Do you have the kind of pickup from the tank that is through a banjo fitting on the top of the tank, or a pipe that comes out of the plate that contains the wires for the sender?
If the former, then disconnect the banjo fitting and make sure there are no goobers blocking the small orifices in that connection. They can trap sealant or rust particles very easily.
The other possibility is that if this car sat for a long period of time with a low fuel level, then the pickup tube may have developed a pinhole due to corrosion.
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