GMC 1997 Safari Owner's Manual page 263

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 into the
atmosphere. See "Malfunction Indicator Lamp" in
the Index.
I
NOTICE:
If you need a new cap, be sure to get the right
type. Your dealer can get 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 and emissions system may be
damaged. See "Malhnction Indicator Lamp" in
the Index.
Checking Things Under the Hood
Things that burn can get on hot 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.
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