[Sans Peur]

If you are blowing in and no bubbling it is possible that the pick up tube is broken off. Over time especially if you keep the tank low on fuel it can break off. With lower fuel levels more fuel movement is possible and while it is sloshing back and forth it will put a lot of pressure on the lower end of the tube and cause more torque on it.

Remove the fuel sender and see if you can use a flashlight to look in and view the pickup tube. You may need to buy a lighted flexable scope. I have one that Bluetooths into my cell phone.