I was reading my book and found out there is a fuel tank pressure control valve. The valve itself says 30psi and it activates off of the pressure in the tank, I think 30psi in the tank is WAY too much.

Any idea as to what may happen if I just simply removed this valve? It's located like 5 inches before the vapor canister. If removing it is a bad idea how about a way of lowering the pressure it activates at?

BTW, my car is a 91 GTA and it does suffer from the tank pressure that plague so many of these cars.

 

I think the valve is actually rated at 30" WC, which is more like 1.0 PSIG.

Additionally, there is a vacuum pilot line attached to some pressure control valves. When vacuum as low as 3" Hg is applied to the pilot, the valve will open and allow free flow through it with no pressure restriction. The control system will normally apply vacuum to this valve whenever the EVAP canister purge solenoid is enabled, or in the case of older engines, when the throttle is open the appropriate amount and the EVAP TVS is open. If your EVAP control system is connected properly and operating correctly, there should be no more than 1 PSI in the tank when you remove the cap. If there is a problem with a component (like the pressure control valve) the pressure could be significantly higher.

 

I'd like to know more about this

My car has ALOT of pressure in the tank

As soon as I open the cap "WHOOOOSH" everytime, its pretty loud too

Everyone always mentions it if they're standing right there

and every great once in awhile I'll stop at a light and suddenly smell gas fumes for a quick second, then it goes away

i've replaced every vacuum line on the car hoping that would help, and i haven't smelled it yet... but it didn't happen often enough for me to KNOW if the problem is fixed, it would have to stop for like... 3 months, lol.

 

Sorry to bring this from the dead, but i've been wondering the same question.

The originals poster question is not completly answered. I understand that the valve is designed to work with the purge valve, but somehow a lot of people are having issues with the pressure.

I think the problem is that they switched to 2psi in the 90-92. Thats why a lot of those years cars have this issue.

What kind of consequences, if any, would removing the valve (the one located inches away from the canister??).?? I had this issue where that valve was buzzing and i replaced it. Now it only takes LONGER for it to build pressure, but it still does and eventually fuel makes its way to the canister.

I hope someone has some answers for this.

 

nobody has any answers???

 

A bump for ya

I have a question, does anyone have a part number for the valve??? I'd like to purchase one and don't know where to look or what it's called exactly.

 

Yet another bump. According to Tomco, this is a replacement for the OE Evap Canister Vent Valve.

http://cgi.ebay.com/ebaymotors/Canis...mZ150189677748

For future reference: Tomco part number 19015, OE#17087294

My car has been giving me extreme amounts of pressure, I mean, the pump has been squealing from the pressure until I open the cap, let it out, and close it up again. I'm gonna try undoing the clamp at this valve, and see if pressure vents through there. If it does, there's something wrong with that valve.

Oh, and as a sidenote, my parts manual lists part number 17087244 as the correct part for a L98. Which corresponds to Tomco's 19014. *Shrug*

 

Have you checked the canister to see if the charcoal filter has turned into a rock? It used to be you could readily by replacement filters at autozone but I haven't seen them carried there for a long time now. They want to sell the whole darn canister to you instead.

 

I doubt that most owners realize there is a filter (I replaced mine several years ago and it crumbled). IIRC, later cars didn't have it. I bought mine at CarQuest. I have an extra in the garage if anyone requires a part number.

JamesC

 

I don't know what happend to the one in my '85 but it was as if it was coated with shellac over and over and over. That car bit the dust a long time ago though.

 

Just to revisit this again...

What exactly does this valve do, and why does it do it?

I've seen a ton of evap canisters, some with only 2 lines, and some with more than 5. What gives?

I had a problem with my car surging at cruise speeds when the car was warmed up. I disconnect this valve thing and it rides fine now. Though it took me 2 weeks to find that as the issue.

Does anyone have a diagram or write-up of how the EVAP system works?

I can tell what is broken, I just want to know why.

Thanks!