It probably will NOT start AND will damage the engine! 2nd Answer It is true that if you try to start the engine, it won't start. But it won't damage your engine. This problem happens alot. When a belt breaks, only the lower part of the engine will actually rotate when you crank it, (like it was normally designed to do). However, the upper part (the camshaft where the 12 0r 16 valves are) won't rotate. The reason is that the belt is no longer attached to it bcuz it broke. When the belt is attached to the lower crankshaft and the upper camshaft, the pistens move up and down and the 12 or 16 valves open and close as it was designed to do. This is the result of when you put the key and start the engine. This is how engine parts operate: Key goes in and turns the sw. Power is applied to the starter The starter begins to turn the flywheel, which is attached to the engine. The flywheel is attached to the Lower Crankshaft, and so are the pistons and timing belt. As the crankshaft turns, the pistons begin an up and down movement. At the same time, (by means of the "TIMING BELT" which protrudes to the top of the engine and is attached to the upper Camshaft), the Camshaft also rotates. This in turn causes the valves to open and close. Also, the igniton or known as the distributor, has a rotor and is also rotated by this camshaft sending out electricity to each sparkplug wire and sparkplug. Now, the job of the valves, is to allow gas and air to enter and escape from the cyl. (piston chambers). So, when air and gas enter, the piston travels up on compression stroke..Meaning the gas and air are being compressed. Now, when this happens, the sparkplug fires in the cylinder/piston chamber and the piston is sent down on a power stroke, creating power for the transmission to use. So.. You can see that the timimg belt is an important part and needs careful attention when replacing. Hope this tour was of help. JP If you have a non interference engine nothing will be damaged and your car wont start. If you have a interference engine your pistons will hit and bend your valves therfore you will have to take your cylinder head off and replace valves and seats, headgasket and any other gaskets in the way to take the head off =$$$$ If you try to start the engine, nothing will happen, you will hear the car crank, but it wont start. If the timing belt breaks while you are driving, you will severely screw up your valves, unless you have a non-interference engine.