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Anyone else getting a loud hiss when unscrewing their filler cap off when filling up.Mine will give a loud hiss as it's being screwed off like there is a vacuum in there. I'm not getting any symptoms of fuel starvation to the engine as the tank is being emptied and fuel used, just find it strange as I thought there is usually a vent in the fuel cap that prevents this type of thing.
 

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Yep every time I open it I get a hiss from a vacuum!
 

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I don't recall hearing a hiss from a vacuum, but it could be because I don't hear well or I'm used to it.
 

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That's part of the emissions control system. The fuel tank is kept at negative pressure so that gasoline fumes stay inside. There's a charcoal canister that absorbs vapor when the tank warms and the vapors in the tank expand. As the tank gets drawn down, fresh air gets sucked back through it to return the vapors to the fuel tank. It's why you get a CEL if your filler cap is loose.
 

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The snakes are coming out this time of year. Some of them bite; carry a can of snake repellant for these occasions. If they do get sucked into the engine, they will reduce the octane level somewhat. Then you'll hear knocking. Careful; that means the snakes got arms (the hydrocarbons are a Genesis accelerant).
 

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The snakes are coming out this time of year. Some of them bite; carry a can of snake repellant for these occasions. If they do get sucked into the engine, they will reduce the octane level somewhat. Then you'll hear knocking. Careful; that means the snakes got arms (the hydrocarbons are a Genesis accelerant).
Over here in North Carolina the Spiders are coming out!!! But if they get sucked up they go right through....don't seem to have an effect on engine knock!!! Smell a bit funky though....
 
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