That sounds to me like your gas line is air locking over time.
On the stock setup, the gas filter has two outlets. The center one goes to the carb and the top one goes to the return line. If the return line isn't up top, the gas will syphon back over time, usually overnight though.
The gas pump also has an anti drain back valve that could be getting leaky.
One other thing that can air lock the line is a pinhole leak on the suction side of the pump. The rubber lines can crack or the steel line leak and just leave a stain. When sitting, it can let air in.
86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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