My opti manual -The fuel pump is a crankcase-pressure-operated, diaphragm-type pump. Crankcase pulsatingpressure (created by the up-and-down movement of piston) is transferred to fuelpump by way of a passage (hole) between crankcase and fuel pump.When piston is in an upward motion, a vacuum is created in the crankcase, thus pullingin on the fuel pump diaphragm. The inlet check valve (in fuel pump) is opened and fuel(from fuel tank) is drawn into fuel pump. Your Opti already has a water separatorThe warning system will turn on when water in the fuel filter reaches the full level.1. This filter removes moisture and also debris from the fuel. If the filter or filter chamberbecomes filled with water, the water can be removed. If the filter becomes pluggedwith debris, the filter must be replaced with a new filter.
.
