URGENT!! - Is this normal?
Thread Starter
Racer
Joined: Apr 2002
Posts: 353
Likes: 0
From: Tuscaloosa AL
URGENT!! - Is this normal?
Today when I went to fill up the 'vette with gas, I unscrewed the cap and the amount of pressure build-up was quite extreme. ALOT of gas vapor came out with a real heavy rush and for at least 3 seconds maybe more. Is this alright?!? It's just that I never noticed it like this before. We have had some extreme variation in weather here in AL lately but the car is garaged. I just need to know if I have a problem that needs attention.
Racer
Joined: Sep 2004
Posts: 323
Likes: 1
From: Muncie Indiana
Preassure
When you fill the tank the gas is coming from underground where its temperature may only be 50 to 60 degrees. If you filled it clear to the top with very little air space left, and it sat out in the sun at say 80 degrees the gas will expand about 10 o/o. Which builds a lot of preassure in the tank.(20 gallons grows to 22 gallons) This is a closed loop system to keep the vapors from the gas from polluting the atmosphere. If you are old enough you may remember that in the 50's & 60's when you filled your car if you overfilled it and did not leave expansion room at top of tank the gas would flow out of the filler and onto the ground. Therefore we now have systems that do not have relief to the outside until we take off the cap. 
Thread Starter
Racer
Joined: Apr 2002
Posts: 353
Likes: 0
From: Tuscaloosa AL
Locobob - I don't remember it releasing that much vapor the last time I filled up, which was only about a week ago. If there is something blocked in the vapor system, how do I find it? How do I unclog it? Is it safe to drive in the meantime?
Racer
Joined: Jul 2004
Posts: 308
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From: Christiansburg VA
I suppose this offers zero to this discussion; however, when I changed my fuel filter, the next time I pulled the gas cap, I had a similar, several second burst of pressure.
Yall have a good one.
Yall have a good one.
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Race Director
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From: San Jose Pat Tillman - American Hero
Originally Posted by eschoendorff
I have a good amount of pressure under my gas cap when I refill. It's been like that since I got the car.
Team Owner
Joined: May 2002
Posts: 24,337
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From: San Diego , CA Double Yellow DirtBags 1985..Z51..6-speed
Pressure is okay if the car has been parked for awhile, and the gas heats up/expands/evaporates.
BUT, when the car reaches a certain speed, or engine rpm, the fuel vapor canister purge solenoid energizes and allows vacuum to the canister's vacuum valves, which open, and the pressure vents into the intake manifold on the drivers side, (it tees into the pcv line.) There shouldnt be any pressure in the fuel system when you stop at the gas station.
BUT, when the car reaches a certain speed, or engine rpm, the fuel vapor canister purge solenoid energizes and allows vacuum to the canister's vacuum valves, which open, and the pressure vents into the intake manifold on the drivers side, (it tees into the pcv line.) There shouldnt be any pressure in the fuel system when you stop at the gas station.
Burning Brakes
Joined: Oct 2004
Posts: 1,094
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From: West Palm Beach Florida
Originally Posted by eschoendorff
I have a good amount of pressure under my gas cap when I refill. It's been like that since I got the car.
I have the same prob... been that way since I bought it 3 months ago.
Drifting
Joined: Jun 2002
Posts: 1,491
Likes: 6
From: Portland Oregon
Originally Posted by Mark L. Warner
Locobob - I don't remember it releasing that much vapor the last time I filled up, which was only about a week ago. If there is something blocked in the vapor system, how do I find it? How do I unclog it? Is it safe to drive in the meantime?
