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KaMiKaZeE
11-11-2002, 10:56 AM
Ok, whenever I take my cap off to fill the tank, it makes a loud sucking sound for several seconds until the pressure is equalized. Is this a normal or a malfunctioning gas cap? Please help.
87AccordsterLx
11-11-2002, 11:06 AM
oh crap... mine does that too!!! When I went in to get my emmisions test done my gas cap failed... :( So being that my dad works for NAPA autoparts at thier headquarters we get all parts 1/2 OFF!!!! so a measly gas cap costs $3.00 for a decient one... I would still like to know why it makes that suction though....

Gas Cap
http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=15522755&prmenbr=5806&usrcommgrpid=16543702
DBMaster
11-11-2002, 11:32 AM
It should actually be a pressure release, not a "sucking." But, yes this is normal, especially in hot weather.
KaMiKaZeE
11-11-2002, 03:28 PM
It wont change the air/fuel mix? (carbed)
87AccordsterLx
11-11-2002, 03:45 PM
huh??? air / fuel mix? what does that have to do with the gas cap?
87Hybrid
11-11-2002, 03:55 PM
no it will not affect the air fuel mixture. It is normal.
KaMiKaZeE
11-12-2002, 03:19 PM
I mean as the gas in the tank decreases, if the cap is holding the tank sealed, it should make a steadily increasing vaccum in the tank as there is no way for air to enter to replace the gas that is sucked up. This would cause the mixture to lean out as the tank empties because the increased vaccuum would prevent fuel from being drawn up as quickly, and would eventually stop the flow alltogether when the vaccum is equal to the draw force of the pump. Also, of more concern to me is the possibility that my tank will crumple and implode from the pressure (vaccum). Those are my concerns and what I mean when I talk abt gas cap affecting mix. Also I mention carbed because the pump should be weaker than the FI's thus affecting mix more rapidly. (hypothetically)
pmip
11-12-2002, 03:51 PM
Also, of more concern to me is the possibility that my tank will crumple and implode from the pressure (vaccum).
http://www.imagestation.com/picture/sraid38/p0ce70927b24229e800545b5a6e5c3be3/fd106a44.gif http://www.imagestation.com/picture/sraid38/p0ce70927b24229e800545b5a6e5c3be3/fd106a44.gif http://www.imagestation.com/picture/sraid38/p0ce70927b24229e800545b5a6e5c3be3/fd106a44.gif A gas tank imploding because it's empty!http://www.imagestation.com/picture/sraid38/p0ce70927b24229e800545b5a6e5c3be3/fd106a44.gif http://www.imagestation.com/picture/sraid38/p0ce70927b24229e800545b5a6e5c3be3/fd106a44.gif http://www.imagestation.com/picture/sraid38/p0ce70927b24229e800545b5a6e5c3be3/fd106a44.gif
Grant2k
11-12-2002, 04:05 PM
gas tanks have vents, and a gas cap doesn't seal good enough for that to happen. don't worry.
Neuspeed007
11-12-2002, 07:23 PM
Originally posted by KaMiKaZeE
I mean as the gas in the tank decreases, if the cap is holding the tank sealed, it should make a steadily increasing vaccum in the tank as there is no way for air to enter to replace the gas that is sucked up. This would cause the mixture to lean out as the tank empties because the increased vaccuum would prevent fuel from being drawn up as quickly, and would eventually stop the flow alltogether when the vaccum is equal to the draw force of the pump. Also, of more concern to me is the possibility that my tank will crumple and implode from the pressure (vaccum). Those are my concerns and what I mean when I talk abt gas cap affecting mix. Also I mention carbed because the pump should be weaker than the FI's thus affecting mix more rapidly. (hypothetically)

I agree with kamikazee but i always htough that it was the gas fumes in the car, see i figured that as the gas gets lower in the tank, you start creating fumes in the tank. Because there been times where ive been so low, I KNOW i was running on fumes. Bu it only seems to do it to me when im low. I cant say ive tried it when im half tnk. hehe :) but i htought that when you opened it, that was the fumes being released into the air. But i know it had something to do wiht air pressure. All of you are right, this is just what i thought it was. But its normal! for sure.
dXsquared
11-12-2002, 07:42 PM
it happens when you drive crazy and hit alot of bumps and slosh the gas around lots... try drivin like an old lady for a bit... then open the talk... NOTHIN!! now drive like a racecar driver and open the cap...SSSSSSSSSSSSSSSS........

Travis

If you dont want this to happen, drill a few small holes like 1/4 inch in the cap...
DBMaster
11-12-2002, 07:47 PM
Like I said, it's pressure releasing. That's why you will hear it a lot more noticeably in the summer. It is not a "sucking" sound, but more of a "blowing." (Mega maid's gone from suck to blow!)

There is a spring loaded valve in the gas cap that allows venting after a certain amount of pressure.

In other words, fuh-get about-it.
87AccordsterLx
11-12-2002, 08:39 PM
Travis... umm.. that pic is really nice in your sig... :D :D :D