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Vapor Canister Help

CDW6212R

Hauls the mail.
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Well done, thoughtful and documented. Others will appreciate your efforts as they find this thread in the future. That problem is a rare kind, but older cars do have odd issues.
 



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Drewmcg

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2002 XLS 2WD
Thanks. Another update. Not content to leave well enough alone (or to wait for several successful re-fills), I found a thread mentioning a TSB for a different model/year Explorer. It mentioned a problem with water gettng into to vent hose because of a failed connection between the hose and the fuel filler housing. I know that this was not my problem, but bear with me a bit here . . . .

Evidently water is bad karma for vapor canisters and other evap system parts. The TSB mentions checking the fuel for water. I don't remember exactly why, but I do recall a few months ago dumping two cans of alcohol/water absorber into the gas tank. I've run lots of tankfuls of gas since then, and even ran the tank down to 0 (in line for the pump at Costco; another guy helped me push the truck up to the pump!)--so I know I don't have water in my gas. (If it matters, I have the Flex fuel engine K.)

Another part of the TSB caught my eye. It said if that there is any water in the tank, replace the evap purge solenoid. Then I thought about it. When that solenoid duty cycles on, it pulls a strong vacuum through the evap line--into the intake manifold. If there is any water in a canister or line (or water vapor)--it would get sucked right through the purge solenoid.

On the test drive I mentioned above (before the successful fill), I monitored the fuel tank pressure sensor (volts) and tank pressure (inches of mercury). The tank was about 3/4 full. I wondered if I might have a bad sensor (not sure why). Anyway, it was jumping pretty wildly, every second or so. Tank pressure was between 0.70 down to -(negative) 10.0 inches. Seemed wild to me, but maybe PCM was doing a evap test. I don't know what normal readings are, though the tank's normal pressure range is supposed to be, but the sensor's normal (KOEO) control volts are supposed to be around 2.69 volts.

Anyway, I had a spare purge solenoid from a donor, lower-mileage truck with no mouse chewing history, so I pulled it and went to swap it last night. I had a heck of a time pulling the upper hose (which runs to the intake, when the valve cycles open) off the old purge valve. Once I did, I saw it was crusted with white powder around the inside where it connected to the old valve. And when I tipped the valve down, white powder/crud sprinkled out of the corresponding port!

Monitoring the fuel tank sensor/tank pressure this afternoon (with full tank) shows a lot less jumping around. Not sure whether that's b/c of the full tank or the new(er) valve, or both. My working theory, however, is that during the time (couple thousand miles) that the evap hose connecting the rear and front charcoal canisters was chewed open by mice, the purge valve, when duty cycled on by PCM, would suck air through that large hole. If it was raining or even damp out, that introduced water into the purge valve, and likely crudded it up, compromising performance.

Anyway, I thought I'd report this in case this had something to do with my gas tank filling problem. If the old purge valve was working only partially, it might not have fully evacuated the canisters of gas vapor or removing pressure from the tank. This might have left canisters more likely to block air flow out of the top of the tank --causing gas fill problems.
 






Drewmcg

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Shoot. After several fill-ups, the problem with the pump continually shutting off is as bad as ever. And I can smell stinky fuel vapors every now and then (probably not a good thing).

Found a new Motorcraft CX-1689 canister for $70 shipped. Now we'll see how fun that sucker is going to be to put in. I figure I'll replace rear one first and see what that does. Wish me luck.
 






Donystoy

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I had the same issue with my 02 last year. Found online that these filler pipes are notorious for rusting inside and plugging the screen on the end. I had taken the vehicle to my mechanic (I will not work on fuel tanks or related components due to safety concerns) who decided to replace the valve assembly on the tank. This did not repair the issue. I picked up a filler assembly that for some reason he was not able to source and had him install it. This fixed the problem.
 






Drewmcg

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I think you're referring to the filler neck, right? https://www.rockauto.com/en/moreinfo.php?pk=4840941&cc=1377660&jsn=321
This part does not show a separate vent hose (see my photos above, with hanger sticking out), which actually does not attach to the filler neck, but instead to the side of the gas cap housing.

The photo linked to above does show a second, much smaller diameter metal tube. Frankly, I don't know what that tube is for. Is that the tube that rusted up in your case? I'm not sure how that tube could cause back pressure, but maybe. Thanks.
 






Donystoy

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Yes that is the assembly that I replaced. There is a screen at the bottom end that gets plugged with corrosion. If the fuel cannot go through it to get to the tank it causes back pressure that triggers the pump nozzle to shut off. I guess you could remove it and try to clean it out but from what I saw happens to these with corrosion I opted to just install a new one. Got mine from Carquest. Part #GST FN840. I paid $250 Canadian for the part.
 






Drewmcg

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Yes that is the assembly that I replaced. There is a screen at the bottom end that gets plugged with corrosion. If the fuel cannot go through it to get to the tank it causes back pressure that triggers the pump nozzle to shut off. I guess you could remove it and try to clean it out but from what I saw happens to these with corrosion I opted to just install a new one. Got mine from Carquest. Part #GST FN840. I paid $250 Canadian for the part.
Wow, great information. Thank you! I've been chasing this issue for weeks w/o finding this info. I'm inclined to just ram a length of vinyl hose slighty smaller in diameter than the gas pump handle flapper down through the filler neck to poke a hole in that screen. If that solves the problem I could either live with it (cheap solution) or replace the entire filler neck. Either way I could return the canister and save a lot of frustration. If it does not fix the problem, then one more confirmation that I need a new canister after all. Thanks, again.
 






rrgone

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I have several pages saved from the 2003 Explorer service manual for the fueling hoses and emissions stuff. Used to have the full manual until a hard drive died. Anyway, if you haven't seen the FSM pages let me know and I can email to you. Send a PM with email address if interested.
 






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