1997 GMC Sonoma Owner's Manual - Page 244

NOTICE: If you get gasoline on yourself and then something ignites it, you could be badly burned. Gasoline can spray out on if you open the you fuel filler cap too quickly. This spray can happen if your tank is nearly full, and is morelikely in hot weather. Open the fuel filler cap slowly and wait for any "hiss" noise to stop. Then unscrew the cap all the way. Be careful not to spill gasoline. Clean gasoline from painted surfaces as soon as possible. See "Cleaning the Outside of Your Vehicle" in theIndex. When you put the cap back on, turn it to the right (clockwise) until you hear a clicking sound. Make sure you fully install the cap. The diagnostic system can determine if the fuel cap has been left off or improperly installed. This would allow fuel to evaporate intothe atmosphere. See "Malfunction Indicator Lamp" in the Index. If you need a new cap, be sure to get the right type. Your dealer can get one for If you get you. the wrong type, it may not fit properly. This may cause your malfunction indicator lamp to light and your fuel tank and emissions system may be damaged. See "Malfunction Indicator Lamp" in the Index. Checking Things Under the Hood 6-6