Abstract: A drive mechanism for a high pressure fuel pump on a vertically oriented engine present a compact arrangement while driving the pump at a desired speed tailored to the engine's size and fuel supply needs. The drive mechanism includes a small diameter drive pulley mounted above a rotor (e.g., a flywheel or a cam drive pulley). This position permits easily access to the drive pulley for repair, replacement and belt positioning. The small diameter drive pulley drives a larger diameter driven pulley coupled to the fuel pump. The size of the drive and driven pulleys are selected to achieve a reduction ratio suited to drive the high pressure fuel pump at a speed tailored to supply an appropriate amount of fuel to the fuel injectors at an effective pressure for injection. In addition, the smaller diameter of drive pulley, and consequently the smaller diameter of the driven pulley, reduces the size of the engine.