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Gas Cap/pressure in tank problems

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Old 03-18-2009, 07:16 AM
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Gas Cap/pressure in tank problems

I have Pressure/Gas Cap problem...My car smells like gas a lot...I can smell it on the back by the tank...The other day right after I turned the car off...I was trying to smell where it was coming from...and I heard a noise from gas cap....like are pressure was too strong and air was escaping through the gas cap....I took it off and all the pressure scaped out

Should I just buying a new gas cap to fix this problem?? if not....What is causing the excess pressure?

I am also having starting problems and I am thinking its linking to a bad gas cap and not enough pressure in tank due to it.

Please help out with any ideas....Buying new gas cap tomorrow
Old 03-18-2009, 11:26 AM
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Re: Gas Cap/pressure in tank problems

will i cant help you out yet. i have the same thing going on with my car. i also have a line that vents the tank and sometimes i drips. so im looking to fix this but if i find anything out i will let you know
Old 03-18-2009, 11:46 AM
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Re: Gas Cap/pressure in tank problems

you have a gas leak, its not your cap.

I run a vented gas cap on purpose.
Never had a problem with it or smelled anything.

gas cap name brand
Clean-Fill
part # CF 701

Last edited by Gumby; 11-21-2010 at 12:59 PM.
Old 03-18-2009, 02:26 PM
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Re: Gas Cap/pressure in tank problems

There's a tank pressure valve up under the hood connected to the charcoal canister. If it's not working correctly, the gas tank can build excess pressure. I had the same thing going on with my 89 305 TBI, the tank still leaked past the cap after I disabled the cap's ratchet with epoxy. After changing the pressure valve with one from the junkyard, problems seem to have gone away.
Old 03-18-2009, 07:27 PM
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Re: Gas Cap/pressure in tank problems

Originally Posted by Gumby
you have a gas leak, its not your cap.

I run a vented gas cap on purpose.
Never had a problem with it or smelled anything.
I have never seen a gas drop anywhere when its parked...Unless the leak is somewhere around the tank (on the top and it never makes it down )
Old 03-18-2009, 07:29 PM
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Re: Gas Cap/pressure in tank problems

Originally Posted by Al Hasse
There's a tank pressure valve up under the hood connected to the charcoal canister. If it's not working correctly, the gas tank can build excess pressure. I had the same thing going on with my 89 305 TBI, the tank still leaked past the cap after I disabled the cap's ratchet with epoxy. After changing the pressure valve with one from the junkyard, problems seem to have gone away.
any way you could take a picture of this...Please..I would really appreciate it...
Old 03-18-2009, 08:42 PM
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Re: Gas Cap/pressure in tank problems

It's circled down on the lower left. Not very good, but the best I have without going out to take one. This is when I had the motor out of the 92 V6
Attached Thumbnails Gas Cap/pressure in tank problems-p1000695medium.jpg  
Old 03-18-2009, 09:53 PM
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Re: Gas Cap/pressure in tank problems

Originally Posted by Al Hasse
It's circled down on the lower left. Not very good, but the best I have without going out to take one. This is when I had the motor out of the 92 V6
Thanks a lot for taking your time to help out...So you recommendation is to buy a new one and just put it in??...does it just pop in or does it need to be screwed in or closed with a clamp

Thanks again
Old 03-18-2009, 10:08 PM
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Re: Gas Cap/pressure in tank problems

ok om going to apologize for this now. but seeing that we are on the gas pressure.leaking problem. i looked under my car after work today and i have a line comming out from my tank that runs with the rest of the fuel lines. it is about 6" long. where dose this belong to or did the last owner add this for some reason. thanks for the help.
Old 03-18-2009, 10:47 PM
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Re: Gas Cap/pressure in tank problems

IIRC that valve has barbs on the fittings so the rubber tubes don't readily slip off, no clamps that I can remember. On the emissions diagram I found, it's called the tank pressure control valve. I found a replacement in the junkyard and pocketed it while fishing for other stuff. So far I've had no leaks past the gas cap, but I need to put one back on that ratchets to be 100% sure.
Old 03-18-2009, 10:58 PM
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Re: Gas Cap/pressure in tank problems

Originally Posted by Al Hasse
IIRC that valve has barbs on the fittings so the rubber tubes don't readily slip off, no clamps that I can remember. On the emissions diagram I found, it's called the tank pressure control valve. I found a replacement in the junkyard and pocketed it while fishing for other stuff. So far I've had no leaks past the gas cap, but I need to put one back on that ratchets to be 100% sure.
did you have staring problems before changing this tank pressure control valve
Old 03-18-2009, 11:01 PM
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Re: Gas Cap/pressure in tank problems

so that valve goes into the rubber hose that just hangs down? can i get one from a part store or not? and if i put one back in will that fix my problem? i now i have a lot of questions but this is my frist 3rd gen and im not the best with the fixxing the fuel issues that im having. thanks
Old 03-18-2009, 11:18 PM
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Re: Gas Cap/pressure in tank problems

Originally Posted by vargasjc
did you have staring problems before changing this tank pressure control valve
I did not, but then it was a different motor, not the V6. For me it was a free fix from the junkyard. Not saying this will fix your issue either, just an idea that has worked so far for me.


tater7765, I don't know about the tube you have hanging from the gas tank. This valve goes under the hood at the charcoal canister.

Last edited by Al Hasse; 03-18-2009 at 11:34 PM.
Old 03-19-2009, 10:49 AM
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Re: Gas Cap/pressure in tank problems

you won't see any drips unless its allot, there is a heat shield pan under your tank that will collet allot of fuel before it spills over, you will still smell it but not see it.

Do your typical drive, then reach under n bend the corer of that pan down.
Old 03-19-2009, 05:09 PM
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Re: Gas Cap/pressure in tank problems

it is like a small streem for a bit the it is a fast drip. it comes from the tube that runs with the fuel lines, the it stops and i dont know what it goes to.
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