Rebuilding Yanmar 2Qm15 Fuel Pump: Step-By-Step Guide

The Yanmar 2QM15 is a marine diesel engine. The high-pressure fuel pump in this engine can be rebuilt. Before starting the process, ensure that you have the necessary tools and safety equipment, as the fuel system is under pressure and diesel fuel is flammable and explosive. The steps to rebuild the high-pressure fuel pump include disconnecting the battery negative cable, closing the fuel supply valve, removing the intake manifold and alternator drive belt, disconnecting electrical connectors, fuel supply lines, and return lines, and finally, removing the high-pressure line and plug. It is important to refer to the service manual for detailed instructions and safety precautions when rebuilding the high-pressure fuel pump in a Yanmar 2QM15 engine.

Removing the fuel pump

To remove the fuel pump from a Yanmar BY Series engine, follow these steps:

Disconnect the battery

Disconnect the negative (-) cable from the battery. This is a standard safety precaution when working on any engine to prevent accidental electrical discharge.

Close the fuel supply valve

Locate the fuel supply valve at the fuel tank and close it. This will prevent any further fuel from being pumped into the system while you work.

Remove the intake manifold

The intake manifold needs to be removed to access the fuel pump. Refer to the Yanmar BY Series Service Manual for detailed instructions on this step.

Remove the alternator drive belt

Refer to the relevant sections of the service manual (11-7 and 7-21) for instructions on removing the alternator drive belt. This will provide access to the fuel pump and its connections.

Disconnect the electrical connector from the fuel measuring unit

Locate the electrical connector (Figure 6-20, (1)) and disconnect it from the fuel measuring unit.

Cap or plug all openings immediately

As you disconnect components, always cap or plug all openings to prevent contamination of the fuel system. This is crucial to avoid introducing dirt or debris into the sensitive fuel injection system.

Disconnect the fuel supply line

Disconnect the fuel supply line from the fuel pump, as shown in Figure 6-20, (2) of the service manual.

Remove the banjo bolt and disconnect the fuel return line

Remove the banjo bolt (Figure 6-20, (3)) and then disconnect the fuel return line. The banjo bolt is a type of fitting that connects the fuel lines to the pump.

Remove the high-pressure line between the pump and fuel rail

Using a special tool, remove the high-pressure line that connects the pump to the fuel rail (Figure 6-20, (4)). This line carries fuel at high pressure, so a special tool is required to ensure safe disconnection.

Remove the plug

Finally, remove the plug from the fuel pump, as indicated in Figure 6-21, (1) of the service manual.

At this point, the fuel pump should be accessible and ready for further maintenance or replacement. Remember to always refer to the official service manual for detailed instructions and safety precautions specific to your Yanmar engine model.

Disassembling the pump

To disassemble the high-pressure fuel pump on a Yanmar 2QM15, you will first need to address the fuel system. Place an approved container under the pump to catch the fuel, and wipe up any spills immediately. It is important to note that diesel fuel is flammable and explosive under certain conditions.

Next, you will need to disconnect the battery negative (-) cable. Close the fuel supply valve at the fuel tank and remove the intake manifold. Remove the alternator drive belt and disconnect the electrical connector from the fuel measuring unit. Cap or plug all openings to prevent contamination of the system.

Now, you can disconnect the fuel supply line and return line. Remove the banjo bolt and disconnect the fuel return line. Then, using a special tool, remove the high-pressure line between the pump and the fuel rail. Finally, remove the plug.

At this point, you should have access to the internal components of the high-pressure fuel pump and can proceed with the rebuild process. It is important to work carefully and methodically to avoid damaging any parts that can be reused.

Cleaning the pump

To clean the high-pressure fuel pump of a Yanmar 2QM15, you will need to first gather the necessary tools and materials, including a container to catch the fuel, rags, and eye protection. The process will involve several steps, including:

Step 1: Disconnect the Battery

Disconnect the battery negative (-) cable to ensure that there is no power running to the fuel pump during the cleaning process. This is an important safety precaution.

Step 2: Stop the Fuel Supply

Close the fuel supply valve at the fuel tank to prevent any further fuel from entering the pump during the cleaning process. This will help to avoid any spills or leaks.

Step 3: Remove Intake Manifold and Alternator Drive Belt

Remove the intake manifold and alternator drive belt to gain access to the fuel pump. This will involve loosening or removing bolts and carefully lifting the components away.

Step 4: Disconnect Electrical Connectors and Fuel Lines

Disconnect the electrical connector from the fuel measuring unit and cap or plug all openings to prevent contamination. Then, disconnect the fuel supply line and return line, followed by the high-pressure line between the pump and the fuel rail.

Step 5: Clean the Pump

With the fuel pump now accessible, use a suitable cleaning solution and a brush to clean the exterior and interior of the pump. Pay close attention to any nozzles, valves, or other small components, ensuring they are free of debris and buildup. You may also need to soak certain parts in a cleaning solution to loosen any stubborn deposits.

Step 6: Reassemble and Test

Once the pump is thoroughly cleaned, carefully reassemble all the components in the reverse order, ensuring that all connections are secure. Finally, reconnect the battery and turn on the fuel supply to test the pump. Ensure that there are no leaks and that the pump is functioning correctly.

It is important to note that working on a fuel pump can be dangerous due to the flammable nature of diesel fuel. Always take the necessary precautions and refer to a professional mechanic or the Yanmar service manual for detailed instructions if you are unsure about any steps.

Reassembling the pump

To reassemble the pump, you will need to reverse the steps you took to disassemble it, ensuring that all components are correctly aligned and secured. Here is a step-by-step guide:

Firstly, place the diaphragm and its retaining plate back into the pump, ensuring they are correctly positioned and secured. This is crucial to prevent fuel leaks and potential engine damage. Make sure the diaphragm is flat and not creased or folded, as this will affect its function.

Next, reattach the two halves of the pump, bolting them securely together while holding the pump arm in a depressed position. This will ensure the diaphragm is correctly seated and will prevent leaks.

Once the pump is reassembled, you can reattach the fuel lines, ensuring that all connections are tight and secure to prevent leaks. Reattach the banjo bolt and fuel return line, followed by the high-pressure line between the pump and the fuel rail, using a special tool for this step.

Reconnect the electrical connector to the fuel measuring unit, and ensure all openings are capped or plugged to prevent contamination of the fuel system. Reconnect the fuel supply line and the alternator drive belt.

Finally, reinstall the intake manifold and reconnect the battery negative cable. Be sure to follow safety precautions, such as wearing eye protection and placing an approved container under the pump to catch any spilled fuel.

Before starting the engine, be sure to bleed the fuel system to remove any air bubbles and ensure smooth fuel flow. Refer to your engine manual for specific instructions on bleeding the fuel system.

It is important to note that some components, such as the shim height and governor setup, are critical to the proper function of the pump and engine. Ensure these are correctly adjusted according to the manufacturer's specifications.

If you encounter any issues during reassembly or if you are unsure about any steps, it is recommended to consult a qualified mechanic or seek advice from online forums dedicated to Yanmar engines and sailing enthusiasts.

Reattaching the fuel pump

Step 1: Prepare the Engine

Before beginning any work on the fuel pump, it is important to ensure that the engine is properly prepared. This includes making sure that the engine is turned off and has cooled down completely. Place an approved container under the fuel pump to catch any spills, as diesel fuel can be flammable and explosive. It is also crucial to wear eye protection and cover the alternator with suitable materials to protect it from contamination.

Step 2: Disconnect the Battery

Disconnect the battery negative (-) cable to ensure that there is no power running through the engine during the repair process. This is an important safety precaution.

Step 3: Close the Fuel Supply Valve

Locate and close the fuel supply valve at the fuel tank. This will prevent any further fuel from entering the system while you are working on the pump.

Step 4: Remove the Intake Manifold

Using the appropriate tools and techniques, carefully remove the intake manifold. This will give you better access to the fuel pump and its components.

Step 5: Remove the Alternator Drive Belt

Remove the alternator drive belt following the instructions in the Yanmar 2QM15 service manual. This will allow you to access the fuel pump more easily.

Step 6: Disconnect Electrical Connections

Locate the electrical connector from the fuel measuring unit and carefully disconnect it. Immediately cap or plug all openings to prevent contamination of the fuel system.

Step 7: Disconnect the Fuel Supply Line

Identify the fuel supply line and carefully disconnect it. This will involve loosening any clamps or fittings that secure the line in place.

Step 8: Remove the Banjo Bolt

Remove the banjo bolt that secures the fuel return line. Again, be careful to catch any fuel that may spill during this process.

Step 9: Remove the High-Pressure Line

Using a special tool, remove the high-pressure line between the fuel pump and the fuel rail. This line is under high pressure, so exercise extreme caution during this step.

Step 10: Remove the Plug

Locate and remove the plug near the fuel pump. This will provide better access for the removal and reattachment of the fuel pump.

Step 11: Clean and Inspect the Fuel Pump

Before reattaching the fuel pump, it is important to clean it thoroughly and inspect it for any signs of damage or wear. Refer to the Yanmar 2QM15 service manual for detailed instructions on how to clean and inspect the fuel pump properly.

Step 12: Reattach the Fuel Pump

Carefully position the fuel pump back into place, ensuring that all connections and fittings are secure. Follow the steps in reverse to reconnect all the components that were removed earlier. Make sure that all openings are capped or plugged to prevent contamination.

Step 13: Test the Fuel Pump

Once the fuel pump is reattached, it is important to test it to ensure that it is functioning properly. Refer to the Yanmar 2QM15 service manual for specific instructions on how to test the fuel pump.

Step 14: Final Checks

After testing the fuel pump, perform final checks to ensure that all components are securely connected and there are no fuel leaks. Start the engine and observe for any unusual noises or performance issues. If everything appears normal, your fuel pump reattachment is complete.

Remember to exercise caution throughout the process and refer to the Yanmar 2QM15 service manual for detailed instructions and safety precautions specific to your engine.

Frequently asked questions