Will car start if timmin belt jumps?

No it will not start and if the timing belt has jumped you can severly damage the valve train in your engine by attempting to start it. The whole purpose of the timing belt is to make sure the valves open at the correct time during piston travel. Therefore if the timing belt has slipped your timing is going to be off by more than a couple of degrees and the piston is going to slam into the valve and bend the valve stem.