Thread: fuel vent valve

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I have a problem with a fuel vent valve. The guy that built the car mounted it on top of the gas tank. So now every time I fill the tank gas runs out all over the place. When full or expands. Can I just block the line off and drill a small hole in the gas cap? I can not get to the top of the tank to get at valve. I sure don't want to tear the rear out of the car and a
stuff. My gas cap is a solid screw on type gas cap. The motor is a 350 TPI if you need to know that. Thanks in advance!

You could just use a vented cap rather than drilling a hole.
But that won't stop the failed vent from leaking.... Do you store the car indoors? If so, doesn't it smell of gas?


Gasoline can be dangerous. Ignoring the problem can make this a bigger issue.

Sounds like the builder neglected to put in an anti-rollover vent valve, which has a small plastic ball check valve that floats to the top to block off the vent if the tank is over filled, or falls to block in the event of a rollover. It also vents as you fill the tank, keeping it from burping back at you through the filler valve. You need to drop the tank and do it right -

antirollover.jpg

Thanks for the quick response. I just didn't want to drop the tank. Yes, it's parked in a garage. That's why I wanted to do a quick fix. It runs out all the time even going around corners and etc. when full. I thought it was the filler neck. I replaced all that and still leaked. I just jacked up the car and looked and gas was running all over the frame and everything. Looked up and seen a small plastic line clamped to the top of a cross member running back to top of tank. The same level as the top of the tank. Gas pouring out of this line.

Originally Posted by Steel Warrior

Thanks for the quick response. I just didn't want to drop the tank. Yes, it's parked in a garage. That's why I wanted to do a quick fix. It runs out all the time even going around corners and etc. when full. I thought it was the filler neck. I replaced all that and still leaked. I just jacked up the car and looked and gas was running all over the frame and everything. Looked up and seen a small plastic line clamped to the top of a cross member running back to top of tank. The same level as the top of the tank. Gas pouring out of this line.

With an anti-rollover valve, the vent hose is supposed to be run up to the highest point possible and then arced over to form a loop seal. Some like to put a coil in the vent pipe as opposed to simply arcing over into a "U" or "J". You might try extending your plastic line up to a higher point under the car, and then don't top off the tank when you fill. Leave room at the top for expansion as the fuel warms from it's below grade cool temperature to ambient.

If you're not going to drop the tank and do it correctly, then you might want to make sure that your insurance policy includes writing you a check for the value of the car due to fire and that you have a professional appraisal on the car....in writing.

Even with that, you should hope that a good insurance investigator doesn't scan the automotive forums and find that this problem was known to you and the fix was discussed online.

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First off I will try and run the line up higher. I just talked to a fuel tank builder and described what I have. Now, when I move that line I can here a clicking sound. Which he says is the ball on the fuel valve moving but not enough to close it and allowing gravity to open the valve. Do to the line being lower or just at tank height. As for the insurance part. When I get the time to drop the tank I will. I'm disabled and just can't drop it by myself. So, I'm trying to stop gas from running all over for a temp fix so I can get to it when the tank is empty! Don't need a lecture was just looking for help. Thanks

Originally Posted by Steel Warrior

First off I will try and run the line up higher. I just talked to a fuel tank builder and described what I have. Now, when I move that line I can here a clicking sound. Which he says is the ball on the fuel valve moving but not enough to close it and allowing gravity to open the valve. Do to the line being lower or just at tank height. As for the insurance part. When I get the time to drop the tank I will. I'm disabled and just can't drop it by myself. So, I'm trying to stop gas from running all over for a temp fix so I can get to it when the tank is empty! Don't need a lecture was just looking for help. Thanks

You might look at the fittings you have and see how the ball check valve that you're hearing is oriented. It's supposed to be vertical, so that it can "float" upward on an over fill, or fall "down" to seal if you get dirty side up. Sounds like you may just need to re-route what you've got, and maybe extend up as high as you can.

Tech brings up a very good point about forums, e-mails and other social media. The things we say on-line never really disappear, and it's standard these days for lawyers to use special search engines to look for key words when building liability cases, and they routinely search social media sites. It's a new world we live in, and it's not a lecture, just a statement of our sad state of affairs in the modern electronic world.

Hope you can get it fixed right with a simple re-route & extend.

Thanks really appreciate the help. Sorry, it just rubbed me the wrong way. You know how it is when your having a really awful day!

I have fixed similar problems without dropping the tank by pulling back trunk carpet (or other depending location), carefully drilling a 2" - 3" hole using a hole saw, thus accessing the area for repairs. Fasten a sheet metal plate with gasket over it when done and put carpet back in place. To prevent the drill from drilling to far (falling through and damaging below) I use a couple wood blocks under my drill that the drill hits before it drills to far.

Thank you all very much! I'm going to try re-route and extend. If that doesn't work I'll try getting to it under the trunk from inside. Thanks again!