Everytime I fuel up I feel a force of gases rushing out of the tank when I remove the cap. Is this normal or are these gases supposed to go to some canister? do you guys have this pressure coming out?
If you fill up the tank you are replacing the air inside the empty tank with gasoline. The result is that the air including gasoline vapors will escape from the filler opening. The canister as part of the emission control system will not take care of this.
Here in California at the Gas Stations we have a filler nozzle that covers the filler neck completely if properly inserted. It has the purpose to capture the vapors escaping from the tank during filling.
Thank you for replying goat, it seems is that my tank is pressurized before i begin fueling, meaning once i remove the cap you hear the vapors escape, as if the tank is under high pressure. like relieving a balloon. Its not a little pressure either, my tank becomes very pressurized that you can hear it hissing loud for 2-3 seconds while it releases the vapors. The longer i drive without fueling the more pressurized my tank gets. the vapors coming out while i refuel are silent, and unnoticable. I was thinking something is cloged or not working properly.
Vehicle: SEC 600 COUPE (RHD) One of the chosen few.
Location: Leicester UK
Posts: 1,358
RE: Pressure from gas cap.
Mine always hisses as I remove the cap when it is low quite loud somtimes drawing air in ..not out..
are you sure you are correct in that you get a blow..
not a suck??? it would be the same type of sound.....
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Mine always hisses as I remove the cap when it is low quite loud somtimes drawing air in ..not out..
are you sure you are correct in that you get a blow..
not a suck??? it would be the same type of sound.....
I depend on what side of the world you are. In the UK it sucks and in the USA it blows! "lol"
No joke aside:
I walked out of my shop and tested both the 500 and 600 and Merc600 is correct, it hisses for a short time, but I could not figure out if it blows or sucks.
I believe it would suck, its part of the emission control system. Vapors are supposed to evacuated (creates a negative pressure inside the tank) via charcoal canister and that operates with vacuum or is purged with vacuum. Next time I go out to test it I will light a Match before I open the gas cap to see if it blows the flame out or sucks it in.
so the hissing is confirmed, iam pretty sure it blows out, I will test again tomorrow. I put my hands infront of the gas cap and i just felt a burst of air so i assumed it blew out. My uncles s class had too much vacuum/suction and collapsed his tank. Thats what brought this to my attention in the frist place, dont need to go thru that.
This may actually be a problem with one of your hose (breather hose??) that evacuates the fumes. I had this problem on my 126 500SEC. I'll talk to my mechanic and get the exact term/name of that hose or vaccum line ie the cause of this problem. Double check if your rear passenger can't smell gas.... that's was my symptoms.
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