Sylvie Willis
The Yanmar diesel engine is known to have issues with its fuel shut-off valve, with some users reporting that their engines would not shut down using the ignition switch. While some workarounds include cutting power to the circuit breaker panel, this is not ideal as it can cause the engine to shut down immediately. It is possible to bypass the fuel shut-off valve by removing the plunger or blocking the opening, but this is not recommended as it can be dangerous and may cause fuel to drain into the crankcase.
| Characteristics | Values |
|---|---|
| Yanmar diesel fuel shut-off valve type | Fuel shut-off solenoid |
| Models | 6LP, 4LH, 65HP, YM2220D, YM2310D, YM2402D, YM2420D |
| Location | In the fuel line, before the injection pump |
| Function | Prevents fuel from flowing while shutting the engine down to prevent backfiring |
| How to shut off the engine | Manual pull cord in the engine room, ignition switch |
| Fuel pressure | Around 4500 psi |
| Bypassing the solenoid | Possible by removing the plunger or blocking the opening |
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What You'll Learn
The function of the fuel shut-off solenoid
The fuel shut-off solenoid is an indispensable component in modern construction machinery and engine systems, including Yanmar diesel engines. It is a critical control element that significantly impacts the engine's fuel supply system. The solenoid operates on electromagnetic principles, allowing for the remote or automatic control of fuel flow to the engine.
When a suitable current is passed through the solenoid, it generates a strong magnetic field that attracts the solenoid plunger, pulling it toward the coil. The solenoid plunger is connected to the valve stem, so when it moves, it lifts the valve seat, allowing fuel to pass through the valve. This process is essential for the proper functioning of the engine. The diesel fuel shut-off solenoid opens the fuel valve when energized and closes it when deactivated, effectively managing the fuel supply.
In most cases, the fuel shut-off solenoid valve is a complete unit comprising two separate devices. The first device is the actual fuel shut-off mechanism, usually a traditional brass poppet valve. The valve operating rod is connected to a plunger that is typically mounted on a solenoid at the top of the valve body. When the diesel fuel shut-off solenoid is de-energized, the valve spring pulls the poppet back to its fixed position, firmly closing the valve. This action resets the diesel solenoid valve, preparing it for the next duty cycle.
The core components of the fuel shut-off solenoid are the electromagnet and the spool. It is important to ensure that the electromagnet generates a sufficient magnetic field when energized. Additionally, the spool should be inspected for any blockages, jams, or signs of wear. Regular cleaning and maintenance of the fuel shut-off solenoid are crucial, focusing on the valve core and valve body. This preventive measure can effectively prevent failures and ensure the proper functioning of the solenoid.
Troubleshooting a fuel shut-off solenoid requires careful inspection and addressing potential problems. It is important to ensure that the power connection is secure and that the wires are not damaged or broken. Verifying the control signal reaches the solenoid using appropriate tools is also necessary.
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Bypassing the solenoid by removing the plunger
Yanmar diesel engines use pull-type solenoids to control the shutdown of the engine. These solenoids have a plunger that moves in response to a magnetic field, which is created when an electrical current flows through the solenoid. When the plunger is pulled back into the solenoid body, the fuel supply to the engine is cut off, and the engine shuts down.
First, locate the solenoid. It is usually found in the fuel line before the injection pump. Once located, you will need to disconnect the power supply to the solenoid. This will involve identifying and disconnecting the correct wires, which should be done with caution as incorrect disconnection may damage the engine or create an accident risk. With the power supply disconnected, you can then remove the solenoid from the fuel line. This may require unscrewing or unbolting the solenoid, depending on its mounting configuration.
With the solenoid removed, you will have access to the plunger. Carefully take out the plunger, ensuring no damage is caused to the surrounding components. At this stage, it is crucial to note the orientation and position of the plunger for reinstallation if needed. With the plunger removed, the fuel supply will no longer be restricted by the solenoid, effectively bypassing it.
While this procedure may allow you to bypass the solenoid, it is important to emphasize that altering the fuel system in this manner may have unintended consequences, including safety hazards and engine damage. Proceed with caution and ensure you have the necessary skills and knowledge before attempting any modifications.
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Yanmar diesel engine won't turn off with the stop switch
If your Yanmar diesel engine won't turn off with the stop switch, there are several potential causes and solutions you can try.
Firstly, check that the tank fuel shut-off valve is open. If the valve is closed, the engine will continue to run until the fuel is manually shut off. This is a common issue, and simply opening the valve should resolve the problem.
Another potential cause could be an issue with the ignition switch wiring or the stop circuit. You can test this by putting a meter on the connection at the solenoid and pushing the stop button. If there is no signal, then the issue is likely with the wiring or the circuit.
In some cases, the stop lever may be sticking, preventing the solenoid from pulling it to the stop position. This can sometimes be resolved by manually pulling the lever and applying a shot of spray lube.
Additionally, it's important to check that the switch you use to start the engine is in the 'on' position. It is possible to accidentally turn it off, causing the engine to continue running while the electrics, such as the tach and engine time meter, are shut off.
Finally, some Yanmar diesel engines have a manual fuel shut-off lever that you can pull to kill the engine. This lever is typically located on the right side of the dash at the bottom. If your engine has this feature, you can use it to shut off the engine in case the stop switch is not responding.
If none of these solutions work, it may be necessary to consult a Yanmar technician or refer to the operating manual for further troubleshooting steps.
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Location of the manual fuel shut-off lever
The location of the manual fuel shut-off lever for Yanmar diesel engines varies depending on the model. For example, for the Yanmar 2GMF model, the fuel shut-off valve is built into the injector pump and is operated by a fuel shut-off cable attached to the bell crank at the injector pump.
For other Yanmar diesel engines, the manual fuel shut-off lever is typically located in the engine room and is attached to the fuel solenoid. In some cases, it may be a pull cord that needs to be pulled to shut down the engine. The exact location of the fuel solenoid is not always clear from the schematics, but it is generally located in the fuel line before the injection pump.
In one instance, a user reported that the manual fuel shut-off lever for their Yanmar diesel engine was located on the right side of the dash at the bottom. However, this may vary depending on the specific model and setup of the engine.
It is important to consult the operating manual and service manual for your specific Yanmar diesel engine model to determine the exact location of the manual fuel shut-off lever and to ensure proper use and maintenance. These manuals are often available online and can provide detailed schematics and instructions.
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Troubleshooting the solenoid and related issues
The Yanmar diesel engine may experience issues with shutting down the engine from the ignition switch. This could be due to a faulty three-way switch, which is typically in the "run" (middle) position and requires pushing up to start and down to shut off. If pushing down on the switch does not shut off the engine, the issue may lie with the switch or power supply. To confirm this, you can try cutting power to the circuit at the breaker panel, which should immediately shut down the engine. If the engine shuts down with the power cut, it confirms a switch or power issue.
Another potential issue could be related to the fuel solenoid. Some Yanmar engines have a manual pull cord in the engine room attached to the fuel solenoid to shut down the engine. If your engine has a similar setup, ensure that the pull cord is functioning properly. Additionally, check the operating manual and service manual for your specific Yanmar model, as they may provide schematic information about the valve and its location. The valve is likely located in the fuel line before the injection pump.
For the Yanmar 6LP model, the stop solenoid is located in the injection pump, and it requires 12vdc to run. If you are experiencing issues with the engine not shutting off immediately, you can use a meter to check the plug for any issues. Ensure that there is power to the solenoid, as a lack of power could indicate an issue with the switch or a potential relay issue between the switch and the solenoid.
Additionally, some Yanmar models, such as the 4LH, have a square black relay with prongs that need to be cleaned annually. Start by locating the stop solenoid and following the harness back to check for any issues. If there is a relay between the switch and the solenoid, a faulty relay could impact the engine's ability to shut down properly.
Finally, for some Yanmar models, the fuel shut-off may be related to the throttle lever position. Ensure that the throttle lever is in the correct position to shut off the fuel supply at the pump. This could be a factor in preventing the engine from shutting down properly.
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Frequently asked questions
Most Yanmar models have a manual fuel shut-off lever that you pull to kill the engine. This is usually located on the right side of the dash at the bottom.
The fuel shut-off solenoid prevents fuel from flowing while the engine is shutting down to prevent backfiring while the engine is still turning but the ignition is off.
Yes, theoretically, you can bypass the fuel shut-off solenoid. You can either remove the plunger from the solenoid or block the opening where the solenoid would be if removed. However, this is not recommended as the solenoid serves an important function.
Bypassing the solenoid may cause fuel to drain into the crankcase if the needle seat fails in a float bowl carb. It may also cause extended cranking times for the next cold start.
