Fuel Back Flow/Where Would You Start? - SOLVED

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ilikemikes

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Gentlemen, how would you start problem solving this without replacing everything? Gas is back flowing on last couple of trips to the gas station. No error codes except "tighten gas cap". 2011 Tahoe LT w/3inch body lift. TIA
 

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Read the specific code with a scanner; there can be a few codes that trigger the DIC message.

You likely have a plugged or inoperative vent valve (in the rear by the spare tire). Dirt gets into the breather filter and the solenoid can hang up. Worse than that, you could have a plugged evap canister and/or it has pushed carbon pellets into the evap lines. Start by getting the code, and testing the vent valve for proper operation. They can be intermittent.
 
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ilikemikes

ilikemikes

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Thanks for the quick response. I checked the vapor canister purge valve and seemed
to be in good order. Makes total sense to go to the back. I don't have a scanner. I'll probably order the vent valve OEM, replace it and watch for pellets.
 

petethepug

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2011 Tahoe LT. You’re on the right track for what to look at when you don’t have a scanner.

The good news is replacing those related vacuum / emissions items are due because of the age of the truck so you’re not really just throwing parts at it. A parts house or garage will also have a tester to verify if your gas cap lost its internal seal too.
 
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ilikemikes

ilikemikes

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Thank you and you are right...I just turned 172k miles. I won't hesitate to replace parts on my own but not going to let a dealer touch it. I'll try to use a scanner at a parts house.
 
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ilikemikes

ilikemikes

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Update...tested the vent valve solenoid with some current and got some really slow clicks in the unit. Tried blowing through it as well (supposed to be in open position) but it clogged with blowing. Moved on to the charcoal canister and removed. Pellets felt out but was able to blow air through this. Had a thought at this moment with vent and canister disconnected that I should try putting gas in. Same back flow issue.
Came home and ordered all the EVAP parts. When they get here on Tuesday, I'm going to drop the tank and blow the lines out before installing the new parts. Parts ordered are oem purge valve solenoid, oem vent valve solenoid, and dorman charcoal canister. Am I missing anything? Thx
 

Geotrash

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Update...tested the vent valve solenoid with some current and got some really slow clicks in the unit. Tried blowing through it as well (supposed to be in open position) but it clogged with blowing. Moved on to the charcoal canister and removed. Pellets felt out but was able to blow air through this. Had a thought at this moment with vent and canister disconnected that I should try putting gas in. Same back flow issue.
Came home and ordered all the EVAP parts. When they get here on Tuesday, I'm going to drop the tank and blow the lines out before installing the new parts. Parts ordered are oem purge valve solenoid, oem vent valve solenoid, and dorman charcoal canister. Am I missing anything? Thx
Bummer man. Glad you have a good handle on the work needed. Godspeed, sir.
 

petethepug

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OMG! You just blew 6 hours diagnostic time and $9h the dealership could of charged you. Fail!

Really though, you just hit the jackpot in heading off one of the biggest headaches in the 07-14 trucks. You can now order the OEM a/c Delco lifetime replacement fuel pump, carbon canister and fuel valve solenoid off rock auto or parts geek for about 3-$350 vs the $2k or higher the dealer or shoddy shop would charge you.

Get the parts and Sched some time to have an Indi shop do the job. Don’t forget to bring it in on an almost empty tank and if running e85, run a tank of Reg fuel b4 u bring it in. Make sure they blow out all the fuel lines and wipe out the tank for pellets. You’ll be good for another 100k mi and tank will fill up normally again.

These trucks sense regular gas only for the initial calibration and start up. If the initial start up is e85, it’ll buck like a tied up rodeo bull.
 
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ilikemikes

ilikemikes

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Solved! Dropped the tank (less than a 1/4 tank is key and easy) with a couple of jacks, one in front and one in back. Disconnect all the lines and ease the rear of the tank down first then the front. Blow all the lines out until they are completely clear and you see/hear air coming out. This took a little while with pellets lodged in the lines. Don't let those boogers (pellets) trick you, make sure lines are definitely clear and free flowing. Re-installed the tank, and installed new vapor canister, vent solenoid, purge valve and re-connected all lines. Yeah, I should of, would of and could of done a new fuel pump but I couldn't wait another 2 days for delivery. That tank drop was not bad. Any way, just went for the gas fill up test and all is well. I have to thank this forum for all the information do get this done.
 

Geotrash

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Solved! Dropped the tank (less than a 1/4 tank is key and easy) with a couple of jacks, one in front and one in back. Disconnect all the lines and ease the rear of the tank down first then the front. Blow all the lines out until they are completely clear and you see/hear air coming out. This took a little while with pellets lodged in the lines. Don't let those boogers (pellets) trick you, make sure lines are definitely clear and free flowing. Re-installed the tank, and installed new vapor canister, vent solenoid, purge valve and re-connected all lines. Yeah, I should have, would have and could have done a new fuel pump but I couldn't wait another 2 days for delivery. That tank drop was not bad. Any way, just went for the gas fill up test and all is well. I have to thank this forum for all the information do get this done.
Thanks for following up!
 

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