Mercury Mariner 200, 225 Optimax Outboards Service Manual, 90-855348, Page 188Get this manual
FUEL PRESSURE AND AIR PRESSURE TROUBLESHOOTING CHART PROBLEM Fuel Pressure and Air Pressure are Both Low CORRECTIVE ACTION 1Inspect air compressor air intake (air filter in flywheel cover) for blockage2Remove air compressor cylinder head and inspect for scuffing of cylinder wallInspect for broken reeds andor reed stops3Tracker ValveRemove and inspect diaphragm for cuts or tears4Air RegulatorRemove and inspect diaphragm for cuts or tears1Each time key is turned to the RUN position, the pump should operate for secondsIf it does not run, check 20 ampere fuse2If pump runs but has no fuel output, check vapor separator (remove drain plug) for fuel3If no fuel present in vapor separator, check fuelwater separator for debrisCheck crankcase mounted fuel pump for output4Check pump amperage drawNormal draw isamperes; if draw is below amperes, check fuel pump filter (base of pump) for debrisIf filter is clean, replace pumpIf amperage is above amperes, pump is defectivereplace pump5Fuel RegulatorRemove and inspect diaphragm for cuts or tears Fuel Pressure Low or Fuel Pressure Drops while Running (Air Pressure Remains Normal)