[Hi-Country]

Stopped for gas...after a few seconds the gas nozzle shuts off...like it would normally do when topping off. No matter what position the nozzle was in I got the same refusal.

Now, I can't remember this ever happening in the past. 3/4 tank dash gauge, so rule out any back pressure.

I stopped at another station...same results, although at this pump I was able to feather the nozzle manually and slowly feed fuel. Not the norm by any means.

Anyone else experienced this...2017.

 

[davester3500]

why can't it be back pressure? The air in the tank has to go somewhere.

My '12 also has this problem, when I filled it for the first time (it's new to me), I had to dribble the fuel in. I have to examine/test the evap system to check that it does vent through the canister when pressure builds up in the tank.

If yours suddenly stopped filling right, I would perhaps start with looking at the evap venting solenoid (probably not the right term), that vents air through the canister, then out to air.

 

[Walkers]

Most likely the solenoid valve off the charcoal canister has failed shut. Other option is a kinked vent hose or the charcoal canister is plugged up.

 

[Hi-Country]

Well, it sounds like I have some troubleshooting to do. I appreciate the leads fellows.

YouTube to the rescue🤞 1st video showed cannister failure where the carbon pellets broke free and fouled the lines.

I might add that I have NO check engine light iluminated on the dash at present...could that be forthcoming as the venting problem continues to get worse?

I don't own a reader to decifer OBD2-Codes.

Need to investigate whether or not GM has a TSB covering this model year.

Hate to be at the mercy of the dealer, but I just don't want to be changing parts for the sake of changing parts.

 

[Hi-Country]

why can't it be back pressure? The air in the tank has to go somewhere.

My '12 also has this problem, when I filled it for the first time (it's new to me), I had to dribble the fuel in. I have to examine/test the evap system to check that it does vent through the canister when pressure builds up in the tank.

If yours suddenly stopped filling right, I would perhaps start with looking at the evap venting solenoid (probably not the right term), that vents air through the canister, then out to air.

Did you end up replacing the cannister or solenoid or both?

 

[Stolisan]

Same thing happened to my truck. I always thought it was the gas station nozzle because it didn't happen all the time. No CEL until the day I took it for a smog inspection. It took a while to diagnose but ended up being a plugged charcoal canister. And don't try to flush it with water like the YT video.

 

[davester3500]

Did you end up replacing the cannister or solenoid or both?

I haven't figured out the problem. I've removed the cannister, banged it around a bit to loosen the contents, then blew through it, to make sure air flows through the 3 ports. Now I'm working on testing the vent solenoid, to check if air flows through the line when it's commanded open.

 

[Hi-Country]

I haven't figured out the problem. I've removed the cannister, banged it around a bit to loosen the contents, then blew through it, to make sure air flows through the 3 ports. Now I'm working on testing the vent solenoid, to check if air flows through the line when it's commanded open.

Is this on your '04?

 

[Hi-Country]

Same thing happened to my truck. I always thought it was the gas station nozzle because it didn't happen all the time. No CEL until the day I took it for a smog inspection. It took a while to diagnose but ended up being a plugged charcoal canister. And don't try to flush it with water like the YT video.

Did you replace it or dealer?

 

[davester3500]

No, I've got a '12 Silverado 3500 that I'm working on. I tested the vent solenoid, and it opens/closes on command and passes/blocks airflow today, and tested that the gas tank pressure sensor is registering, so tomorrow the truck should be mobile finally, and I'll see how filling it up goes.

 

[Hi-Country]

No, I've got a '12 Silverado 3500 that I'm working on. I tested the vent solenoid, and it opens/closes on command and passes/blocks airflow today, and tested that the gas tank pressure sensor is registering, so tomorrow the truck should be mobile finally, and I'll see how filling it up goes.

Very well...so if I may...by what means did you give a command to cycle the solenoid? And the sensor? Thanks for your time.

 

[Stolisan]

Did you replace it or dealer?

I did replaced it. I used a Dorman part. The hardest part was trying to figure out how to remove the hoses. It has special clips and tabs that look easy to break.

I took apart the old one to see what was wrong and the pellets broke down causing the restriction. I emptied the pellets into a bucket and rinsed them until the black water turned clear. Then I dried them and poured them back into the canister. It surprised me how little I lost. I'd say maybe 5%, no more than 10%. There's a breathable pad and spring to keep everything tight so the pellets aren't constantly bouncing around. By blowing through I could really tell the difference. If I knew It could be rebuilt, I would've tried that first but I needed to get the smog inspection. I'm not suggesting anyone try to rebuild it. I had to use a hack saw to cut the top off.

I tested the vent valve and purge solenoid by removing them and supplying 12 volts and blowing through them. IIRC the vent is normally open, the purge is normally closed.

 

[Hi-Country]

I did replaced it. I used a Dorman part. The hardest part was trying to figure out how to remove the hoses. It has special clips and tabs that look easy to break.

I took apart the old one to see what was wrong and the pellets broke down causing the restriction. I emptied the pellets into a bucket and rinsed them until the black water turned clear. Then I dried them and poured them back into the canister. It surprised me how little I lost. I'd say maybe 5%, no more than 10%. There's a breathable pad and spring to keep everything tight so the pellets aren't constantly bouncing around. By blowing through I could really tell the difference. If I knew It could be rebuilt, I would've tried that first but I needed to get the smog inspection. I'm not suggesting anyone try to rebuild it. I had to use a hack saw to cut the top off.

I tested the vent valve and purge solenoid by removing them and supplying 12 volts and blowing through them. IIRC the vent is normally open, the purge is normally closed.

You didn't mention any codes that might have showed up. Were you able to extract the codes associated with Evap trouble?

 

[Stolisan]

You didn't mention any codes that might have showed up. Were you able to extract the codes associated with Evap trouble?

When I was having trouble pumping gas for a few years and there were no codes. On the day I was going for the smog inspection, the light came on. I don't remember the code but the description was evap system. When I looked it up, one of the symptoms were difficulties pumping gas. That's when I figured out it wasn't the gas station's faulty nozzles, it was the charcoal canister.

I narrowed it down to either the canister or vent valve. If it were a leak or the pressure sensor, it would show a different code. It couldn't be the purge solenoid because it's closed when the truck is off. If it failed open, the tank pressure would vent to the intake manifold and I wouldn't have trouble filling the tank.

The GMT800s had a problem with the vent valve getting plugged with mud because of the location under the truck. On the newer trucks, they added a hose to move the vent where it's more protected. You might want to check that it's not clogged.

At 4:33 YT it shows the hose coming from the vent valve attached to the filler neck and just above the yellow rag, in the box looking thing is where it vents to. It probably has a piece of foam in it. Here's what it looks like when it fall off. vent hanging

 

[Hi-Country]

You mentioned you hacksawed off the top of the canister...did I read that correctly.

There is a vent valve out there that eliminates the long hose that trails to the rear of the truck. It's just a stub section of hose (clamps) and housing w/foam filter...easy access for routine cleaning👍

 

[buckwild27]

My 2013 has this issue when it's really cold outside. I usually rotate the gas nozzle as far sideways as I can get it and still be in the tank. Start pumping and after about 30 seconds slowly rotate it down and in. It says running after that. No lights or codes ever come up been this was for years.

 

[Hi-Country]

That's an interesting take on what seems to prevalent with these trucks. Damn over engineered emissions...that all started years ago with a smog pump and an EGR valve. Both wreaked havoc ever since.

 

[buckwild27]

That's an interesting take on what seems to prevalent with these trucks. Damn over engineered emissions...that all started years ago with a smog pump and an EGR valve. Both wreaked havoc ever since.

Agreed

 

[davester3500]

Very well...so if I may...by what means did you give a command to cycle the solenoid? And the sensor? Thanks for your time.

I have a tech2win setup (basically the dealer-computer) for doing it.

 

[Hi-Country]

I have a tech2win setup (basically the dealer-computer) for doing it.

Pays to have the right tools...nice!

To bad the likes of Auto-Zone and or O'Reily's doesn't offer such a diagnostic tool as a loaner....as they do other specialty tools.