Stihl FS 490 C-M Instruction Manual - Page 9

Sometimes also referred to as "fuel geysering," fuel spraying is an expulsion of fuel, vapors and fumes which can occur in hot conditions, or when the engine is hot, and the tank is opened without allowing the power tool to cool adequately. It is more likely to occur when the fuel tank is half full or more. Pressure is caused by fuel and heat and can occur even if the engine has not been running. When gasoline in the fuel tank is heated (by ambient temperatures, heat from the engine, or other sources), vapor pressure will increase inside the fuel tank. Some blends of gasoline, particularly those designed for use in winter, are more volatile and may cause tanks to pressurize more quickly or create greater pressure. At higher altitudes, fuel tank pressurization is more likely. How to Avoid Fuel Spraying Removing the fuel cap on a pressurized tank can result in gasoline, vapors and fumes being forcefully sprayed out from the fuel tank in all directions. To reduce the risk of burns, serious injuries or property damage from fuel spraying: - Follow the fueling instructions in this chapter. - Always assume your fuel tank is pressurized. - Allow the power tool to cool before removing the fuel cap. - In hot environments, cooling will take longer. - The engine is air cooled. When it is shut off, cooling air is no longer drawn across the cylinder and the engine temperature will rise for several minutes before starting to cool. After the power tool has cooled appropriately, follow the safety instructions in this chapter for removing the cap. Never remove the fuel filler cap by turning it directly to the open position. First check for residual pressure in the tank by slowly turning the cap approximately 1/2 turn counterclockwise. The cap should be held in place by the threads while allowing residual vapor/pressure to be relieved. Once the fumes or vapor have been relieved, turn the cap further until it can be removed from the tank opening. Use only good quality fuel that is appropriate for the season (summer v. winter blends). Some blends of gasoline, particularly winter blends, are more volatile and can contribute to fuel spraying. English Removing the Threaded Fuel Filler Cap WARNING After allowing the power tool to cool, remove the fuel filler cap slowly and carefully to allow any remaining pressure build-up in the tank to release: - While maintaining steady, downward pressure, slowly turn the cap approximately 1/2 turn counterclockwise. - If any significant venting occurs, immediately re-seal the tank by turning the cap clockwise to the closed position. Allow the power tool to cool further before attempting to open the tank. - Turn the cap to the open position only after the contents of the tank are no longer under pressure. - Never remove the cap by turning it directly to the open position. First allow the power tool to cool adequately and then release any residual pressure by slowly turning it approximately 1/2 turn counterclockwise. - Never attempt to remove the cap while the engine is still hot or running. FS 460 C-M, FS 460 C-M L, FS 490 C-M, FS 490 C-M L 7