Suzuki outboard motors 1988 2003 repair manual., Page 96Get this manual
4-34 FUEL SYSTEM Air flows through the throttle body and surge tank to the intake manifold, where the intake air is mixed with combined fuelloil mixture that has been delivered through the fuel injectorThe throttle sensor assesses the throttle opening angle and sends the corresponding signal to the control unitFuel is drawn through the primer bulb to the low pressure fuel pumpUpon reaching the vapor separator, the gasoline is mixed with oil (supplied directly from the oil pump to the vapor separator) and the combined fuelloil mixture goes through the high-pressure fuel pump and delivery galleryThe pressure regulator maintains the fuel pressure in the feed line, from the high pressure fuel pump to the fuel injectorThis pressure, maintained at constant level, is higher than the manifold pressure (injector nozzle ambient pressure)When the higher fuel pressure in the feed line exceeds the pressure in the manifold by more than approximately 36.6 psi (2.55 kg-cm), the valve in the pressure regulator will open, thereby returning fuel to the vapor separator through the fuel return hoseThe fuelloil mixture is injected into the intake manifold by the fuel injector when the signal is supplied from the engine control unit (ECU)The electronic fuel injection control system is primarily based on the signals supplied from both the engine speed sensor (gear counter coil) and the throttle valve sensor (TPS)To compensate for other conditions, cylinder wall temperature sensor, air temperature sensor and atmospheric pressure sensor are also usedBased on these sensor signals, the engine control unit (ECU) determines the injection time duration and sends the injection signal to the injectorThe ECU's sequential multi-point programming provides individual control of each injector operating duration and timingAn additional feature of the Suzuki system is return-to-port capability or fail safe modeIf there is major sensor failure that prevents the ECU from processing, the engine is run on minimum performance mapIf either the counter coil or pulser coil fail, the ECU will not provide an injection signal without reference signal from these coilsUnder this condition, the engine can be cranked but it will not start without fuel injectionThe only input that will shut the engine down completely is battery voltageIf the battery is disconnected or the battery voltage falls below volts, the fuel pump quits pumping so the engine stopsThe Suzuki fuel injection system is divided into three component groupsThese are: Electronic control system Fuel system Air intake system The air induction and fuel systems are the delivery agents for the fuel air mixtureThe fuel delivery system is controlled by the electronic control systemThe electronic control system can be further subdivided into input sensors (the informants), outputs (the workers that make adjustments to fuel and timing), and the computer (the boss or decision maker) Electronic Control System