Fuel backing up in filler neck at pump

[RocketcCutlass]

2011 Tahoe LT. So I did the research on here and determined it seems like the tank purge solenoid is bad. I’ve seen several threads that were a little confusing to me. To verify, we don’t have a metal flapper valve in the filler neck right? I honestly never paid attention to that and my thought was it may have broken off and is blocking the filler neck, if we have one. Also if I do have to replace the purge solenoids and charcoal canister what are the GM part numbers I need? LMG 5.3 if it matters. I’ve seen a few different numbers and I’m just wanting to avoid buying the wrong parts and taking the car off the road. I’m limited on time and $$.

 

[strutaeng]

Shouldn't it be the vent solenoid that's bad? The purge only opens when the ECU commands the gases in the charcoal canister be sent to the intake for consumption under certain conditions. You can unplug the purge solenoid at the vapor hose and see what it does.

But I did have an issue with my OBS K3500 when I just bought it. The fuel pump would cut out every time I tried to fill it up. By accident trying to learn how to test the purge solenoid on my 06, I determined the purge solenoid on the K3500 was bad and I replaced it and issue went away.

You can test the solenoid with a vacuum hand pump. It should hold like 20 in of mercury steadily. And applying 12 VDC the valve should open it. I almost always prefer to test things before replacing them. I've heard that sometimes even new replacement purge solenoids are bad, so the testing confirms this.

 

[petethepug]

It’s best to order the parts based on your own leg work. Can’t fault a forum member for providing a wrong part number based on potential variables neither of you were aware of.

RockAuto is usually my go to stop. Once I verify the part number(s) and pricing there, I make a list. With that list I Google the part numbers for better pricing.

R/A varies quite a bit on shipping charges because of where the part may be located. A $25 smoking hot deal on a R/A part my ship for $3 when combined with other parts but … the same part ordered all by itself if you forgot to include it in your 1st order could cost you $25 shipping later.

 

[rmaker]

I just dealt with this on my 2011 Suburban.

I replaced the following parts in this order.

Vapor Canister Vent Valve (in the back, connected to the charcoal can on one end). No improvement.

Vapor Canister Purge Valve Solenoid (in the engine bay/hose connected to it crumbled when replacing and was full of charcoal pellets). No improvement.

Charcoal Canister (in the back connected to fuel tank via EVAP lines and the vent valve, pellets just dumped out). No improvement.

EVAP Hoses/assembly (a series of plastic tubes/lines/hoses that sit on top of the fuel tank). Replacing this finally fixed it.

I can now pump fuel in without issue. I also put in a new fuel pump since the tank was dropped to replace the EVAP lines.

Pull the big line off the charcoal can, if it has charcoal pellets, your lines are gonna be full of those pellets. You can also pull the line on the EVAP solenoid in the engine bay, if there are charcoal pellets, your lines are clogged.

This guy has a series of three videos that describe in detail what the deal is.

https://youtube.com/@shopwarrior1835

 

[RocketcCutlass]

I just dealt with this on my 2011 Suburban.

I replaced the following parts in this order.

Vapor Canister Vent Valve (in the back, connected to the charcoal can on one end). No improvement.

Vapor Canister Purge Valve Solenoid (in the engine bay/hose connected to it crumbled when replacing and was full of charcoal pellets). No improvement.

Charcoal Canister (in the back connected to fuel tank via EVAP lines and the vent valve, pellets just dumped out). No improvement.

EVAP Hoses/assembly (a series of plastic tubes/lines/hoses that sit on top of the fuel tank). Replacing this finally fixed it.

I can now pump fuel in without issue. I also put in a new fuel pump since the tank was dropped to replace the EVAP lines.

Pull the big line off the charcoal can, if it has charcoal pellets, your lines are gonna be full of those pellets. You can also pull the line on the EVAP solenoid in the engine bay, if there are charcoal pellets, your lines are clogged.

This guy has a series of three videos that describe in detail what the deal is.

https://youtube.com/@shopwarrior1835

Thanks a lot. This was very helpful.

 

[petethepug]

Did ya get it wrapped up?

 

[olliec420]

I just dealt with this on my 2011 Suburban.

I replaced the following parts in this order.

Vapor Canister Vent Valve (in the back, connected to the charcoal can on one end). No improvement.

Vapor Canister Purge Valve Solenoid (in the engine bay/hose connected to it crumbled when replacing and was full of charcoal pellets). No improvement.

Charcoal Canister (in the back connected to fuel tank via EVAP lines and the vent valve, pellets just dumped out). No improvement.

EVAP Hoses/assembly (a series of plastic tubes/lines/hoses that sit on top of the fuel tank). Replacing this finally fixed it.

I can now pump fuel in without issue. I also put in a new fuel pump since the tank was dropped to replace the EVAP lines.

Pull the big line off the charcoal can, if it has charcoal pellets, your lines are gonna be full of those pellets. You can also pull the line on the EVAP solenoid in the engine bay, if there are charcoal pellets, your lines are clogged.

This guy has a series of three videos that describe in detail what the deal is.

https://youtube.com/@shopwarrior1835

I was able to use a shop vac and suck out the pellets out of the big line. May want to try that before ordering and taking fuel tank off.

 

[Geotrash]

I was able to use a shop vac and suck out the pellets out of the big line. May want to try that before ordering and taking fuel tank off.

This seems risky unless the shop vac has an explosion-proof motor.

 

[olliec420]

This seems risky unless the shop vac has an explosion-proof motor.

Well there is always that haha. I really should have done a video but I didnt know if it would work so I didnt bother. Basically I took the shop vac in one hand and the line in the other and would repeatedly butt the shop vac up to the other hand to make the best connection I could. I heard the pellets get sucked down the hose and kept doing it until I didnt hear anymore. Then blew (with my mouth) through the line successfully and could hear the air coming out the vent in the tank fill. Luckily that worked for me!

 

[Fless]

Wonder if one could do this with a compressor using the venturi effect on the end of the hose?