Pressure in gas tank
Thread Starter
Instructor
Joined: Oct 2003
Posts: 147
Likes: 0
From: Holbrook NY
Pressure in gas tank
What is causing my gas tank to pressurize? When I go to fill up, I now get air rushing out of the tank for a few seconds - amazing the gas station attendant, and causing some concern. It is really quite extreme - pressure like that should be used to fill the intake manifold, not the gas tank!
What gives? Is my tank going to explode? A weird fuel pump problem?
George
What gives? Is my tank going to explode? A weird fuel pump problem?
George
Heel & Toe
Joined: Oct 2003
Posts: 24
Likes: 0
From: rolling meadows IL
Re: Pressure in gas tank (George West)
I think that is normal.
When I let the gas run down belwo half mark, it always does that.
It's amazing that it can pressurize the gas tank like that and yet, when it gets less than a 1/4 and at full throttle we still get fuel slosh. :rolleyes:
When I let the gas run down belwo half mark, it always does that.
It's amazing that it can pressurize the gas tank like that and yet, when it gets less than a 1/4 and at full throttle we still get fuel slosh. :rolleyes:
Melting Slicks
Joined: Jun 2002
Posts: 2,168
Likes: 16
From: Phoenix AZ
Re: Pressure in gas tank (George West)
The line to your vapor canister is probably clogged, it's a common problem because the line is metal and small diameter, so it builds up corrosion. Here's a thread I created a while back about how to fix the problem:
http://forums.corvetteforum.com/zerothread?id=416149
[Modified by vetracer, 11:28 AM 10/30/2003]
http://forums.corvetteforum.com/zerothread?id=416149
[Modified by vetracer, 11:28 AM 10/30/2003]
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
Re: Pressure in gas tank (vetracer)
Melting Slicks
Joined: Jun 2002
Posts: 2,168
Likes: 16
From: Phoenix AZ
Re: Pressure in gas tank (tjwong)
It is normal. all the newer systems are completely closed and relies on the EVAP system to vent the system of the fumes.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Pressure in gas tank (George West)
What is causing my gas tank to pressurize? When I go to fill up, I now get air rushing out of the tank for a few seconds - amazing the gas station attendant, and causing some concern. It is really quite extreme - pressure like that should be used to fill the intake manifold, not the gas tank!
What gives? Is my tank going to explode? A weird fuel pump problem?
George
What gives? Is my tank going to explode? A weird fuel pump problem?
George
The round coffee-can looking canister near the driver's side headlight is a vacuum controlled vapor charcoal canister controller by a solenoid for venting fuel vapor from the gas tank.
Since the gas cap is of the unvented type (to keep gasoline vapor out of the atmosphere) if the solenoid is inoperative or one of the canister vacuum hoses is off/leaking, the gas tank won't vent and pressure will build.
I'd start by tracing the vacuum hoses to make sure they are all connected and in good condition. The solenoid is right at the cannister(but not part of the canister) and should have two hoses attached to it.
There are three hoses coming off the canister (at least on my 86 there are) the hose that is by itself is the one leading to the gas tank. The other two go to the solenoid then (as a single hose) to manifold vacuum.
I remember that my hoses were very dry and brittle, had cracks and were leaking vacuum.
Hope this helps.
Jake
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Safety Car
Joined: Feb 2002
Posts: 4,212
Likes: 10
From: Sun City West Az
Re: Pressure in gas tank (BluByU)
where is the Charcol Canister on LT1's?
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
Re: Pressure in gas tank (ittlfly)
i cleaned out the CCP line tonight.. it was loaded with crap! only took a few mins.. i think it helped.. i did note when i went to fill up with gas that it was a vaccum not pressure when i took off the gas cap.. is that normal?
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Pressure in gas tank (BluByU)
I think VetRacer touched on that a few responses up. I believe he's correct.
Check it a few times over a period of, say, a few days after the fill up and especially after the car engine has run for a long while. The condition may be more prevelant when the gas level is low.
I try to never get lower than 1/4 tank, so I haven't noticed that condition with my car.
Jake
Check it a few times over a period of, say, a few days after the fill up and especially after the car engine has run for a long while. The condition may be more prevelant when the gas level is low.
I try to never get lower than 1/4 tank, so I haven't noticed that condition with my car.
Jake
Melting Slicks
Joined: Jun 2002
Posts: 2,168
Likes: 16
From: Phoenix AZ
Re: Pressure in gas tank (BluByU)
i cleaned out the CCP line tonight.. it was loaded with crap! only took a few mins.. i think it helped.. i did note when i went to fill up with gas that it was a vaccum not pressure when i took off the gas cap.. is that normal?
Race Director
Joined: Nov 2000
Posts: 17,103
Likes: 39
From: stop the fun suckers
Re: Pressure in gas tank (vetracer)
on the LT1 there is a hose from the CCP purge solenoid along the front passanger wheel well do near the windshiled washer resevor where it conn ects to a hard plastic line.. disconnect the rubber line throw it on the flow and roll it with your foot the whole length.. this will break up all the crap.. then use compressed air to blow it out (even the air pump at the gas station would work)
goodluck! :cheers:
goodluck! :cheers:
Thread Starter
Instructor
Joined: Oct 2003
Posts: 147
Likes: 0
From: Holbrook NY
Re: Pressure in gas tank (BluByU)
Thanks y'all!
Right on the money. There is no conduction from the my gas tank to the charcoal cannister. Vetteracer - thanks for an excellent tech tip. I know the trouble now, although it is not quite fixed yet. The repair is now trivial - the diagnostic advice was priceless.
George
Right on the money. There is no conduction from the my gas tank to the charcoal cannister. Vetteracer - thanks for an excellent tech tip. I know the trouble now, although it is not quite fixed yet. The repair is now trivial - the diagnostic advice was priceless.
George
Melting Slicks
Joined: Jun 2002
Posts: 2,168
Likes: 16
From: Phoenix AZ
Re: Pressure in gas tank (George West)
Thanks y'all!
Right on the money. There is no conduction from the my gas tank to the charcoal cannister. Vetteracer - thanks for an excellent tech tip. I know the trouble now, although it is not quite fixed yet. The repair is now trivial - the diagnostic advice was priceless.
George
Right on the money. There is no conduction from the my gas tank to the charcoal cannister. Vetteracer - thanks for an excellent tech tip. I know the trouble now, although it is not quite fixed yet. The repair is now trivial - the diagnostic advice was priceless.
George
BTW my fuel tank pressure problem has never reared it's ugly head since. :cheers:
