1 year ago.
The fan is a 220 volt 5 hp squirrel cage fan with a 24 amp. draw. It was a warm day but the generator was in the open outside and had plenty of ventilation. I couldn't tell you the temp of the gasoline in the tank but it was like a rolling boil in the tank. The tank is a plastic material and it was swollen from the pressure in the tank.
Customer: replied 1 year ago.
We changed the oil in the engine as it smelled like gasoline and the engine restarted and seemed to run fine with no load.
Expert:  Hank F. replied 1 year ago.

Gas in the cylinder and gas in the crankcase are both signs of a bad carburetor - the float is not closing the needle all the way. But in your case, if the tank had that much pressure on it, it could easily have caused that.

I can not come up with a single explanation for the tank to be building up that much pressure, though, unless the engine were just running so hot that it heated the tank up. But if the gas were actually boiling, the tank would have gotten hot enough to melt.

Since this unit is brand new, I highly suggest you get it to an authorized Generac service center for evaluation.