Ford Mustang Owner's Manual page 151

For a cold engine:
At temperatures 10˚F (-12˚C) and below: If
the engine does not start in fifteen (15)
seconds on the first try, turn the key to OFF,
wait approximately ten (10) seconds so you
do not flood the engine, then try again.
At temperatures above 10˚F (-12˚C): If the
engine does not start in five (5) seconds on
the first try, turn the key to OFF, wait
approximately ten (10) seconds so you do not
flood the engine, then try again.
For a warm engine:
Do not hold the key in the START position
for more than five (5) seconds at a time. If
the engine does not start within five (5)
seconds on the first try, turn the key to the
OFF position. Wait a few seconds after the
starter stops, then try again.
Whenever you start your vehicle, release the key
as soon as the engine starts. Excessive cranking
could damage the starter.
After you start the engine, let it idle for a few
seconds. Keep your foot on the brake pedal and
put the gearshift lever in gear. Release the
parking brake. Slowly release the brake pedal
and drive away in the normal manner.
NOTE: Your vehicle has an interlock that
prevents you from shifting out of P
(Park) unless your foot is on the brake
pedal.
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