Weird gas pumping issue

[Bsb120]

ah it's not that bad, drop the spare, the tubes to the canister and valve are quick disconnect, take off the old ones, put on the new ones, it helps if you disconnect the filler tube from the body and pull it down from the inside to hook up the new filter & tube, then shove the filler tube back up and re-attach it. the one under the hood on the intake only takes a couple minutes super easy. if you are reasonably talented it shouldn't take more than 30-45 minutes from start to finish.
helps if you watch a couple youtube vidoe's so you know what to expect.

Yeah the reasonably talented part ain’t the problem. I did intake manifold gaskets and valve cover gaskets back when I had my 2002. But anyways I was crawling around under it and the part that goes up towards the filler neck is just hanging under truck. Where exactly is it supposed to be? Could that be causing the problem? And would that be reason to assume that component has been replaced?

 

[Bsb120]

also does the gas cap look like an original gm gas cap or an aftermarket one? not directly suggesting its your problem but if your going to shotgun it and its not original. only a month of ownership just makes me wonder if it may have popped up once or twice for the previous owner. if they put an aftermarket gas cap on there it might be adding to the real problem. the aftermarket ones tend to be 50 50.

Since you ask, I have never actually took the time to see what the factory gas caps look like. The one that’s on it has the little plastic string to keep you from losing it. And it’s bright yellow

 

[drakon543]

probably original then just wanted to mention it since its a common go to for evap codes

 

[Doubeleive]

Yeah the reasonably talented part ain’t the problem. I did intake manifold gaskets and valve cover gaskets back when I had my 2002. But anyways I was crawling around under it and the part that goes up towards the filler neck is just hanging under truck. Where exactly is it supposed to be? Could that be causing the problem? And would that be reason to assume that component has been replaced?

the little box filter at the end of the flex tube clips and zip ties to the side of the top of the filler tube, this just keeps it held up in a space where it won't get water or mud/dirt in it, just placing it up there now is probably not going to fix the issue.

 

[89Suburban]

I just went through this with my evap valve. I didn’t have a filling issue though. But you definitely could smell heavy fuel fumes when the cap was off to fill.

 

[OR VietVet]

If I recall, besides just age, the main reason that these evap systems fail is from over filling the fuel. If the gas filler nozzle clicks off, just round to the nearest dollar ($) and let it go. Too much fuel and it backs up in to the evap system and it all starts from there. At least it used to when I was in shops. If there is a design change I am unaware of it.

 

[HiHoeSilver]

If I recall, besides just age, the main reason that these evap systems fail is from over filling the fuel. If the gas filler nozzle clicks off, just round to the nearest dollar ($) and let it go. Too much fuel and it backs up in to the evap system and it all starts from there. At least it used to when I was in shops. If there is a design change I am unaware of it.

This is definitely a contributor. I don't ever round off. It's a credit card, who cares? Clicks off, I'm done.

 

[donjetman]

I'm with Nate, I don't round off either. Off is off.

 

[Bsb120]

Well mines been doing this since I got it I guess? I thought maybe it would fix it self. If coarse I went to test drive it and no codes, no issues, but the day I picked it up and drove it around all day that evening I got the p0455. I haven’t changed any of those parts yet. I been trying to track down. Front end rattle. But that’s irrelevant to this thread. So I guess when I get enough money saved up I’ll just get all three of the usual suspects and swap them out.

 

[KATfishing]

I changed the purge valve, gas cap and vent valve assembly (in that order) when this happened. I did not change the canister. In my research, I had read the canister is usually not the issue and shouldn't be too quickly condemned, and in my case 3 years later, all is still good with original canister still in place. The vent valve assembly is an updated part, and resolved my issues with symptoms as you describe. https://www.amazon.com/gp/product/B00RW3A04E/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 Also, you will need this jumper harness: https://www.amazon.com/gp/product/B0055B121U/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Check YouTube... it's pretty easy changeout once you understand how the clips release. You will need to lower the spare tire and slide it out of the way. Also, definitely wear a mask and safety glasses for all the debris that will drop down on you. It's a messy job, but a creeper and basic hand tools are all that's needed, along with some zip ties to connect the hose to the filler tube. All of my evap trouble codes and symptoms went away with the vent valve change.