1997 GMC Safari Owner's Manual - Page 263

When you put the cap back on, turn it to theright (clockwise) until you hear a clicking sound. Make sure you fully install the cap. The diagnostic system can determine if the fuel cap been left off or improperly has installed. This would allow fuel to evaporate intothe atmosphere. See"Malfunction Indicator Lamp" in the Index. Checking ThingsUnder the Hood I NOTICE: If you need a new cap, be sure toget the right type. Your dealer canget one for you. If you get the wrong type, it may not fit properly. This may cause your malfunction indicator lamp to light and your fuel tank andemissions system may be damaged. See "Malhnction IndicatorLamp" in the Index. Things that burncan get onhot engine parts and start a fire. These include liquids like gasoline, oil, coolant, brake fluid, windshield washer and other fluids, and plastic or rubber. You or others could be burned. Be careful not to drop or spill things that will burn onto a hot engine. 6-7