Tohatsu MFS9.9E Troubleshooting
| Engine Model: Tohatsu MFS9.9E |
| Engine Type: 4-stroke 2-cylinder SOHC gasoline outboard engine |
| Total Displacement: 20.3 cu.in (333 cc) |
| Rated Engine Power: 9.9 Hp (7.3 kW) at 6000 rpm |
| Fuel System: Fuel Injection |
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| Engine hard to start or won't start |
Empty gas tank - Fill it up.
Wrong fuel grade - Use quality gasoline.
Air or water in fuel system - Remove water or air from fuel system.
Faulty spark plug wire connection - Check the spark plug wire connection, repair or replace.
Faulty spark plug - Replace spark plug.
Fuel filter is plugged - Replace or clean fuel filter.
Vapor separator needle valve is bend or wear - Replace needle valve.
Dirt in the fuel lines - Fuel lines must be clean.
Fuel tank air vent closed or restricted - Open or clean air vent.
Faulty fuel feed pump - Change or rebuild fuel feed pump.
Worn or improperly adjusted choke cable - Change cable or adjust properly.
Valve clearance is improper - Adjustment procedure required.
Incorrect valve timing - Set the valve timing correctly.
Fuel pressure is low - Inspect low pressure fuel pump or inspect fuel system for leaks.
Fuel injector is clogged or malfunction - Replace or clean as required.
Fuel regulator malfunction - Change fuel regulator.
ECM failure - Replace ECM.
| Engine starts but immediately stops |
Damaged spark plug - Change spark plug as required.
Worn or damaged vapor separator needle valve - Change vapor separator needle valve.
Ignition coil is faulty - Replace ignition coil as necessary.
Closed or restricted fuel tank air vent - Fuel tank air vent need to be opened or cleaned.
Faulty fuel pump - Repair or change fuel pump.
Damaged choke system - Check and repair choke system.
Incorrect valve clearance - Adjustment procedure required.
Wrong valve timing - Set the valve timing correctly.
Valve springs are loose or broken - Change valve springs.
Stuck valves - Service the valves.
Low cylinder compression - Check and change damaged parts.
Clogged fuel filter - Install new filter.
Dirty or faulty fuel injector - Clean or replace if necessary.
Insufficient engine oil - Check oil level and add oil as required.
Oil pump failure - Replace oil pump.
Water intake is blocked - Need to wash or clean.
Thermostat failure - Replace thermostat.
Water pump is defective - Replace water pump.
Defective ignition - Check ignition and replace faulty components.
Fuel pump is clogged or faulty - Check fuel pump and replace if necessary.
Worn or damaged vapor separator needle valve - Change vapor separator needle valve.
Fuel lines clogging - Fuel lines need to be cleaned.
Fuel tank air vent closed or restricted - Fuel tank air vent need to be opened or cleaned.
Dirty fuel filter - Fuel filter needs changing.
Intake manifold air leaks - Change intake manifold gasket.
Water intake is blocked - Clean and wash as required.
Throttle link and throttle valve are worn or damaged - Replace faulty parts.
Clogged or worn fuel injector - Replace or clean if necessary.
Engine overloaded - Load reducing required.
Fuel pump or fuel injector is clogged - Replace or clean if necessary.
Ignition timing is incorrect - Set the ignition timing correctly.
Thermostat is faulty - Change thermostat.
Water pump failure - Replace water pump.
Propeller selection improperly - Replace propeller.
Damaged or bent propeller - Have propeller repaired or replaced.
Outboard motor is mounted too high or too low - Position the engine correctly.
Engine oil insufficient - Fill up the engine oil.
Oil pump is defective - Change oil pump.
Water intake is clogged - Need to wash or clean.
Wrong valve setting - Valves needs to be set correctly.
Stale or low octane fuel - Change gasoline.
Engine overloaded - Load reducing required.
Low idle speed set incorrectly - Adjust as required.
Dirty or faulty fuel pump - Clean or change fuel pump.
Main bearings or crankshaft failure - Crankshaft or bearings need to be replaced.
Cylinder bore or piston rings are damaged - Change defective parts.
Dirt in the fuel lines - Clean fuel system lines.
Defective fuel injector - Test fuel injector and change if necessary.
Clogged or defective fuel pump - Service or replace fuel pump.
Ignition system is defective - Check ignition and replace faulty components.
Cylinder head gasket is defective - Cylinder-head gasket replacement required.
Faulty powerhead components - Defective parts need to be replaced.
Valves are stuck or burned - Service or change valves.
Propeller pitch or diameter incorrect - Replace propeller.
Damaged or bent propeller - Have propeller repaired or replaced.
Engine mounted at wrong transom height - Have motor adjusted to proper transom height.
Trim angle is incorrect - Adjust trim angle.
| Excessive fuel consumption |
Fuel injector is clogged or malfunction - Replace or clean if necessary.
Loose or defective spark plug - Re-tighten or change the spark plug.
Worn sleeve, piston, or rings - Change defective parts.
Electronic control unit failure - Install new ECU.
| Excessive engine vibration |
Damaged or improper size of propeller - Have propeller repaired or replaced.
Damaged propeller shaft - Replace propeller shaft.
Weeds wraped around propeller - Remove and clean propeller.
Motor mounting bolt is loose - Tighten bolt.
Steering pivot is loose or damaged Tighten or replace.
Low battery capacity - Battery needs to be recharged.
Battery discharges quickly - Service charging system or install new battery.
Wires are disconnected or battery terminals are corroded - Connect wires correctly or change terminals.
Defective starter motor - Repair or replace starter.
| Trim motor runs but trim system does not move up or down |
Insufficient oil - Need to add the oil.
Defective pump assembly - Inspect pump and change as required.
Manual shut-off valve leaks - Close the valve or change it.
Motor or pump driveshaft faulty - Replace worn component.
| Trim cannot be fully up or down |
Pump assembly is faulty - Replace pump.
Tilt ram piston ball is in wrong position - Service or repair.
Tilt ram piston O-ring damaged - Replace O-ring.
Oil level low - Check and refill oil.
Lower check valve not seating in port side trim ram - Secure valve properly.
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