Fuel tank pressure problem

Recently purchased a used 2016 TRD off-road and very quickly found out that the vehicle would continuously shut the gas pump off if you attempted to fuel at more than an extremely slow pace. The gas attendant (in Oregon) commented that it seems as though someone syphoned from the tank, as they exhibit a similar issue. Additionally, while driving in hot weather, I have begun to hear air escaping from the gas cap during acceleration, or constant throttle. The sound is similar to a very quiet blow off valve... It would seem to me that the fuel cell is not able to properly relief pressure?

Does anybody have any clue where to start with this one? Thanks!

 

1. Check the cap, replace.
2. Check the filler neck for any damage.
That is where I would start

 

check filler neck for any/all obstructions
no reason the tank would be pressurized with the cap off adding fuel

the tank is vented
excess fuel is returned from the EFI back to the tank
possibly pressurizing the tank
the air U hear while driving could be an issue

make certain the vent is open

 

Evap system is supposed to vent gasses back through the system and burn them off. Is your Check Engine Light on?
Zim

 

Sounds like a clogged vent. My buddy went through a similar thing with his Tahoe.

 

No, I do not have any engine light. I have heard EVAP system a couple times due to clogged lines, and also a flapper valve that could be damaged within the fuel cell itself. Unfortunately I just moved and my tools have not arrived yet. I guess once they do, I'll drop the tank and check all the lines first.

 

You have a blocked vent, or a vent valve that’s not opening. Regs require Venting to atmosphere to be controlled (can’t remember specifics), but basically means you have a a few vents that are electronically controlled. It’s quite common for one to fail and exhibit the exact system’s you have.

edit, it’s not venting to atmosphere it’s venting to canister

 

Canister clogged from overfilling. No need to drop tank. Fix that and it fixes everything.

 

Would this be evident with crud and charcoal bits in the EVAP line? At what point would be whole canister be bad??

 

When the tank vent is clogged to a point where you cannot put gas in the tank.

 

I’m not 100% sure how the Tacoma tanks are designed, but to me, it sounds like two problems...

The ‘Slow filling of the tank at the gas station’ problem that the OP is describing sounds like the tube that goes from the top of the gas tank to the filler neck is pinched/twisted/blocked.
The ‘Hissing noise from the gas cap while driving’ problem sounds like the EVAP system is blocked somewhere and building a lot of pressure.

 

Did you ever fix this? I’m having the same issue. I’m about to get a new EVAP canister/system.

fuel tank is pressurizing and can’t fill it at any fast pace at the gas station

 

Have you had the fuel tank out or a fuel pump changed? Sometimes when the tank is put back the fill line gets crimped and fuel won’t flow smoothly into the tank. Just a thought I have had that issue on another vehicle.

 

Apologies for the much-overdue response!! Hopefully you fixed your issue by now, but I wanted to post my fix so others can hopefully benefit. The issue ended up being a clogged air vent for the EVAP canister. There is a "clam-shell" style air filter that is mounted to the fuel line just inboard of the fuel door (in between the bedside and bed itself). If you follow the vent line coming from the canister, you will certainly find it hiding up above the rear wheel well. I separated the filter halves, removed it from the fuel line and found it packed with dirt/dust. After I cleaned out the dirt, I sprayed the housing with compressed air ... re-installed everything and the issue is gone. For safe measure, I disconnected all EVAP lines from both at the charcoal canister and engine so I could blow them out with low PSI air and ensure they were not packed with any dirt. They were clean, so all signs point to the vent.

 

Sounds stupid, but get gas from a few different stations to check this. I've had this issue with 2 GMC Sierras over the years and both turned out to be the local Shell station pumps. I go to Shell because of their gas quality, but I've found some other top-tier gas stations nearby where this doesn't happen.

 

How did you reach this filter? Did you have to remove the bed? Ive been chasing an evap leak with codes that point to the evap canister. I get a lot of pressure buildup that releases when i remove the gas cap. I havent had issues refueling in about a year but i did use to have that problem.

 

No, I did not have to remove the bed. It was a few years ago, but if I remember correctly... I reached up from underneath the truck to disconnect the lines from the filter canister, then removed the fasteners that held the filler neck to the bedside. After that it was a bunch of wiggling things around in order to get hands-on and remove the filter canister. Wasn't fun.