I had a diesel, might not be true for Petrol cars, but I had a problem with a camshaft pulley pin. There is a groove on the camshaft where pin slides in and if it is broken off it would mean that the fuel is not supplied to the engine as the camshaft sensor is registering a different pattern/position than it used to be. In simple words, there has been an engine damage or the timing belt has slipped by a tooth or so causing an engine to ''shut down'' to prevent further damage. That would be the last 'thing that I would check as the timing belt has to come off in order to remove the pulley.
On the left: Broken off pin. On the right: Pin like it is supposed to be.
