Check Gas Cap Warning -
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Unread 10-18-2009, 09:01 PM   #1
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Join Date: Oct 2009
Location: Illinois
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Check Gas Cap Warning

I have had this damn check gas cap light haughting me for awhile now. I have bought two different caps and hasn't solved the problem yet. I have reset the computer and got rid of it for a couple days but it is back. I am thinking aftermarket gas caps suck.....I am going to try to hit the junk yard and find an original. Does anyone know how to turn this warning off for good?

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Unread 10-18-2009, 09:31 PM   #2
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Be aware that the system monitoring the evaporative emissions system (which includes the gas cap, the charcoal canister, purge valve, etc) is "guessing" it's a gas cap based on the volume of the leak. It's entirely possible you could have a leaky hose somewhere in the system that is leaking at the same rate as a typical gas cap leak. Best place to look is at the ends of the hoses where they attach to the charcoal canister or other parts of the system - it's pretty common to find hairline cracks at the hose ends.
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Unread 10-18-2009, 09:41 PM   #3
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I have gotten the warning once, but it was on a day were there was a a big drop on the tempeture, I have never seen it again...
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Unread 10-18-2009, 10:07 PM   #4
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When you put your filler cap back, how tight do you do it?

My wife's 2005 Verona Owner's Manual sez to "click" it 3-5 times to make sure it's tight (we click it once. I don't like to overdo it, and there are people I hear at the filling station who crank the thing down. Once it clicks, it's tight enough. You don't want to break the ratchet - I usually charge $20 to remove it after that.)

Even a new cap won't seal if it's not tight enough. And, your rig probably isn't old enough to have a problem with the EVAP hoses.
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Unread 10-19-2009, 06:07 PM   #5
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2013 WK 
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Mine was on when I bought it. It turned out to be a disconnected vacuum hose under the Hemi shroud under the hood. The guy who fixed that hose left another one off when he was done. I wanted to see for myself so I took a peek and saw it from the drivers side when I looked under. I took the plastic off and replaced the hose and all was well. If yours is a Hemi, be careful when you take off the plastic cover because it pulls and touches a lot of stuff under there.
05 Grand Cherokee Limited 5.7 Hemi 265/65/17 Revos, K&N
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Unread 03-30-2015, 04:17 PM   #6
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I just replaced gas cap with OEM. Noticed that my vapor canister was damaged. just installed another. connected hoses, however I have a question. Hose going to check valve didn't have a clamp. I am still getting damn check gas cap warning on dash! Should I clamp big hose to check valve? Also, hose that snaps to lower connector doesn't seem to be very is snapped into place. I am just wondering if I should clamp both?

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