Replacing The Fuel Pump On A 90 Hp 2-Stroke Engine

If you're experiencing issues with your 90 hp 2-stroke outboard engine, you may need to replace the fuel pump. This is a relatively straightforward process, but it's important to ensure you have the correct parts and tools before beginning. You can find fuel pumps compatible with your engine online or at marine supply stores. Before starting, make sure you have a new fuel pump, basic hand tools, and personal protective equipment, including gloves and eye protection.

First, locate the fuel pump on your engine. It is usually found near the fuel tank or the engine block. Once you have located the fuel pump, disconnect the fuel lines and electrical connectors, if any. Securely clamp the fuel lines to prevent fuel leakage. Then, remove the mounting bolts or brackets holding the fuel pump in place and carefully lift it out.

Next, compare the new fuel pump with the old one to ensure they are identical. Pay close attention to the inlet and outlet ports, as well as the mounting holes. If they are not aligned, you may need to modify the new fuel pump or adjust the fuel lines accordingly.

Now, carefully install the new fuel pump, ensuring that the inlet and outlet ports are correctly connected to the fuel lines. Secure the fuel pump in place with the mounting bolts or brackets. Reattach any electrical connectors and ensure they are properly seated.

Finally, inspect your work for any signs of fuel leaks or loose connections. Once you are satisfied, start the engine and check for proper fuel flow and pressure. If everything is functioning correctly, you have successfully replaced the fuel pump on your 90 hp 2-stroke engine.

Check the battery and listen out for the sound of the fuel pump engaging

When you try to start your engine, you should be able to hear the sound of the fuel pump engaging. If you can't hear this familiar sound, there's a chance that your battery is running low or there is an issue with it.

To check the battery, you can start by inspecting the battery terminals for any signs of corrosion or damage. Ensure that the connections are tight and secure. If the battery appears to be in good condition, the next step is to test it with a voltmeter or a multimeter. A voltmeter will allow you to measure the voltage of the battery, while a multimeter can test both the voltage and the current.

Connect the voltmeter or multimeter to the battery terminals, following the instructions provided with your testing device. The voltmeter should be connected in parallel with the battery, while the multimeter should be set to the appropriate setting, typically 20 DC volts or higher.

Take a voltage reading from the battery. A fully charged 12-volt battery should measure between 12.6 and 12.8 volts. If the reading is below 12 volts, your battery is discharged and may need to be replaced or recharged.

If your battery appears to be in good condition and is fully charged, but you still don't hear the fuel pump engaging, there could be other issues with the fuel pump or related systems. It is recommended to consult a professional mechanic or refer to specific troubleshooting guides for further diagnosis.

Check for slowing, stopping or sputtering

If your 90 hp 2-stroke engine is slowing, stopping, or sputtering, it could be due to a variety of issues. Here are some troubleshooting steps and potential causes to consider:

Check the Fuel System

As 2-stroke engines rely on a consistent fuel supply, issues with the fuel system are a common cause of engine problems. Here are some specific things to check:

• Fuel Tank Filter: Ensure that the fuel tank filter is clear and free from blockages. Replace the filter if necessary.
• Fuel Tank Cap: The fuel tank cap has a one-way valve that allows air to enter the tank. If this valve isn't working properly, it can create a vacuum lock, preventing fuel from leaving the tank. Try slightly unscrewing the cap to allow air to enter and see if that improves engine performance.
• Fuel Pipe: Inspect the external fuel pipe for any ruptures or damage. Drawing in air through these ruptures can affect the fuel-to-air ratio, causing the engine to bog down.
• Fuel Pump: Check the fuel pump for any issues. This includes inspecting the cap that keeps the diaphragm in place, as a loose cap or a loose screw can cause excess fuel spillage and air to be drawn into the carburettor. Additionally, problems with the fuel pump diaphragm itself, such as aging or the use of substandard materials, can reduce pumping efficiency.
• Fuel Vein Blockage: Even small pieces of debris that get past the fuel filter can cause issues in the fuel veins, eventually leading to a complete stoppage of fuel to the engine. If you suspect a blockage, strip down the carburettor and blow compressed air through the fuel veins to clear any obstructions.
• Fuel Line Connections: Inspect all fuel lines for loose connections, damage, or leakage issues. A punctured or degraded fuel line can cause air leaks, resulting in fluctuations in fuel supply and affecting engine performance.

Other Potential Causes

While fuel system issues are a common cause of engine problems, there are other factors to consider as well:

• Spark Plug Wiring: Corroded or fouled spark plug wires can cause the engine to sputter or lose power. Check the wires for any signs of corrosion or damage and replace the spark plugs if necessary.
• Propeller: Entanglement with debris or a spun prop (damage to the bond between the propeller and prop shaft) can affect the boat's ability to reach top speed. Regularly inspect the propeller and clear any debris.
• Idle Mixture Screw: Check if the idle mixture screw is out of adjustment, as this can impact engine performance.
• Thermal Relief Valve: A jammed or closed thermal relief valve can cause the engine to run rich at idle, while a stuck-open valve can result in cold-start characteristics.
• Anti-Siphon Valve and Fuel Pump Pressure: Refer to your outboard motor's service manual to check for issues with the anti-siphon valve and low fuel pump pressure.
• Battery Connections: Loose battery connections can affect engine performance. Ensure that all battery connections are secure and properly tightened.

If you've checked for these issues and are still experiencing problems, you may need to consult a qualified marine mechanic for further diagnosis and repair.

Check for rapid fuel use

Checking for Rapid Fuel Use

Rapid fuel use is a common symptom of a bad fuel pump. If you're burning through your fuel faster than usual, it's a sign that the condition of your fuel pump has deteriorated. It's a good idea to be aware of how long a tank of gas usually lasts you. If you notice that your tank is emptying faster than usual, it's time to check your fuel system for issues.

Common Causes of Rapid Fuel Use

• Dirty fuel filter – A dirty fuel filter restricts the flow of clean fuel, resulting in an insufficient fuel supply. This can cause the engine to stall or run poorly. Signs of a dirty fuel filter include slower engine speeds at full throttle, difficulty starting the engine when cold, and slow momentum and power build-up.
• Damaged fuel pump – A damaged fuel pump won't supply enough fuel for each combustion cycle, leading to engine malfunction, stalling, or poor performance. Unusual noises from the engine compartment, a check engine light, and lack of power when accelerating are all signs of a damaged fuel pump.
• Ruptured fuel pipe – A punctured fuel pipe will leak fuel, leading to poor engine performance. Signs of a ruptured fuel pipe include fuel leakage, a check engine light, erratic engine behaviour, and black smoke from the engine.
• Defective fuel pressure regulator – The fuel pressure regulator controls the amount of gasoline entering the engine's carburetor. If it malfunctions, it won't regulate fuel flow properly, leading to poor engine performance or stalling.
• Clogged fuel line – The fuel line delivers gasoline from the tank to the carburetor. A clogged fuel line will result in insufficient fuel supply, causing the engine to stall or run poorly. Signs of a clogged fuel line include sudden loss of power, difficulty idling, and fluctuating idle speed.
• Stuck fuel injector – The fuel injector supplies fuel to the engine. If it's stuck, the engine won't receive enough fuel. A rough idle and misfiring are common symptoms of a stuck injector.
• Damaged fuel pressure sensor – The fuel pressure sensor works with the fuel pump to deliver fuel to the engine. If it's damaged, the engine will lose power or stall.

Testing and Fixing Rapid Fuel Use Issues

To diagnose and address rapid fuel use issues, you can take the following steps:

• Clean the fuel filter – Inspect, service, or replace the fuel filter regularly to prevent clogging and ensure optimal fuel flow.
• Replace the fuel pump – If your engine still isn't getting enough fuel after cleaning the fuel filter, inspect or replace the fuel pump. Also, check for leaks and ensure the oil is not contaminated.
• Replace damaged fuel line – Over time, the fuel line can become damaged or clogged. Inspect the fuel line for damage or obstructions and replace if necessary.
• Replace a stuck injector – If the injector is stuck, carefully remove it and examine it for signs of corrosion or damage. Replace if necessary, then reassemble and test the engine.
• Rid the fuel line of dirt and debris – Check the fuel line for obstructions and remove any blockages immediately.
• Replace a defective fuel pressure regulator – If you suspect the fuel pressure regulator is defective, remove it from the gas tank and test it by turning on the ignition switch. If it doesn't turn smoothly, it's likely defective and needs replacement.
• Replace the fuel pressure sensor – If you suspect a damaged fuel pressure sensor, disconnect the fuel line and electrical power cable, then remove and replace the sensor.

Check the temperature gauge for a rise in temperature

Checking the temperature gauge for a rise in temperature is an important step in troubleshooting a faulty fuel pump on an outboard motor. Here are some detailed instructions on how to perform this task:

Locate the Temperature Gauge: The temperature gauge is usually located on the dashboard of your vehicle. This gauge indicates the temperature of your engine's coolant, letting you know if it is cold, normal, or overheating.

Understand Normal Temperature Readings: On most vehicles, the temperature gauge will read cold when the engine is first started and will gradually move towards the normal range as the engine heats up. This is especially true during cold winter months.

Identify a Rise in Temperature: If the temperature gauge continues to rise and exceeds the normal range, it could be an indication of a failing fuel pump or other issues. A high temperature reading may also be caused by a coolant leak, a faulty thermostat, or a damaged water pump.

Address the Issue: If the temperature gauge reads hot, it is important to take immediate action. Stop running your vehicle and call for a tow service to avoid further damage to your engine. Have a mechanic inspect your vehicle to diagnose and address the issue.

Additionally, when checking the temperature gauge, it is important to ensure that the gauge itself is functioning correctly. You can do this by testing the gauge using a pot of water on a stove and monitoring the needle's movement as the water temperature changes. This will help ensure that the temperature readings are accurate.

By regularly monitoring the temperature gauge and addressing any rises in temperature, you can help prevent serious engine damage and maintain the overall health of your outboard motor.

Test the fuel pump

Testing the fuel pump on your 90 hp 2-stroke engine can be done through a series of electrical and fuel pressure tests. Here is a step-by-step guide on how to perform these tests:

Electrical Test:

• Check the Fuel Pump Fuse: Refer to your owner's manual to locate the fuse box. Find the fuse associated with the fuel pump and inspect it for any signs of failure, such as a blown, broken, or burned fuse. If the fuse appears damaged, replace it with one of the proper amp rating.
• Check Voltage at the Pump: Consult your vehicle's service manual to determine the correct procedure for checking voltage at the fuel pump. Test for source voltage to ensure that the charge from the fuse is reaching the pump. If there is no power at the pump, move on to the next step.
• Test the Fuel Pump Relay Circuit: A lack of power at the fuel pump could indicate a faulty relay. Check the fuel pump relay circuit and consider replacing the relay if necessary.
• Perform a Drop Test: Using a voltmeter, check the power wire for full voltage and verify that the grounding wire is properly grounded. If this test does not reveal any issues, it is likely that the fuel pump needs to be replaced.

Fuel Pressure Test:

• Eliminate the Filter as a Possible Cause: Remove the fuel filter from the vehicle and drain any excess fuel. Use a short rubber hose on the filter inlet and blow through it, checking for minimal resistance. Inspect the screen for any debris, and replace the filter if necessary.
• Obtain a Fuel Pressure Gauge: Fuel pressure gauges are commonly available at auto parts stores or can be borrowed from machine or auto shops.
• Hook up the Pressure Gauge: Locate the fuel pump test point near the fuel injectors and the connection point between the pump and the filter injector rail. Attach the pressure gauge to the test port or separation joint.
• Rev the Engine and Check Pressure: With the engine slightly warmed up, have an assistant rev the engine while you monitor the pressure gauge. Check the pressure at idle speed and the rated speed specified in your pump specifications. If the pressure does not increase or remains below specifications, it indicates a faulty fuel pump.

If the electrical and fuel pressure tests reveal issues, it is likely that your fuel pump requires replacement or repair.

Frequently asked questions