2008 LT 3.9L Evap charcoal canister
jwichman
11-21-2020, 08:27 AM
No drivability issues other than an occasional P0446 code however almost impossible to refuel. I checked the evap vent valve found completely plugged with gravel road dust, cleaned it out and replaced. Still have refuel problem.
Planning a charcoal canister replacement. Can’t seem to find much info on the replacement, how big of a job is it and Does the fuel tank have to be dropped completely or just lowered slightly? Any other parts that should be replaced while I’m there i.e. tank strap bolts or nuts?
Thanks
Planning a charcoal canister replacement. Can’t seem to find much info on the replacement, how big of a job is it and Does the fuel tank have to be dropped completely or just lowered slightly? Any other parts that should be replaced while I’m there i.e. tank strap bolts or nuts?
Thanks
j cAT
02-09-2021, 11:47 AM
If you fill the gas tank to the max then the charcoal canister will get liquid fuel in it and then the canister will get damaged.
jwichman
10-16-2021, 04:40 PM
Finally got around to replacing the EVAP charcoal canister, removed both ends and blew out all of the hoses, including the vent valve hose, the purge valve hose, the fuel fill neck hose and the hose between the charcoal canister and fuel tank. Put it all back together and I’m still unable to pump gas into the tank at much more than a trickle (22mins to pump 10gals of gas). The vent valve is also relatively new and verified to be open. The EVAP system appears to be operating correctly as I’m able to monitor EVAP demand and fuel tank pressure via DIY grade scan tool.
What am I missing. It seems like there has to be a restriction in the fuel fill hose that allowed compressed air to pass but is not allowing fuel to pass. Anyone have any ideas??
Thanks in advance for anything offered.
What am I missing. It seems like there has to be a restriction in the fuel fill hose that allowed compressed air to pass but is not allowing fuel to pass. Anyone have any ideas??
Thanks in advance for anything offered.
Blue Bowtie
10-16-2021, 09:20 PM
Your supposition may be correct. I've had a few GM trucks which had an anti-surge and anti-siphon tube within the filler neck and tank connection hose. Some of those can get distorted or damaged so that normal fuel flow is impossible. The mid-2000s Impalas use a relatively small fill tube with a separate vent line. the EVAP should not affect fuel filling whatsoever, since the tank vent is piped directly back to the fill line flange. Id you live in an area with those "vapor recovery" fuel hose nozzles at the pump, good luck.
jwichman
10-17-2021, 09:04 AM
Your supposition may be correct. I've had a few GM trucks which had an anti-surge and anti-siphon tube within the filler neck and tank connection hose. Some of those can get distorted or damaged so that normal fuel flow is impossible. The mid-2000s Impalas use a relatively small fill tube with a separate vent line. the EVAP should not affect fuel filling whatsoever, since the tank vent is piped directly back to the fill line flange. Id you live in an area with those "vapor recovery" fuel hose nozzles at the pump, good luck.
Thanks for the response. I was getting a EVAP vent code 446 and the charcoal canister as well as the EVAP vent valve were full of gravel road dust so my efforts were not wasted. I wish I’d had notice the vent line on the fuel fill neck while I was under there cleaning stuff out. I now agree the EVAP vent should not affect fuel fill.
Thanks for the response. I was getting a EVAP vent code 446 and the charcoal canister as well as the EVAP vent valve were full of gravel road dust so my efforts were not wasted. I wish I’d had notice the vent line on the fuel fill neck while I was under there cleaning stuff out. I now agree the EVAP vent should not affect fuel fill.
Blue Bowtie
10-17-2021, 12:16 PM
If the filler tube is not distorted, collapsed, or bent, and the ~ 3/8" vent line running alongside it is intact, there probably isn't much more to be done. The filler neck assembly could be removed and inspected for obstructions, but be sure the fuel level in the tank is low enough to permit that without creating a massive leak.
jwichman
10-29-2021, 09:18 PM
Pulled the fill neck pipe from the gas cap to the fuel tank completely out. I confirmed there is a roll over valve inside the fuel tank, mine was not stuck. There is a anti siphon screen that is inside the filler neck pipe, I confirm mine was not plugged. Confirmed that the small vent pipe along side of the filler neck was not plugged. I had to remove the Evap vent valve and associated hose in order to remove the filler neck piping. I gave the EVAP vent valve piping one more look before putting it back in place and found that it was plugged with gravel road dust. Blew it out (there was a surprising amount in there) with compressed air, reassembled everything and problem solved. Filled the tank 13gals in less than 5 mins, pump never kicked off, there wasn’t even a gurgle. I have to take back my statement, the EVAP vent valve does vent the fuel tank during refueling.
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