- Jul 22, 2015
- 2,724
I'll start by saying there are members here that discounted the effectiveness of doing this, but I'm here to report that it worked for me, and it's worth a try, IMO.
Before I did this, I had to fill the tank very, very slowly. Like '30 minutes' slowly, for a 26gal tank. And backing off the nozzle from the end of the filler neck did NOT help. It was bad enough that I'd never really fill the tank, but put in $20 worth, half a tank, that sort of thing. On a long trip, this is a real killer (not to mention annoying to people waiting in line behind you to fill their own tanks.)
After searching on Google, I came across a couple of YT vids that described this as helping. So I followed the given procedure. You don't have to relieve fuel pressure, etc. - this affects only the evap system. (there is a small chance that some fuel might come out, if your canister is *really* clogged -- but it won't be pressurized -- and if this happens, your canister is hosed, due to the fuel -- so just skip to 'remove and replace'.)
First... if you have active or pending codes concerning the evap system (small / large leak, purge valve, etc.) -- take care of those first, before doing the procedures below. Mine had no codes at all, so I was losing nothing but some time by trying this.
- Remove the canister (on the GMT800s, it's just behind the fuel tank. There are three different types of connectors, one for each line (thanks, GM). Bringing a pick tool can be helpful for one of the connectors; the other two are pretty much 'squeeze / release'.
You'll likely smell fuel vapors, but no raw fuel will (should) be discharged... didn't happen with me. One 13mm bolt holds the retaining bracket in place. I removed it and lowered the canister before disconnecting the most difficult connector, but in retrospect, it would've been easier to disconnect all three *before* removing the bracket / canister.
Here's a stock image (from a YT vid); this is from a Silvy / Sierra, but I believe the canister for the 360 series is similar:
(note above, that the orifice the author is pointing to is the one you DON'T want to put air through!)
Mine had text labels molded into the plastic signifying what each was for, but I can't find a pic (or description) of those labels as I write this. It appears that the manufacturer may have stopped molding the labels onto the canister at some point. Since all three ports are different sizes, I'll guess that GM figured out that no one could possibly goof up connecting the ports and gave the OK to make unlabeled canisters at some point (especially if they could save a penny or two per unit).
(after looking on my phone, sorry... no pics. IIRC, the larger one of the two on the right is labeled 'air' or 'fresh' or 'fresh air'. That's where the compressed air goes)
- Once disconnected, shake the canister a few times. You should hear at least some of the media (activated charcoal?) rattling inside. If not... you may wind up replacing your canister sooner, rather than later. Mine was like this, and I'll probably get a new canister. But it *did* improve things (more on this below), even though I really didn't hear the media loosened up inside after I blew air through it.
- Give the opposite end of the canister (with no openings) a few raps on a solid surface. If you see dust coming out when you do this, there's a good chance you'll free up a lot of airflow. Especially if you drive on unpaved / gravel roads.
-Get some compressed air (even the cans with the triggers can work -- it's what I used, rather than turning on my compressor). Feed it through the large orifice on the right, as shown in the pic above. You're not supposed to 'backflush' it through the smaller hole (normal air flow is from larger -> smaller). Give the canister a few more raps, and repeat this a few times. You should eventually feel air coming out of the smaller hole. I didn't - at first. Mine was really clogged, and *nothing* came out of the ports at all. No dirt, no air.
In my case, I *did* reverse the air flow (putting it into the smaller orifice), and after going back and forth, I finally felt air coming out of the opposite orifice. Not an equal amount to what I put in, but at least I got some flow out of it. After a few minutes, I decided it was as good as I was going to get it and reinstalled the canister.
Fast forward a few days, and...
Today I went and got gas. Moment of truth...
To my small delight, I was able to put the pump on the 'slowest' notch and fill the tank. Well, almost. It did click off twice... but I was able to get fully 3/4 of a tank in before I had to start filling very slowly by hand again. Since I normally fill at the 'slow' notch / speed in all of my vehicles, color me happy. And, I have no codes, either after performing the procedure or filling the tank. I figure it took me 10-12min (estimated) to fill, total, and half of that was getting the last 1/4 of a tank in, as well as going inside to get a receipt, since none printed at the pump.
As I mentioned above -- I know I'll likely have to replace the canister, but at least I can put a full tank of gas in the truck now. And as I alluded to at the beginning... after having the truck for a full year, this was the first time I actually *filled* the tank. If you're having trouble filling your tank, like I was... it's definitely worth a try. Really made my day to have success with this.
Before I did this, I had to fill the tank very, very slowly. Like '30 minutes' slowly, for a 26gal tank. And backing off the nozzle from the end of the filler neck did NOT help. It was bad enough that I'd never really fill the tank, but put in $20 worth, half a tank, that sort of thing. On a long trip, this is a real killer (not to mention annoying to people waiting in line behind you to fill their own tanks.)
After searching on Google, I came across a couple of YT vids that described this as helping. So I followed the given procedure. You don't have to relieve fuel pressure, etc. - this affects only the evap system. (there is a small chance that some fuel might come out, if your canister is *really* clogged -- but it won't be pressurized -- and if this happens, your canister is hosed, due to the fuel -- so just skip to 'remove and replace'.)
First... if you have active or pending codes concerning the evap system (small / large leak, purge valve, etc.) -- take care of those first, before doing the procedures below. Mine had no codes at all, so I was losing nothing but some time by trying this.
- Remove the canister (on the GMT800s, it's just behind the fuel tank. There are three different types of connectors, one for each line (thanks, GM). Bringing a pick tool can be helpful for one of the connectors; the other two are pretty much 'squeeze / release'.
You'll likely smell fuel vapors, but no raw fuel will (should) be discharged... didn't happen with me. One 13mm bolt holds the retaining bracket in place. I removed it and lowered the canister before disconnecting the most difficult connector, but in retrospect, it would've been easier to disconnect all three *before* removing the bracket / canister.
Here's a stock image (from a YT vid); this is from a Silvy / Sierra, but I believe the canister for the 360 series is similar:
(note above, that the orifice the author is pointing to is the one you DON'T want to put air through!)
Mine had text labels molded into the plastic signifying what each was for, but I can't find a pic (or description) of those labels as I write this. It appears that the manufacturer may have stopped molding the labels onto the canister at some point. Since all three ports are different sizes, I'll guess that GM figured out that no one could possibly goof up connecting the ports and gave the OK to make unlabeled canisters at some point (especially if they could save a penny or two per unit).
(after looking on my phone, sorry... no pics. IIRC, the larger one of the two on the right is labeled 'air' or 'fresh' or 'fresh air'. That's where the compressed air goes)
- Once disconnected, shake the canister a few times. You should hear at least some of the media (activated charcoal?) rattling inside. If not... you may wind up replacing your canister sooner, rather than later. Mine was like this, and I'll probably get a new canister. But it *did* improve things (more on this below), even though I really didn't hear the media loosened up inside after I blew air through it.
- Give the opposite end of the canister (with no openings) a few raps on a solid surface. If you see dust coming out when you do this, there's a good chance you'll free up a lot of airflow. Especially if you drive on unpaved / gravel roads.
-Get some compressed air (even the cans with the triggers can work -- it's what I used, rather than turning on my compressor). Feed it through the large orifice on the right, as shown in the pic above. You're not supposed to 'backflush' it through the smaller hole (normal air flow is from larger -> smaller). Give the canister a few more raps, and repeat this a few times. You should eventually feel air coming out of the smaller hole. I didn't - at first. Mine was really clogged, and *nothing* came out of the ports at all. No dirt, no air.
In my case, I *did* reverse the air flow (putting it into the smaller orifice), and after going back and forth, I finally felt air coming out of the opposite orifice. Not an equal amount to what I put in, but at least I got some flow out of it. After a few minutes, I decided it was as good as I was going to get it and reinstalled the canister.
Fast forward a few days, and...
Today I went and got gas. Moment of truth...
To my small delight, I was able to put the pump on the 'slowest' notch and fill the tank. Well, almost. It did click off twice... but I was able to get fully 3/4 of a tank in before I had to start filling very slowly by hand again. Since I normally fill at the 'slow' notch / speed in all of my vehicles, color me happy. And, I have no codes, either after performing the procedure or filling the tank. I figure it took me 10-12min (estimated) to fill, total, and half of that was getting the last 1/4 of a tank in, as well as going inside to get a receipt, since none printed at the pump.
As I mentioned above -- I know I'll likely have to replace the canister, but at least I can put a full tank of gas in the truck now. And as I alluded to at the beginning... after having the truck for a full year, this was the first time I actually *filled* the tank. If you're having trouble filling your tank, like I was... it's definitely worth a try. Really made my day to have success with this.
