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| Home / Outboard Engines / Mercury Engines / Mercury 40 EFI |
Mercury 40 EFI Troubleshooting
| Engine won't start or starts hard |
No gasoline in tank - Add fuel.
Wrong fuel grade - Use quality fuel.
Air in fuel tank - Bleed fuel tank.
Damaged spark plug wiring connection - Check spark plug wiring connection, repair or change.
Faulty spark plug - Replace spark plug.
Dirty fuel filter - Fuel filter needs to be replaced.
Dirty fuel lines - Fuel lines must be clean.
Drained or worn battery - Charge or replace the battery.
Bad harness connections - Check electrical wire harness connections.
Ignition system is damaged - Check ignition components and replace if necessary.
Damaged pulse fuel pump - Change pulse fuel pump as required.
Defective electric fuel pump - Install new electric fuel pump.
Electronic control modul failure - Change electronic control modul.
| Engine starts and then stalls |
Damaged spark plug - Install new spark plug.
Ignition coil is defective - Install a new ignition coil.
Defective pulse fuel pump - Install new pulse fuel pump.
Fuel system is clogged - Clean fuel system.
Clogged final fuel filter - Final filter needs to be replaced.
Electric fuel pump failure - Change electric fuel pump.
| Engine runs unevenly |
Defective ignition system - Test ignition and replace failed parts.
Dirty or damaged fuel pump - Test fuel pump and replace if necessary.
Dirty fuel lines - Fuel lines must be clean.
Dirty fuel filter - Fuel filter needs to be replaced.
| Engine overheats |
Engine overloaded - Load reducing required.
Ignition timing is improper - Adjust ignition timing as required.
Faulty thermostat - Change thermostat.
Water pump failure - Replace water pump.
| Engine noises or knocks |
Stale or low octane fuel - Change gasoline.
Engine is overloaded - Load reducing required.
Incorrect low idle setting - Adjust idle speed.
Dirty or defective fuel pump - Test fuel pump and replace if necessary.
Crankshaft or main bearings wear - Worn parts replacement required.
Damaged piston rings or cylinder bore - Replace defective components.
| Engine power loss |
Fuel pump is defective or dirty - Inspect fuel pump and change as required.
Ignition failure - Check ignition and replace faulty components.
Damaged powerhead parts - Change defective parts.
Stator, coil, or switch box defective - Replace faulty parts.
Low compression - Normalize compression.
Fuel delivery problem - Check fuel system.
Manifold is leaking - Leak must be repaired.
Vapor separator flooding over - Normalize vapor separator functions.
| Engine uses too much fuel |
Spark plug is loose or faulty - Tighten or replace spark plug.
Worn sleeve, rings, or piston - Replace defective components as required.
Engine overloaded - Load reducing is recommended.
Fuel injectors are clogged or faulty - Clean or change fuel injectors.
| Trim motor is running but system can't move |
Low oil level - Check and refill oil.
Pump assembly is defective - Inspect pump and change as required.
Leakage of manual release valve - Valve need to be closed or changed.
Broken motor or pump driveshaft - Change worn component.
| Trim cannot be fully up or down |
Pump assembly faulty - Change pump as required.
Tilt ram piston ball is displaced - Service or repair.
Tilt ram piston O-ring damaged - Replace O-ring.
Oil insufficient - Need to add the oil.
Lower check valve not seating in port side trim ram - Install valve correctly.
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