Evap System Problem/Question
Evap System Problem/Question Guys,
After a lenghty cruise a couple weeks ago with temps in the mid 90's I unscrewed the gas cap to fill up and the pressure was overwhelming. It releaved pressure for atleast 3-4 seconds and was pretty forceful flow of fumes coming out of the filler neck. I've checked the lines to and from the purge solenoid to the char canister and everything is clear and flows freely. The lines are good and there is no vacuum leaks, but can I test the purge solenoid somehow to make sure it's functioning properly? Also, I'm getting no codes.
Lastly, is there anywhere else I could check as the tank should not hold that much pressure? Thanks and any advise is appreciated.
After a lenghty cruise a couple weeks ago with temps in the mid 90's I unscrewed the gas cap to fill up and the pressure was overwhelming. It releaved pressure for atleast 3-4 seconds and was pretty forceful flow of fumes coming out of the filler neck. I've checked the lines to and from the purge solenoid to the char canister and everything is clear and flows freely. The lines are good and there is no vacuum leaks, but can I test the purge solenoid somehow to make sure it's functioning properly? Also, I'm getting no codes.
Lastly, is there anywhere else I could check as the tank should not hold that much pressure? Thanks and any advise is appreciated.
Since I have forgiven you for chewing my *** out for selling a use throw out bearing on the board several years ago, I will now gladly respond.
If you are confident the line from the canister is clear (which I doubt), the issue must be the solenoid not opening like it should. If you take the solenoid off, you should not be able to blow air through it. Once you apply 12V DC to it, you should be able to blow air for it. Most of the time, there is charcoal from the canister clogging the line from the canister.
If you are confident the line from the canister is clear (which I doubt), the issue must be the solenoid not opening like it should. If you take the solenoid off, you should not be able to blow air through it. Once you apply 12V DC to it, you should be able to blow air for it. Most of the time, there is charcoal from the canister clogging the line from the canister.
Since I have forgiven you for chewing my *** out for selling a use throw out bearing on the board several years ago, I will now gladly respond.
If you are confident the line from the canister is clear (which I doubt), the issue must be the solenoid not opening like it should. If you take the solenoid off, you should not be able to blow air through it. Once you apply 12V DC to it, you should be able to blow air for it. Most of the time, there is charcoal from the canister clogging the line from the canister.
If you are confident the line from the canister is clear (which I doubt), the issue must be the solenoid not opening like it should. If you take the solenoid off, you should not be able to blow air through it. Once you apply 12V DC to it, you should be able to blow air for it. Most of the time, there is charcoal from the canister clogging the line from the canister.
Okay, got an update. Pulled the Charcoal canister and all looked good, no charcoal and lines are clear all the way from the tank to the purge solenoid in the engine bay. The solenoid works just fine as I put 12v to it and it opens/closes just fine. Also, the evap pressure control valve connected to the charcoal canister works just fine and flows. I replaced all the hoses as they were pretty dry rotted, but I'm still unsure why the tank is pressurizing so much? Could the low vacuum from my cam cause the EVAP system to not work very well? As that's the only thing I can think of?
TECH Apprentice
Joined: Oct 2010
Posts: 341
Likes: 18
From: Colorado
Im not sure of your exact problem, but I know that my car builds a lot of pressure when its hot out and has anything below a full tank... I have replaced the charcoal canister with an AC Delco unit, blew out all the lines, tested/cleared out the EVAP solenoid and have checked all the lines at the sending unit... I think that maybe the valve at the tank/canister might be bad?? Not sure yet.
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Im not sure of your exact problem, but I know that my car builds a lot of pressure when its hot out and has anything below a full tank... I have replaced the charcoal canister with an AC Delco unit, blew out all the lines, tested/cleared out the EVAP solenoid and have checked all the lines at the sending unit... I think that maybe the valve at the tank/canister might be bad?? Not sure yet.
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Joined: Jul 2013
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I have a similar problem on our 1997 Trans Am convertible. We have tested all the lines, replaced the canister, the evap solenoid and the evap switch. Been to two different shops, both said it was fixed, in both cases the CEL came back on within two days. We are at our wits end trying to figure out why we still get the same P0440 error code. We've also replaced the gas cap 2 times.
I just posted on an old thread about this today....
I have the same problem, except worse. To the point where I can't fill with gas, unless I relieve the pressure by sticking a tube down into the gas tank. (It feels like I have to push back against a check valve). I haven't gotten as far as anyone else here to diagnose the problem, but the only last thing I can think of to check is: The fuel tank pressure sensor? Maybe the ECM isn't seeing pressure, so it doesn't send a signal to open the purge valve.
That's all I can think of.
The purge valve gets a fast pulse from the ECM to operate, so I'm not sure that responding to a steady 12v is enough to know it works right. And I don't have the equipment to test the signal going into the purge solenoid. And I sure as hell don't know if I'm ready to get to the pressure sensor in the gas tank.
I have the same problem, except worse. To the point where I can't fill with gas, unless I relieve the pressure by sticking a tube down into the gas tank. (It feels like I have to push back against a check valve). I haven't gotten as far as anyone else here to diagnose the problem, but the only last thing I can think of to check is: The fuel tank pressure sensor? Maybe the ECM isn't seeing pressure, so it doesn't send a signal to open the purge valve.
That's all I can think of.
The purge valve gets a fast pulse from the ECM to operate, so I'm not sure that responding to a steady 12v is enough to know it works right. And I don't have the equipment to test the signal going into the purge solenoid. And I sure as hell don't know if I'm ready to get to the pressure sensor in the gas tank.
