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Discussion Starter · #1 ·
The owner's manual says the fuel tank capacity for my vehicle is 21.7 gallons (AWD). I regularly put in 22 or 23 gallons, and recently put 24.5 gallons into the tank. This is not after running the tank dry or even close to it, so there are still a few gallons in the tank. I do continue to fill after the pump first shuts off though.

Anyone else have this experience? I wonder what the actual capacity is.
 

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Always the same gas station? Same pump? 21.7 Gallons is your tank capacity. If you are able to put in more than that you either have a major leak somewhere or the gas station has defective pumps.
 

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I never let it run all the way down, but after the pump shuts down I can squeeze in another 2 gallons at slow speed. No way to know exactly how many gallons are in the tank before filling up.
 

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Discussion Starter · #4 ·
Always the same gas station? Same pump? 21.7 Gallons is your tank capacity. If you are able to put in more than that you either have a major leak somewhere or the gas station has defective pumps.
No leaks, various gas stations, no defective pumps. I can put in up to 24 gallons with a couple of gallons still in the tank, so the actual capacity is more like 25 or 26.
 

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The fuel pump automatic shutoff prevents over filling which can cause a check engine light. Overfilling will cause issues with the fuel vapor canister.
 

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That's very true, which is why they probably rate the capacity at 21.7 gallons.
 

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my understanding....
overfilling. causes fuel to end up in the hose that goes to the carbon canister.
The carbon canister gets full of liquid fuel.
This fuel then makes it to the purge valve up front. The fuel and little pieces of carbon end up at the purge valve. This causes the solenoid to stick/fail.
So you end up with a liquid... where there should only be fumes.
 
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My 2020 FWD shows a capacity of 19.4 gallons. If I run the vehicle until the low fuel warning comes on, the fuel pump clicks off at 16 gallons. After which I can get an additional 4 gallons into the tank which totals 20 plus gallons plus whatever was still in the tank. It looks like they don't want owners overfilling the tank.
 

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my understanding....
overfilling. causes fuel to end up in the hose that goes to the carbon canister.
The carbon canister gets full of liquid fuel.
This fuel then makes it to the purge valve up front. The fuel and little pieces of carbon end up at the purge valve. This causes the solenoid to stick/fail.
So you end up with a liquid... where there should only be fumes.

Exactly. When it clicks off don’t continue to fill it or you will have major repair problems down the road.

The only vehicle I continue filling is my 05 vw diesel with a 15 gallon tank. When the nozzle clicks off I can usually get an additional 2 gallons in the tank. Which is the difference between around 600 miles per tank to around 800 miles per tank. My diesel doesn’t have a carbon canister.
 

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The owner's manual says the fuel tank capacity for my vehicle is 21.7 gallons (AWD). I regularly put in 22 or 23 gallons, and recently put 24.5 gallons into the tank. This is not after running the tank dry or even close to it, so there are still a few gallons in the tank. I do continue to fill after the pump first shuts off though.

Anyone else have this experience? I wonder what the actual capacity is.
Hello! The manufacturer,General Motor Corporation,(GMC) Has given you the SAFE!, capacity of your fuel tank, 22gals is fine, would not suggest continuing to overfill tank, the Evaporative and purge system relies on that extra room for fuel vapors to expand and contract with normal conditions such as weather, so to avoid costly repairs to your emission system and the safety and well-being of you and your passengers, please do not continue to see how much you can squeeze in that plastic fuel tank, if you smell gas you have a leak, Good luck! Be Safe!!
 

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Here's a excerpt from my manual. It indicates that three clicks is acceptable, which probably depends on the flow rate.

6758
Capture.PNG
 

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This big discrepancy in tank capacity, in my opinion is unregulated pumps. First of all I don’t let my tank run that low. I drove to Fla. and there were places in the state that the dates on the pumps were out dated by years. My car was taking numbers that I had never seen. Keep an eye on the dates on the pump. Your not taking the numbers that the pump is telling you.
 

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I tried my hardest yesterday to put more than 19 gallons in the tank in my 2018 FWD Enclave. I was still a little over E. The pump handle clicked off at about 17.5 gallons. I'd pull the handle and it would get a tiny bit more then click off. Did this several times until it spit fuel out. I got about 17.7 gallons in it before giving up.

I see no way that the vapor canister and associated lines can hold 3 additional gallons. It's just not physically possible. Plus, if fuel made it into the evap system, your CEL would certainly come on. I think you are getting cheated by unscrupulous private gas station owners.
 

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I agree that 3 gallons would be a stretch for the vapor canister and lines, but IF that were happening, as soon as the purge valve opened the vehicle would go super rich and most likely stall or at least badly misfire and as you stated, turn on the check engine light and set multiple misfire codes. As for the gas stations, I generally use 1 of 4 stations (2 Shell & 2 Mobil) all of which are fairly new (Less than 4 years old) and my fuel purchases are very consistent across the board. The only variable that I see are the pump and nozzle manufacturers. Some have much higher fuel flow and some nozzles are more sensitive which can affect the amount of fuel you dispense. Also the amount of pumps being used at the station at that time affects the fuel flow. If you really don't trust a pumps accuracy, buy a 1 gallon container and put in exactly 1 gallon of water and mark the container at that level. Then before you fill up your vehicle, put 1 gallon of fuel in the container to verify it's accurate.
 
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