If you are unable to pull the pull start without the wheels turning it means your clutch shoes have probably melted. This happens when the car has been incorrectly adjusted so that the brake is slightly on when the throttle is in the neutral position. They can also melt if the wheels or truck is held still while the engine is revving or if the idle speed is to high. If this happens you will simply need to purchase a new clutch shoe and replace the melted one.