Ford Mustang Owner's Manual page 188

Since the circuit breaker for the headlamps is
mounted in the headlamp switch, you must
replace the entire switch to install a new circuit
breaker.
If the Engine Cranks but Does
Not Start or Does Not Start After
a Collision
Fuel Pump Shut-off Switch
If the engine cranks but does not start or does
not start after a collision, the fuel pump shut-off
switch may have been activated. The shut-off
switch is a device intended to stop the electric
fuel pump when your vehicle has been involved
in a substantial jolt.
Once the shut-off switch is activated, you must
reset the switch by hand before you can start
your vehicle. The switch is on the left side of the
trunk near the left tail lamp.
The fuel pump shut-off switch
190