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Old 05-22-2014, 03:45 PM   #1
BigSix
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Do I have the wrong gas cap?

Just went to take my gas cap off after replacing it recently. First time I have taken it off and there was a good amount of vacuum. I am thinking that maybe I got a non-vented cap by accident? Are we supposed to run vented caps on our trucks? BTW I have the in-cab tank with a V6 and Holley.
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Old 05-22-2014, 03:56 PM   #2
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Re: Do I have the wrong gas cap?

Should be vented...sounds like it's not.
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Old 05-22-2014, 03:57 PM   #3
BigSix
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Re: Do I have the wrong gas cap?

I'm guessing if there is vacuum on the tank that means not vented cap? Would vented mean there is a one way valve to let air into the tank but not let gas/fumes into the atmosphere?
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Old 05-22-2014, 04:19 PM   #4
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Re: Do I have the wrong gas cap?

Quote:
Originally Posted by BigSix View Post
I'm guessing if there is vacuum on the tank that means not vented cap? Would vented mean there is a one way valve to let air into the tank but not let gas/fumes into the atmosphere?
Gas fumes will go into the atmosphere. You will be able to smell gas around the gas cap on a vented gas cap.
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Old 05-22-2014, 09:46 PM   #5
firemanjimtfd
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Re: Do I have the wrong gas cap?

Last 2 I bought at parts store and truck supplier ended up not vented . I took small plastic cap on bottom side of cap and took out spring and rubber check valve. Put small cap back on works now. Cheap fix.
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Old 05-23-2014, 10:26 AM   #6
BigSix
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Re: Do I have the wrong gas cap?

If a vented cap is gonna make me smell gas around the cap then I'll leave the non-vented and just crack it from time to time. Doesn't seem to be much of an issue and I am sure I'll eventually do an engine swap with return line.
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Old 05-23-2014, 01:20 PM   #7
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Re: Do I have the wrong gas cap?

Without a vented cap you may eventually collapse a line or the tank. At a minimum it can cause fuel supply issues. The vent is mainly to allow air in to replace the fuel going out.
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Old 05-24-2014, 12:44 AM   #8
DakotaKid
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Re: Do I have the wrong gas cap?

on a hot day it will also cause vapor lock, fuel will boil a a lower temp n a vacuum.
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Old 05-24-2014, 02:16 AM   #9
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Re: Do I have the wrong gas cap?

Hold it right there...

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