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Test firing the fuel injectors on your Mercury 2.0, 2.4, 2.5, and 3.0 Liter EFI and DFI 2-Stroke Outboards (including most 4-strokes) engine with a test harness might be helpful in several ways:


Diagnosis: A test harness allows you to simulate engine conditions and observe the injectors' performance without the engine running. This provides a precise way to diagnose any issues. It allows for a controlled environment, reducing the risk of accidents or injuries.


Time Efficiency: Using a test harness saves time by quickly identifying faulty injectors without the need for extensive disassembly of the engine. You can fire injectors both on or off the motor, also dry with/or without fuel/cleaner running through them and it both both directions.


Consistency: A test harness ensures consistent testing conditions for all injectors, allowing for comparison and identification of any variations that might indicate a problem. It bypasses the ECU and the Engine Harness to isolate whether individual injectors are working properly.


Prevent Engine Damage: By testing injectors outside of the engine, you can prevent potential engine damage that might occur if a faulty injector is left unchecked and causes misfires or lean conditions.


Optimal Performance: Ensuring injectors are flowing and have a proper pray pattern helps maintain optimal engine performance. Properly functioning injectors provide the correct amount of fuel to the engine, improving fuel efficiency and reducing unnecessary fuel consumption.

By using a test harness to fire the fuel injectors on your Mercury 2-stroke EFI outboard engine, you ensure that your engine runs smoothly and efficiently, providing reliable performance and preventing costly repairs.


Functions simply by connecting to the 12-volt battery in the boat or even a small square household 9v battery.


This does not replace our Professional Injector Cleaner Service but allows you to quickly, easily, and cost-effectively understand a situation.

Injector Test Harness, Mercury 2-Stroke EFI

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