Evap Solenoid Delete
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,631
From some reading it looks like the solenoid (located in the back near the passenger side tank is "normally open" so if you remove the EVAP solenoid up front and want to make sure your tank still vents, you can just unplug the rear solenoid and it will always vent through the charcoal canister and the tube that connects to the tanks to each other and back out near the fill tube.
When you start the car, the back solenoid vent vavle closes, and the front solenoid valve does a percentage opening to allow venting/pressure release from the tank as you are driving the car instead.
Also, the car will be taking a Ohm reading of both solinod vavle to make sure it can see them, so when either does not show up during the check since they either removed, it will cause the initial codes to start with.
Last edited by Dano523; Dec 30, 2018 at 01:00 PM.
Drifting
Joined: Jul 2013
Posts: 1,342
Likes: 89
From: Maryland
Originally Posted by Dano523
No, when you shut the car off, the back vent valve opens (after the canistor) to allow the tank to vent cleanly that way, since the front solenoid is closed with the car shut off.
When you start the car, the back solenoid vent vavle closes, and the front solenoid valve does a percentage opening to allow venting/pressure release from the tank as you are driving the car instead.
Also, the car will be taking a Ohm reading of both solinod vavle to make sure it can see them, so when either does not show up during the check since they either removed, it will cause the initial codes to start with.
When you start the car, the back solenoid vent vavle closes, and the front solenoid valve does a percentage opening to allow venting/pressure release from the tank as you are driving the car instead.
Also, the car will be taking a Ohm reading of both solinod vavle to make sure it can see them, so when either does not show up during the check since they either removed, it will cause the initial codes to start with.
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,631
Both back and front EVAP solinoids are just venting lines, and it's not fuel that will be venting through either.
The back one is after the charcoal canistor above the tanks, while the front one vents into the intake instead. Hence idea here, car shut off, venting through the rear canistor as needed. Car started, venting through the front one.
So with back solenoid unplugged to not power up when you start the car, the rear solenoid will remain open, and the tank can vent/pull vacuum as needed though the canister. The downfall to this, is on start up, the system runs a few test to make sure it can see the solenoids (ohm readings) to start with, then quick pressure test of the fuel system to make sure it sealed correctly. So with solenoids disconnected, will need to get codes for the solenoids when they fail the ohm read back tests, as well as the pressure test, and will need to use tuning software to turn off the codes.
The back one is after the charcoal canistor above the tanks, while the front one vents into the intake instead. Hence idea here, car shut off, venting through the rear canistor as needed. Car started, venting through the front one.
So with back solenoid unplugged to not power up when you start the car, the rear solenoid will remain open, and the tank can vent/pull vacuum as needed though the canister. The downfall to this, is on start up, the system runs a few test to make sure it can see the solenoids (ohm readings) to start with, then quick pressure test of the fuel system to make sure it sealed correctly. So with solenoids disconnected, will need to get codes for the solenoids when they fail the ohm read back tests, as well as the pressure test, and will need to use tuning software to turn off the codes.
Drifting
Joined: Jul 2013
Posts: 1,342
Likes: 89
From: Maryland
Originally Posted by Dano523
Both back and front EVAP solinoids are just venting lines, and it's not fuel that will be venting through either.
The back one is after the charcoal canistor above the tanks, while the front one vents into the intake instead. Hence idea here, car shut off, venting through the rear canistor as needed. Car started, venting through the front one.
So with back solenoid unplugged to not power up when you start the car, the rear solenoid will remain open, and the tank can vent/pull vacuum as needed though the canister. The downfall to this, is on start up, the system runs a few test to make sure it can see the solenoids (ohm readings) to start with, then quick pressure test of the fuel system to make sure it sealed correctly. So with solenoids disconnected, will need to get codes for the solenoids when they fail the ohm read back tests, as well as the pressure test, and will need to use tuning software to turn off the codes.
The back one is after the charcoal canistor above the tanks, while the front one vents into the intake instead. Hence idea here, car shut off, venting through the rear canistor as needed. Car started, venting through the front one.
So with back solenoid unplugged to not power up when you start the car, the rear solenoid will remain open, and the tank can vent/pull vacuum as needed though the canister. The downfall to this, is on start up, the system runs a few test to make sure it can see the solenoids (ohm readings) to start with, then quick pressure test of the fuel system to make sure it sealed correctly. So with solenoids disconnected, will need to get codes for the solenoids when they fail the ohm read back tests, as well as the pressure test, and will need to use tuning software to turn off the codes.
Le Mans Master
Joined: Oct 2012
Posts: 9,366
Likes: 969
From: Out back
Can you describe what you did? Any notice in driveability? I don't imagine there is...but it's always good to confirm. No fuel smell in the garage, correct? Did you just cap the lines off?
Last edited by Pb82 Ronin; Aug 22, 2020 at 11:51 AM.
Burning Brakes
Joined: May 2008
Posts: 1,065
Likes: 163
From: Colorado Springs Colorado
2024 C6 of the Year Finalist - Unmodified
To the people that have removed their purge solenoid under the hood, don't you get a gas vapor smell after your tanks heat up? With the front line leading to the intake to burn off vapor stored in the canister, blocking the line will force it out the rear vent, which will put a fuel smell in your cabin. Will it not? I'm diagnosing a fuel smell right now and bought a new purge solenoid, hoping mine is stuck closed. Found this thread researching and couldn't believe people were blocking part of the fuel system which relieves tank pressure, at least I thought it does.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,615
Likes: 4,062
From: Cape Coral, Florida
First off a lot of misinformation in some of the posts above...vent solenoid is normally open and purge valve closed until the PCM requests an EVAP test...fuel tank at a certain level
capacity, certain speed and temp etc...during the EVAP test the ECM will command vent valve closed...purge valve will be opened and burn those fuel fumes (purge and seal) and also start drawing a vacuum...at a certain level ECM commands purge valve closed and ECM looks at a “voltage change”...not a resistance...there is no ohm meter in the ECM !!...vent solenoid remains open at all times until it is commanded close by the ECM...you’ll have to check wiring to purge solenoid if it is suspected closed !!...let by me know if you need help checking the wiring !!
capacity, certain speed and temp etc...during the EVAP test the ECM will command vent valve closed...purge valve will be opened and burn those fuel fumes (purge and seal) and also start drawing a vacuum...at a certain level ECM commands purge valve closed and ECM looks at a “voltage change”...not a resistance...there is no ohm meter in the ECM !!...vent solenoid remains open at all times until it is commanded close by the ECM...you’ll have to check wiring to purge solenoid if it is suspected closed !!...let by me know if you need help checking the wiring !!
Last edited by C5 Diag; Mar 28, 2021 at 09:54 AM.
Burning Brakes
Joined: May 2008
Posts: 1,065
Likes: 163
From: Colorado Springs Colorado
2024 C6 of the Year Finalist - Unmodified
@C5 Diag , could you please take a look at my thread https://www.corvetteforum.com/forums...o-replace.html
I've replaced the drivers side fuel pump, but still get a distinct hot fuel vapor smell if going on a long spirited drive. It comes on like a switch, does not start small and build up. Dealer did a smoke test which I got to witness, appeared to have no leaks or codes.
I'm going to do some testing now. I have put on a new gas cap, vent solenoid, and purge solenoid. I fear it could be the passenger pump or the evap canister....how can I tell given nothing showings in the leak test?
Thanks all.
I've replaced the drivers side fuel pump, but still get a distinct hot fuel vapor smell if going on a long spirited drive. It comes on like a switch, does not start small and build up. Dealer did a smoke test which I got to witness, appeared to have no leaks or codes.
I'm going to do some testing now. I have put on a new gas cap, vent solenoid, and purge solenoid. I fear it could be the passenger pump or the evap canister....how can I tell given nothing showings in the leak test?
Thanks all.
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