Probably the fuel cut-off inertia switch has been activated. Reset the switch by firmly depressing its button.
Probably located in the left hand (near-side) rear corner of the engine compartment (behind the front suspension turret). It is on a 206 (early models only), and is likely to be the same on your 306.
Good luck, let us know how you get on.
ChicksFan
March 2010