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I suspect that you have a faulty fuel filler neck non-return fuel valve.
This is a little plastic one-way flapper valve in the fuel filler neck. Over time the plastic gets distorted and sticks in the closed position preventing gas from going into the gas tank.
Here is a diagram. Please let me know if you have any additional questions by hitting the reply button. Thanks
NONRETURN VALVE INSPECTION[LF, L3]
According to Mazda tech, all looked good with the fuel filler neck, however it is possible that it could have been missed. I should mention that my digital read out of how much fuel I have remaining creeps up very slowly after I attempt to put fuel into the tank - this usually takes me about 5 Min to get roughly 2 gallons in the tank. The read out will go up by single KM incriments, which says to me that some gas is getting in, be it very slowly.
Also more than once gas and air have gurggled out of the tank together while I have been attempting to put gas in.
Does this extra info lead you in another direction? Or do you still suspect the non return valve?
I still suspect a non-return valve as I stated before. If the valve is stuck closed, a small amount of gas will still enter the tank. It just takes a long time to fill that way.
The only way to check the valve is to remove the fuel filler tube and physically look and touch it.