Fuel Tank Pressure; solutions needed
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Fuel Tank Pressure; solutions needed
My '95 has lots of pressure present whenever I loose the fuel tank cap.
I have pulled the vent lines off the canister and used compressed air to blow from canister to the purge valve (disconnected from solenoid first).
Had pressue in the line from the tank to canister.
Checked that vacuum check valve was working. Had flow in only one direction.
After all of this I still have lots of pressure in the tank. Even from just sitting due to air temp warming-up.
Is the probelm the canister itself? Do these clog-up?
How is this system supposed to work anyways?
I have pulled the vent lines off the canister and used compressed air to blow from canister to the purge valve (disconnected from solenoid first).
Had pressue in the line from the tank to canister.
Checked that vacuum check valve was working. Had flow in only one direction.
After all of this I still have lots of pressure in the tank. Even from just sitting due to air temp warming-up.
Is the probelm the canister itself? Do these clog-up?
How is this system supposed to work anyways?
Last edited by LannyL81; Mar 31, 2007 at 09:31 AM.
Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
I thought this fuel tank venting system was supposed to vent the gas fumes into the intake instead of the open air. So I understand that the fuel tank could build-up pressure when the car is just sitting, but once running...then there should not be any pressure in the tank.
But going to fill-up and there is pressure in the tank. This is what does not make sense to me. My '96 does not seem to build-up anywhere near as much pressure.
I guess the vacuum solenoid on the intake could be defective and not venting the tank to the intake....have to check that.
But going to fill-up and there is pressure in the tank. This is what does not make sense to me. My '96 does not seem to build-up anywhere near as much pressure.
I guess the vacuum solenoid on the intake could be defective and not venting the tank to the intake....have to check that.
Instructor
Joined: Sep 2006
Posts: 220
Likes: 0
From: Castleton NY
Before I pulled the engine on my 87, I never noticed it. After I did my engine and eliminated my vapor canister, it had the pressure. I didn't like it and pulled the rubber O ring/seal on the gas cap to let it breathe. I smell no fumes (inside or out) and there is no more pressure. If I notice fumes, I'll put it back on, but so far...no worries.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
One of those things that's probably better to observe than to try and sort out here. Some pressure is normal and will vary with temp and really abnormal would be a geyser when you unscrewed the cap. Canister can get satuated with fuel, but that leads to a crappy running engine. I'd take it to a shop, maybe even a Dealer, let the service mgr observe it and then decide if it's anything to be worried about.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
o-ring
ODI,
The o-ring is to make sure that if your gas filler box fills up with water during a rainstorm, the water doesn't flow into your tank, contaminating it with dirt and water
The o-ring is to make sure that if your gas filler box fills up with water during a rainstorm, the water doesn't flow into your tank, contaminating it with dirt and water
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Thread Starter
Melting Slicks
Joined: Nov 2005
Posts: 3,323
Likes: 142
From: Green Valley Arizona
Road Agent:
Not sure know if it is a vacuum or a pressure....never took the fuel cap off and felt whether air was coming out or going in..have to do that today.
But still have the question as to why I have so much pressure or vacuum building up?
Take it to a dealer....no way...have yet to find a shop that takes any pride in their workmanship here in Tucson. Get it out as fast as possible and don't worry if there are left-over parts... It would be nice to have a trusted shop.....
Not sure know if it is a vacuum or a pressure....never took the fuel cap off and felt whether air was coming out or going in..have to do that today.
But still have the question as to why I have so much pressure or vacuum building up?
Take it to a dealer....no way...have yet to find a shop that takes any pride in their workmanship here in Tucson. Get it out as fast as possible and don't worry if there are left-over parts... It would be nice to have a trusted shop.....
Instructor
Joined: Sep 2006
Posts: 220
Likes: 0
From: Castleton NY
Yes...that was one of the considerations before taking it off Coupeguy. But, it is a garaged car and I really don't drive in the rain. Should I get caught in the rain...or should it take on water when washing...the drain should do it's job. Even if it doesn't drain...it doesn't look like much water gets in there anyway because of the fuel door cover. Supposing the drain stopped working and a lot of water still got in...the cap overlaps the filler neck....it would have to be submersed back there....and I'd probably need fuel (and notice) before it became a problem. I am keeping my eye (and nose) on it!!
Last edited by ODIVETTE; Mar 31, 2007 at 11:42 AM.