After filling up the fuel tank for the past couple weeks since I refilled the charcoal canister with aquarium carbon, I can say that the pressurization in the tank is gone. I used to get a "whoosh" of air when I opened the gas cap and that has completely disappeared. 400+ miles later and the CEL has not come back. I think it would have come back by now. The real test comes in four months when I have to pass emissions. Let's see if the fish tank solution is really worth it.
Charcoal Canister Replacement Option
- Thread starter LostAfrican
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LostAfrican is the AC Delco canister still working?
I have the 01 Lexus model, and I've had the pressure build up problem several times. I've worked in the gasoline refining world for 30 plus years, and the amount of vapors surging out of my gas tank gave me the whillies. My thought was that a full tank of fuel would slosh around and get into the vent line and somehow plug things. I don't know if that is what was happening, or not, but I took a page from LandCruiserPhil on the 80 series site and pulled my canister the other day to take a look. I cut the bottom off with a dremel and a hacksaw. I dumped the carbon out and stashed it outside (vapors), took the pads out from the bottom and found two check balls. One in the vent line from the tank in the main section, and another in the small section that went to the intake side of the motor. Taking LCPhil's approach I drilled out the check ball from the tank vent.
I had to work at it a bit to get the line completely cleared going both ways for the gas tank vent port, but after I did, I blew compressed air through every port I could. When I hit the port at the very bottom, I don't know if I blew a membrane or what, but ther was a rather noisy POP, and then the air was flowing out at least one of the other ports well. Maybe the cause of the whole thing???? I don't know. Maybe I broke something. I don't care if the tank doesn't build pressure, it runs the same and doesn't loose gas mileage, doesn't blow codes, and I can pass smog. I probably should have waited to pass my my smog test before messing with this, but I will let you know if I have problems.
In any case, I have the unit in the garage with the epoxy curing, and will put it back in an a few days. Yesterday I went for a quick drive around to see if it would throw any codes without it. It did not.
In ending, I'm not interested in having my gas tank pressurized to dangerous levels, which it has done on three occasions now, with no definitive answer to what the problem even could be. Somehow the vent gets plugged, that is the only way it can build pressure. The check ball is designed to let the pressure out, but not let anything go back into the tank. If that check ball sticks somehow and won't let pressure out, that would do it. I have absolutely no problem allowing gasses back flow into the tank when the tank cools down and draws the gasses backward. Two things: 1) It would just be going backward through the canister and most of that is going to be gasoline vapors, and 2) If any moisture gets through and winds up in the tank, the ethanol in the gas is going to suck it up.
I'm expecting to be rid of this problem, but if any problems pop up, I'll post and let y'all know.
I read a couple of ways to seal the canister, but I use a two part epoxy for restoring wood, and it is less brittle than JB-Weld, and still seems hard as a rock, so I gave it a whirl. We'll see.
I also didn't like the idea of trying to get everything lined up and clamped with the large spring pushing back, so I took the spring out and stuck a couple of screws through the side at the edge with nuts inside to hold the plate down and keep the activated carbon in place. I also just reused the carbon. It looked fine and smelled of gasoline. That's what it's supposed to do.
2001LC
SILVER Star
Any pictures, particularly of the port at the very bottom.
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Just so happens I do. The one pic is the valve in the large compartment, which is the gas tank vent line. If you zoom it, it is noticeably missing (to me anyway). The other picture is the valve in the small compartment and shows the valve with the check ball. There is only one valve there, the others a just reflections.
And fyi, I went for a little longer drive today and pulled the P0440 code, a general emissions error.
I came here for information, then I saw the length of your post and almost skipped it due to its volume of information. WTF is wrong with me?
PabloCruise
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I appreciate the pictures, but I am unclear as to where these are located on the actual charcoal can/box...
PabloCruise
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Do you have pics or a schematic (better yet) of where you were applying compressed air when you got the POP?
Any idea what the connections were to the valve when you caused the popping noise?
PabloCruise
SILVER Star
Did you pull the P0440 code when you were driving around with no charcoal tank installed?
I refilled my cannister., I tried the GM cannister. With both options, CEL eventually came back when it did the next LA4 emissions test and threw a code.
I got tired of it, bought a new cannister, and walked away. Done, no more codes. I've got better things to do with my life, and stuff that I need to do on the Cruiser. I spent days and days mucking around with it, it's just not worth the effort, IMHO.
Buy one every quarter million miles. It's a good deal when you amortize it over 15 or 20 years.
Yes, the cannister was out when I got the code. More on this after answering a few other questions:
Where are the ports? .... If you pull the cannister, it lifts straight up. Turn it over and the bottom is the part to cut off. Once you cut off the bottom, there are a couple of springs, then metal plates, then some padding to keep the charcoal in place. Beneath the padding is the charcoal, and below that is another pad. Remove all of this and the porting is visible and obvious.
The popping?...... The dumb a.. that I am, after emptying the cannister I applied compressed air to all of the port connections without regard to where they were or what they are for. I'm 90% sure it was this port that went POP!!!!,
I would bet that I blew a membrane of some kind, but I really don't know and don't care all that much. If you read more below, I'll explain...
Somewhere above I mentioned that I should have done this after I did my CA smog test, but I didn't, because in the end I just wanted to fix this, so I took a page from the 80 series thread I mentioned, and just did it.
Driving without the cannister in place I got the P0440 code, general emission control error. With the cannister in place minus the check valve I drove maybe 10 miles on a highway with traffic lights, so a little stop and go and up to 65mph, and then got another error. I didn't write this down, but was Lexus specific, and I cleared it pulling into the test station. I was told my catalytic converter and emission system were not ready to read and they asked if I had had a dead battery recently. I didn't, but I did disconnect the day before to clear the computer, and I don't know about these things, but suspect clearing the codes also resets the sensors to the empty state. In any case, I had to do some more driving and take it back, so I bought an inline check valve and installed it in the vent line coming from the gas tank to the the charcoal cannister, which does the same thing as the valve I drilled out. I drove 25 miles or so on and off the freeway, took it back and passed smog.
I'll post more if I get any other errors or pressure build up problems. I may just take the valve out now that I passed smog,
There is a lot of discussion about heat and vapor pressure and ethanol and some other stuff, but in the end it really gets to a major pressure build up inside the gas tank.
Here are a few things I know: (or think I know)
I figure this could only be for one of two reasons: 1) the vent line gets plugged or pressurized the wrong way, or 2) the vent line is too small to allow the gases to escape fast enough.
Most people top off before hitting the trail. I do, and then you wind up bouncing up and down and around with a full tank that sloshes up the filler spout and into the vent line. The vent line runs up, around, down and up again to the charcoal cannister. If it fills with liquid and you get liquid gas in your charcoal cannister I expect the pressure build up there could push back against the one way valve coming from the gas tank and preventing it from venting.
I know that gasoline expands as the temperature goes up, and that when you get your gas from the typical gas station with underground tanks, the temperature of the gasoline could be fairly cool compared to the outside temperature, especially in the desert. So if you start with a warm mid-day temperature, fill up with gas, bounce around, and gain some altitude, there needs to be somewhere for that gas to go if you aren't burning it fast enough. The video of the gas spilling out from around the filler cap is an example, except the the filler cap is only supposed to vent inward and should seal in the outward direction, so a properly sealed gas cap would force the liquid into the vent line, and in turn into the charcoal cannister.
So that's what I know, and as they say for the rest.... I don't know what I don't know,
Cheers,
Joe
PabloCruise
SILVER Star
Sounds like you know a little Joe (in the words of Lynyrd Skynyrd).
I think I will try to go through the FSM and see what the flow paths should be through the respective valves associated with the evap/purge system.
Trying to remember, were you able to run some low pressure air through the line running from the tank up to the charcoal can?
I think I will try to go through the FSM and see what the flow paths should be through the respective valves associated with the evap/purge system.
Trying to remember, were you able to run some low pressure air through the line running from the tank up to the charcoal can?
There are two VSVs, but the only VSV that counts for evap function is the one on the intake manifold. It opens when the motor is running to pull into the manifold the vapors stored in the charcoal canister when the motor was off. It gets gummed up over the years, and it will click like it is opening and NOT open all the way when it gets old, even if you test it with Techstream.
The other VSV only exposes the pressure sensor on the canister for emissions self-test. This one will open when certain testing criteria are met for time and temperature (emissions "LA4" test). This one is why you get emissions intermittent CELs that go away. This one does NOT effect the running function of the VSV, it is only for self-checking for the ECU.
Basically, the whole charcoal and valve system is meant to introduce a vacuum leak into the canister to pull vapors out that were collected while the vehicle was parked, like overnight.
Check the vacuum at the green port under the hood, between the canister and the VSV on the manifold while the truck is idling. You need to be getting good vacuum here before you worry about anything else. If you have a vacuum leak somewhere, you might not be getting enough vacuum to clear out the canister. If you aren't, consider checking/replacing the VSV on the manifold, or fix the leak.
Once that is OK, literally the only thing else to consider in the system is the canister itself.
I was, and it was clear to the cannister and back as well.
PabloCruise
SILVER Star
Warning - virtual wrenching ahead!
I read your post this morning and have been thinking about it while I was working today, so no hands-on time, just thinking (Danger Will Robinson!).
If the line to the charcoal can was clear, and there is only one VSV responsible for evap, then there is the issue of how does the pressure build in the fuel tank?
I am guessing that the charcoal canister is "closed", so there is no constant vent to atmosphere like in the old days when there was a vent line out the bottom of the can. I think this is kind-of backed by your description of the other VSV for diagnostics. The ECU might pull a vacuum test on the can and make sure it sees a vacuum. If I have this correct, the connection to atmospheric pressure would be controlled by that other VSV.
If the tank can indeed vent to the can, but then the can does not get a vacuum source to purge, and also cannot be opened to atmosphere when vacuum is applied, then I think I can "see" how pressure build in the fuel tank itself.
Sounds like a good first step might be to clean the VSV on the intake manifold, yes?
Yes, cleaning the VSV isn't a bad idea. And there is a vent to atmosphere on the canister, but the evap test VSV on top of the canister goes straight to the pressure sensor, if I remember right. Search on my posts and find a bunch of stuff I've written about this process and how the bits work.
PabloCruise
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