Where is the fuel reset button on a 1999 mercury mountaineers?

There isn't a fuel reset button on a 1999 Mercury Mountaineer (or most vehicles, for that matter). The fuel system doesn't operate on a simple resettable counter like some electronic devices.

If you're experiencing fuel-related issues, such as a check engine light related to the fuel system, you'll need to have the vehicle diagnosed by a mechanic. There's likely a problem with a sensor, fuel pump, fuel injectors, or another component within the fuel system. A simple "reset" won't fix an underlying mechanical or electrical problem.