Any idea where the shop looked? Did they even look at your Grand Cherokee? I'd start with a visual inspection. Allow the car to idle for a few minutes, then shut it off. Follow the fuel lines from the gas tank toward the engine, and look for any puddle or drips of fluid (may or may not be fuel, but make note of it's location). USE A FLASHLIGHT or L.E.D. FLASHLIGHT! Working with an exposed glass light bulb has the potential to break and ignite gasoline vapors. You may have to repeat the idle/shutdown process a few times if you don't find a leak right away. Gasoline vapors do evaporate quickly in warm/hot environments, which means any small puddle or drips may only be present for a short time.
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