2008 Yukon gas tank issue.

[olliec420]

A lot of good info here. I too am having intermittent issues with filling tank and rough idle. No codes. Sometimes feels like its a bit down on power and idles rougher than I'd like. Some times it feels great and fills fine! Watched the videos posted here. I have no plans on getting another car and just rebuilt the trans in this thing. Trying to get it dialed in. Whats to say I just replace the canister and solenoids? Theyre not too expensive. (to be honest I kinda like shooting the parts cannon at it, Ive replaced a lot so far) Oh and Im guilty of overfilling, just learned that was bad here.

 

[Fless]

If you're going to replace all those things, then while it's apart take a little time to blow some air through the lines. Not a lot of pressure, just enough to be sure the lines are clear.

 

[Sam Harris]

If you're going to replace all those things, then while it's apart take a little time to blow some air through the lines. Not a lot of pressure, just enough to be sure the lines are clear.

Agree. Or you can replace the lines as well.. but they’re a little spendy.

 

[olliec420]

Agree. Or you can replace the lines as well.. but they’re a little spendy.

You talking about the lines included with the Vent Valve Assembly or different lines?

More Information for GM GENUINE 23481275

More Information for GM GENUINE 215464

These are the two things I was planning to order.

 

[Sam Harris]

I think that’s it. Never done that job myself, but when I looked up all the parts a while back they were pretty expensive.

 

[olliec420]

Simplify it like this: The tank needs to vent, and it vents into the charcoal ("EVAP") canister. The EVAP canister vents into the engine. Find out why the tank isn't venting. A quick test is to disconnect the largest hose on the canister. I think it's the center one. If you can fill up with no problems, then the canister is clogged. If the problem persists, the issue is before the canister, so in that hose or the tank itself.

So I did the disconnect and tried to fill up. I am still unable to fill. The filler tube fills up and then the gas pump shuts off. I can head the gas running down in the tank and air coming from the breather tube that vents in to the filler tube. Obviously not supplying enough air to make up for the fluid coming in. Whats the bad news? I just rebuilt the trans on this thing and have replaced a lot of parts in the last year. Im starting to get a lil annoyed. I wouldn't mind just throwing on a new canister and valve but this makes me think its a problem in the tank.

 

[theo robertson]

I had the same problem. I changed the canister and the valve problem solved.

 

[Geotrash]

So I did the disconnect and tried to fill up. I am still unable to fill. The filler tube fills up and then the gas pump shuts off. I can head the gas running down in the tank and air coming from the breather tube that vents in to the filler tube. Obviously not supplying enough air to make up for the fluid coming in. Whats the bad news? I just rebuilt the trans on this thing and have replaced a lot of parts in the last year. Im starting to get a lil annoyed. I wouldn't mind just throwing on a new canister and valve but this makes me think its a problem in the tank.

It's possible for the pellets to make their way into the lines in the tank and create a blockage. Some folks have had to drop their tank to get the lines fully cleaned out.

 

[Fless]

So I did the disconnect and tried to fill up. I am still unable to fill. The filler tube fills up and then the gas pump shuts off. I can head the gas running down in the tank and air coming from the breather tube that vents in to the filler tube. Obviously not supplying enough air to make up for the fluid coming in. Whats the bad news? I just rebuilt the trans on this thing and have replaced a lot of parts in the last year. Im starting to get a lil annoyed. I wouldn't mind just throwing on a new canister and valve but this makes me think its a problem in the tank.

I would clarify that the canister vents to the engine only when a purge event is taking place. And that's the "fume" or dirty side of the canister. The clean side vents through the vent valve (when open).

The tank fumes vent to the canister, and it in turn vents cleaned air while filling the tank, so long as the key is in the engine off position.

You likely have a partially blocked line from the tank to the canister, or the canister is blocked. If I understand it correctly, you already disconnected the line from the tank that connects to the canister, so suspect that line.

 

[Geotrash]

I would clarify that the canister vents to the engine only when a purge event is taking place. And that's the "fume" or dirty side of the canister. The clean side vents through the vent valve (when open).

The tank fumes vent to the canister, and it in turn vents cleaned air while filling the tank, so long as the key is in the engine off position.

You likely have a partially blocked line from the tank to the canister, or the canister is blocked. If I understand it correctly, you already disconnected the line from the tank that connects to the canister, so suspect that line.

All true. My hypothesis is that the pellets end up in the vent line in the tank through gravity because the canister sits higher than the top of the tank. And when they get in there, they bind together to create a plug in the vent line.

 

[olliec420]

Ok so I have had my vent line disconnected from the canister for about 2 weeks. I haven't been driving that much but a couple times I went out and the DIC said "Tighten Gas Cap". Yesterday it wouldn't remote start and I turned it on and the check engine light was on for Evap system small leak. That means "some" air is getting out of the vent.

I just blew some air in to the tank with a rag and when released I can hear the tank holding pressure. Is there any danger in putting more air pressure in the tank with the vent line disconnected as to help blockage move out? Also, do we think that the purge to engine line from the canister is clogged too?

I got the new canister but I don't want to install it yet until problem is fixed of course. And next Sunday (week from today) Im going on a 1000 mile round trip and will be gassing up a bunch. I can get by slowly if need be but would like to fix it before then without having to drop the tank. Its about 1/2 full right now. Those who have dropped tank, how bad is it?

 

[Sam Harris]

Ok so I have had my vent line disconnected from the canister for about 2 weeks. I haven't been driving that much but a couple times I went out and the DIC said "Tighten Gas Cap". Yesterday it wouldn't remote start and I turned it on and the check engine light was on for Evap system small leak. That means "some" air is getting out of the vent.

I just blew some air in to the tank with a rag and when released I can hear the tank holding pressure. Is there any danger in putting more air pressure in the tank with the vent line disconnected as to help blockage move out? Also, do we think that the purge to engine line from the canister is clogged too?

I got the new canister but I don't want to install it yet until problem is fixed of course. And next Sunday (week from today) Im going on a 1000 mile round trip and will be gassing up a bunch. I can get by slowly if need be but would like to fix it before then without having to drop the tank. Its about 1/2 full right now. Those who have dropped tank, how bad is it?

If there are charcoal pellets in the lines, I wouldn’t try blowing them through with it attached. I think the best option is to pull the lines off, and see if you can get the crud out that way.

 

[olliec420]

Ok fixed, it will take gas now. In an attempt to try fix methods from easy to hard... I put it on the lift, as I mentioned before the vent line was disconnected from the canister. I opened the fill and put a shop vac suction on the vent line. Took the vac on and off quickly and tons of charcoal pellets came out. Then put the shop vac in reverse on the fill and wind was blowing out the vent. I disconnected the rest of the lines from the canister, removed canister and installed the new one, reconnected the lines, went to gas station and its taking gas! I didn't know what I was doing or if it was gonna work or I would have made a video on it. Much easier than all the other videos I saw, but also it may not fix everyone's problem. Needless to say, no more topping off the tank for me.

 

[Sam Harris]

Ok fixed, it will take gas now. In an attempt to try fix methods from easy to hard... I put it on the lift, as I mentioned before the vent line was disconnected from the canister. I opened the fill and put a shop vac suction on the vent line. Took the vac on and off quickly and tons of charcoal pellets came out. Then put the shop vac in reverse on the fill and wind was blowing out the vent. I disconnected the rest of the lines from the canister, removed canister and installed the new one, reconnected the lines, went to gas station and its taking gas! I didn't know what I was doing or if it was gonna work or I would have made a video on it. Much easier than all the other videos I saw, but also it may not fix everyone's problem. Needless to say, no more topping off the tank for me.

I’m happy that worked for you! Hope you got all of them out.

 

[testdepth]

All true. My hypothesis is that the pellets end up in the vent line in the tank through gravity because the canister sits higher than the top of the tank. And when they get in there, they bind together to create a plug in the vent line.

View attachment 397192

I have a 2012 Denali that started having the problem of fuel pump clicking off every few seconds. I replaced the EVAP canister and the solenoid valve. When I disconnected the vapor line going between the tank and canister I saw carbon pellets fall out of the line. I used a vacuum to try and suck them out. Put it all back together and no change the pump still shuts off. I assume there is carbon in the line clogging it. Can the line be cleared without dropping the tank?

 

[testdepth]

Ok so I have had my vent line disconnected from the canister for about 2 weeks. I haven't been driving that much but a couple times I went out and the DIC said "Tighten Gas Cap". Yesterday it wouldn't remote start and I turned it on and the check engine light was on for Evap system small leak. That means "some" air is getting out of the vent.

I just blew some air in to the tank with a rag and when released I can hear the tank holding pressure. Is there any danger in putting more air pressure in the tank with the vent line disconnected as to help blockage move out? Also, do we think that the purge to engine line from the canister is clogged too?

I got the new canister but I don't want to install it yet until problem is fixed of course. And next Sunday (week from today) Im going on a 1000 mile round trip and will be gassing up a bunch. I can get by slowly if need be but would like to fix it before then without having to drop the tank. Its about 1/2 full right now. Those who have dropped tank, how bad is it?

I tried this using my leaf blower and some PVC fittings reduced down to fit the filler hole tight. I dropped the spare tire and disconnected the vent line from the EVAP canister. I blew out the line and several charcoal pellets came out. I connected everything back up and went to the gas station. I tried Circle K pump and a different Petrol pump. Both pumps continue shutting off as before. I can hear the filler neck filling up and then the pump kicks off. Maybe I did not get all the pellets out of the vent line so I will try it again when the engine cools off. I HATE GMC!

 

[testdepth]

Before I blew out the vapor line going to the EVAP canister from the fuel pump: When I disconnected the line from the EVAP canister gas dripped out of the canister. This might be normal? The EVAP canister and Solenoid are brand new.

 

[Sam Harris]

Before I blew out the vapor line going to the EVAP canister from the fuel pump: When I disconnected the line from the EVAP canister gas dripped out of the canister. This might be normal? The EVAP canister and Solenoid are brand new.

There should definitely not be any fuel in the Evap canister.

 

[Fless]

There should never be gas in the canister. That's an indication that the tank has been overfilled and the excess fuel is making its way through the evap lines into the canister. When fueling, stop when the pump clicks off the first time.

 

[testdepth]

There should never be gas in the canister. That's an indication that the tank has been overfilled and the excess fuel is making its way through the evap lines into the canister. When fueling, stop when the pump clicks off the first time.

Not sure whats going on then. The tank is only half full.