So I know the topic of whether or not the fuel vent valve or rollover valve (I have heard it referred to as both) can be damaged by boost causing a CEL to be thrown: "Small EVAP System Leak" I believe there is even a wiki on here saying that it is purely myth, and that positive boost pressure will not tear this valve, as there is "no inner rubber diaphragm" I am here to tell you this is false, and I believe the reason this was stated was due to confusion over which valve is the culprit.
Here is a pic of the fuel vent valve which is located under the car near the gas tank. It is pretty much right next to the charcoal canister:
The internal thin rubber diaphragm of this valve will tear after seeing boost for extended periods of time due to its internal shaft design. This will cause a CEL for a "small EVAP system leak" which can be hard to diagnose. As you can see here, a small tear formed on mine:
This pic shows the problem with this valves design. The internal shaft has four protruding sides added for rigidity that have a sharp right angle on the top. When the diaphragm flexes inward from positive boost pressure, instead of being sucked outward in vaccum conditions like it is designed to, it contacts these four sharp corners and eventually tears:
This part is simple and easy to replace and only costs about $13. If you want the new one to last forever, you can simply shave down the four sharp corners on the inner shaft, or you can put a one way check valve on the vaccum line that goes to the top of the valve. That way the valve will only see vaccum pressure.
I have also been told that the small evap canister located behind the front passenger side vent can fall victim to the same fate as it also has an inner rubber diaphragm and sees vaccum/boost from the line going to the TB.
Hope this helps all of you 420A turbo owners out there with this CEL!
1999 Eclipse GS Built motor Hahn 16G Turbo w/ FMIC Hahn Stage 5 Portfueler (270's & 500's) Zeitronix Zt-2 wideband w/ 3.5bar MAP 3" SS Turbo Back CM Stage 4 Clutch and Fidanza Flywheel Baer Big Brake Kit
#128771, "RE: Fuel Vent Valve // Rollover Valve "Myth" Proven TRUE!" In response to Reply # 0
Holy giant fucking pictures Batman!
Erik P. Official 2GNT thread Hijacker Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be... All we know is, He's not The Stig... But he is The Stig's Spartan cousin!
#128773, "RE: Fuel Vent Valve // Rollover Valve /" In response to Reply # 2
Originally posted by Ebster1085 Yea, why the hell are these pics soo big? They do not appear that big if you click on the photo in images. Can an admin resize please? EDIT: Thanks for resizing Tim!
No problem.
Pretty interesting find, I was under the impression that there was no diaphram.
Outside of Corona: "That sucks, peace out..." (jamie walks away)... "Sweeet, what we doin?" -Zac Tim's garage (prior to motor install): "Im gonna smoke real quick, that way if you fuck up I am already nicotined up" -Tim
#128792, "RE: Fuel Vent Valve // Rollover Valve /" In response to Reply # 5
Thank you for taking these pics.
All it takes is two $1 one-way valve's in line with the vacuum lines that go to your evap system/tank, and you should never get an EVAP leak secondary to boost. I made sure to due this before I boosted, and I never had an EVAP code. So easy.
But unfortunately some people have spread false information since then, especially by posting pictures of the rollover valve (which isn't even the culprit) and trying to say that because *IT* is plastic, anyone who says the problem is a valve at the tank is an idiot. This rubber membrane has always been the true underlying issue for the majority of leaks after people start to boost.
2gnt: '99 RS-T, killed by a toyota, pending rebuild... Daily: Volt Daily #2: '99 EVG ebike- STOLEN by PEDRO
#128797, "RE: Fuel Vent Valve // Rollover Valve /" In response to Reply # 6
Originally posted by ez Thank you for taking these pics. All it takes is two $1 one-way valve's in line with the vacuum lines that go to your evap system/tank, and you should never get an EVAP leak secondary to boost. I made sure to due this before I boosted, and I never had an EVAP code. So easy. There have been threads about this where the true culprit was mentioned: http://forums.2gnt.com/dcboard.php?az=printer_friendly&forum=5&topic_id=110945 & http://www.2gnt.com/dc/dcboard.php?az=printer_friendly&forum=5&topic_id=93653 But unfortunately some people have spread false information since then, especially by posting pictures of the rollover valve (which isn't even the culprit) and trying to say that because *IT* is plastic, anyone who says the problem is a valve at the tank is an idiot. This rubber membrane has always been the true underlying issue for the majority of leaks after people start to boost.
I agree with the above mentioned use of a check valve. I did this also. Only I also installed a small vacuum canister and hooked the brake booster and heater controls up also. keeps everything in vacuum all the time.
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99 Eclipse GS turbo: MSpowered, everything custom built, 223.8 HP-199.8 TQ @8psi through auto-tranny. The first time around...
#128815, "RE: Fuel Vent Valve // Rollover Valve /" In response to Reply # 7
That must be the late 98 and 99 Valve. All the early 98 and older have a 100% plastic valve that cannot rupture. If you check the pictures of said Wiki you would see that.
#128816, "RE: Fuel Vent Valve // Rollover Valve /" In response to Reply # 8
Agreed Terry. The older 2G's just have the one all plastic rollover valve which is located on top of the fuel tank. Late 98 and later models have that valve as well as this fuel vent valve that is effected by boost.
Unfortunatly the pics from the Wiki are no longer there, so I just wanted to make sure everone saw this in case they were interested or having this EVAP system leak issue.
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