hey guys I had this problem too, mine had problems even pumping gas for more then 5seconds, but once I got it to go after getting about 5gallons in it would overflow when full, check your ESIM, its the white plastic thing connected to the evap canister, there are 2 valves in it mine was cracked
The system is used to remove excess fuel tank vapors. this is done while the vehicle is being refueled.
Fuel flowing into the fuel filler tube creates an aspiration effect drawing air into the fuel fill tube. During refueling, the fuel tank is vented to the EVAP canister to capture escaping vapors. With air clowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the EVAP canister, the vehicles computer controlled purge system draws vapor out of the canister for the engine to burn. The vapor flow is metered by the purge solenoid so that there is no, or minimal impact on driveability or tailpipe emissions.
As fuel starts to flow through the fuel filler tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve and on to the vapor canister. Vapor is absorbed in the EVAP canister until vapor flow in the line stops. this stoppage occurs following fuel shutoff, or by having the fuel level in the tank rise enough to close the control valve. This control valve contains a float that rises to seal the large diameter vent path to the EVAP canister. At this point in the refueling process, fuel tank pressure increases,the check valve closes,(preventing liquid fuel from spiting back at the operator) and fuel then rises up the fuel filler tube to shut off the dispensing nozzle.
the check valves are in the ESIM switch, it comes off by pressing in on it and twisting counter clockwise 1/4 turn, no tools even needed.
Also everyone who has relocated their EVAP make sure your esim switch is mounted so that the wires that plug into it are in the 3 o'clock position, the check valves will not operate properly if the evap isnt mounted correctly. It also cannot be mounted on an angle, though I am pretty sure no one has theirs mounted like that.
the part is only 10 bucks, part # 4891685-AA Detector Evap
Hope it works for some of you.