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Old 03-15-2012, 08:38:33 PM   #1
aztec
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Lot of Pressure at the gas Cap

Hello I got a 1971 camaro removed all the canister hose on the gas tank and pluged all the lines switch over to a vented cap from a 70 so i wil be able to vent but every time i remove the cap it want to fly out is this normal
or is there some thing els I need to do I dont want to use any of the emisions crap it had on it just all clutter and were all old and rusted Need Help on what i should be doing thanks
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Old 03-15-2012, 09:04:26 PM   #2
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Last time I checked, a '70 gas cap won't fit a '71 gas tank neck.
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Old 03-15-2012, 09:25:35 PM   #3
aztec
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Quote:
Originally Posted by High Country Z
Last time I checked, a '70 gas cap won't fit a '71 gas tank neck.
Thats what they told me at the napa parts store that it was for a 1970 it says (vented/ anti surge) on it
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Old 03-15-2012, 09:28:30 PM   #4
High Country Z
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Do you have the part number?
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Old 03-15-2012, 09:32:46 PM   #5
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Shake the cap and if it's vented, you can hear the check ball rattle inside. It sounds like the cap is not vented if your getting a whoooosh of air shooting out or the ball is not loose.
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Old 03-15-2012, 09:50:04 PM   #6
aztec
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Quote:
Originally Posted by High Country Z
Do you have the part number?
3931449 is what they crossed refrenced it to
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Old 03-15-2012, 09:51:26 PM   #7
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Quote:
Originally Posted by COPO
Shake the cap and if it's vented, you can hear the check ball rattle inside. It sounds like the cap is not vented if your getting a whoooosh of air shooting out or the ball is not loose.
there is some type of ball or something because it does have some play
but like i said it says vented anti slug right on it
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Old 03-15-2012, 09:52:19 PM   #8
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is there another way to vent it not using that cap??
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Old 03-15-2012, 09:55:55 PM   #9
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I connected all the vent line tubes from the tank with gas safe plastic tees,and put a rear differential vent at the end.
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Old 03-15-2012, 11:45:04 PM   #10
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I have a vented locking gas cap that did not vent properly when I bought it. I took it apart and the pressure relief hole was not fully stamped open. Once that was fixed it vented properly.
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Old 03-19-2012, 07:01:04 AM   #11
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Wierd that it is trying to blow out the cap. Usually when I run my car for a while it sucks the cap on as the fuel that is consumed is greater in volume than the evaporating fumes.
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Old 03-24-2012, 02:40:01 AM   #12
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I am watching this thread and curious to see more input. Have read several threads with similar gas cap ventilation issues for those who try to clean up their tank vent lines. Krabben.. did you eliminate the vent line up drivers side into engine compartment to charcoal canister, AND the vent canister located between rear seats? You installed a rear differential vent using plastic tees? Don't suppose you could share a pic or two of that setup? Now just a vented gas cap? No obnoxious gas fumes in your garage? Adams is correct.. if tank is not vented air would be wooshing IN and not out as air would be trying to replace lost volume of gas. Bottom line, a vented cap is probably not 100% adequate ventillation if you plug all other vent lines. There must be a way to handle all this back by the tank if possible w/out fume issues. Surprised this common request has not become a "sticky" fix.
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Old 03-25-2012, 10:19:14 AM   #13
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I capped all of the lines on my 88 truck when I put it together. Then it built pressure and if I remember correctly it was making the check engine light come on. To fix the problem all I did was leave the caps on but took a razor blade and cut an "x" pattern at the end of the cap. This left the cap on but allowed it to vent as well.
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Old 03-25-2012, 06:12:11 PM   #14
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Quote:
Originally Posted by KCardAZ_71RS
I am watching this thread and curious to see more input. Have read several threads with similar gas cap ventilation issues for those who try to clean up their tank vent lines. Krabben.. did you eliminate the vent line up drivers side into engine compartment to charcoal canister, AND the vent canister located between rear seats? You installed a rear differential vent using plastic tees? Don't suppose you could share a pic or two of that setup? Now just a vented gas cap? No obnoxious gas fumes in your garage? Adams is correct.. if tank is not vented air would be wooshing IN and not out as air would be trying to replace lost volume of gas. Bottom line, a vented cap is probably not 100% adequate ventillation if you plug all other vent lines. There must be a way to handle all this back by the tank if possible w/out fume issues. Surprised this common request has not become a "sticky" fix.
I have zero gas fumes in the garage.I put a new tank in,and stripped the car down to its husk.I just connected evrything back at the tank with fuel safe plastic tees,the rear vent,and I think I hung it near the drivers side tank/leaf spring.I'll check for photos and PM you them if I have them.Im pretty sure a few other guys did it here as well.Madmike,Im pretty sure did it too.
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Old 03-25-2012, 11:49:29 PM   #15
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Quote:
Originally Posted by Adams
Wierd that it is trying to blow out the cap. Usually when I run my car for a while it sucks the cap on as the fuel that is consumed is greater in volume than the evaporating fumes.



This is not always true. As the gas sloshes around in the tank it can cause it to build pressure in an un-vented tank. Try putting a couple gallons in a five gallon gas can and shake it around, then remove the cap...........whoooosh, out comes pressure. Allen
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