Sylvie Willis
Yanmar diesel engines are known for their performance and power. However, there may be times when you need to adjust the fuel flow to ensure optimal performance. This process involves tweaking the fuel controller capsule on the injection pump, which regulates fuel delivery to the engine. It's important to approach this adjustment with caution, as diesel fuel is highly flammable, and incorrect adjustments can lead to engine damage or safety hazards. Before making any changes, it is recommended to consult a qualified mechanic or a diesel service shop to ensure the necessary expertise and safety precautions are in place.
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What You'll Learn
Adjusting the fuel controller capsule
Firstly, locate the dot on the pump rack. This dot serves as a reference point for making the "factory" adjustment. It is important to note that adjusting the fuel controller capsule can impact fuel delivery, so understanding the direction of adjustment is crucial. Turning the screw in one direction can increase fuel delivery, while turning it in the opposite direction might hinder performance.
The next step is to identify the "smoke screw," which is typically located on the front of the injector pump. By turning out this screw, you can allow the engine to access more fuel under load while trying to reach full rpm. This adjustment enables the governor to open more freely, providing additional fuel when RPM starts to drop. It functions similarly to an accelerator pump on a carburetor.
To increase fuel flow, you can also adjust the fuel rack. Moving the rack to the left will increase the flow, while moving it to the right will shut off the fuel supply. This adjustment is part of the governor linkage, which is where the actual adjustment for fuel flow takes place, according to diesel service shop experts.
Additionally, consider adjusting the shim thickness between the injector pump housing and the block where the fuel lines attach. Reducing the shim thickness can give the pump a little more advance. Adjusting the smoke screw in combination with shim thickness adjustments can improve starting, idling, and provide more power under load.
It is important to note that these adjustments should be approached with caution. While they can enhance fuel delivery, they may also impact the overall performance of the engine. It is recommended to seek advice from experienced individuals or qualified diesel service shops before making any adjustments.
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Turning the smoke screw
Before adjusting the smoke screw, it is important to note that diesel fuel is highly flammable and explosive under certain conditions. Therefore, it is crucial to consult a tractor dealer or mechanic if you are unsure about any of the following steps.
To begin adjusting the smoke screw, first locate the injector pump. The smoke screw is situated at the front of this pump. Using a wrench, turn out the smoke screw. This action will allow for a greater fuel supply to the engine when it is under load.
It is worth noting that some sources advise against adjusting the smoke screw, stating that it may hinder overall performance. Instead, they suggest that increasing the shim thickness between the injector pump housing and the block where the fuel lines attach may be a more effective method. This adjustment gives the pump more advance, potentially improving fuel delivery.
Adjusting the smoke screw can be a delicate task, and it is important to proceed with caution. It is recommended to consult a qualified diesel mechanic or a diesel service shop if you are unsure about making any adjustments to your engine.
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Reducing shim thickness
To turn up the fuel on a Yanmar diesel engine, you can adjust the fuel injection pump. However, it is important to note that adjustments to the fuel injection pump should be made by a qualified professional to ensure the engine continues to meet all applicable emissions regulations.
One way to increase fuel delivery is by reducing the shim thickness between the injector pump housing and the block where the fuel lines attach. This gives the pump more advance. Shims are used to adjust the timing of the injection pump, with thinner shims advancing the timing. It is important to use the correct shim thickness for each engine to ensure proper timing.
In addition to reducing shim thickness, turning the "smoke screw" on the front of the injector pump can allow the engine to get more fuel under load. This screw is also associated with reducing smoke and improving starting and idling.
Another method to increase fuel delivery is by adjusting the fuel rack on the injection pump. Moving the rack to the left increases fuel flow, while moving it to the right shuts off the flow.
It is important to note that adjusting the fuel injection pump and reducing shim thickness may impact engine performance and should be done with caution. For example, one user reported that reducing shim thickness slowed down the engine speed. Additionally, a mechanic noted that the governor on some Yanmar diesel engines can stick, causing the engine to choke down or die under load. Therefore, it is recommended to consult a qualified technician or mechanic before making any adjustments to your Yanmar diesel engine.
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Checking for air leaks
Yanmar diesel engines are quite forgiving when it comes to sucking air. It takes a lot of air to cause a Yanmar engine to stall. However, if there is enough air in the system, the engine may not restart.
To check for air leaks in your Yanmar diesel engine, there are several methods and procedures you can follow:
Visual Inspection
Start by visually inspecting the fuel lines, filters, and connections for any signs of leaks or damage. Look for any cracks, paint issues, or loose components that may indicate a potential air leak. Pay close attention to areas around the fuel tank, fuel pump, injectors, and fuel lift pump.
Pressure Test
You can perform a pressure test to identify air leaks. Rig a priming ball in line with the fuel tank. With the engine off, build up pressure in the system, and you should be able to locate the leak. This method can help identify blockages or restrictions in the fuel lines.
Fluid Leak Detection
There are fluids available that can be mixed with the fuel to help identify leaks. These fluids fluoresce when viewed with an infrared torch, making it easier to spot leaks after running the engine. This method can help identify even microscopic leaks that may be allowing air into the system.
Use of Talcum Powder
Apply talcum powder to various components such as joints, bleed screws, screw-on filters, and the filter pump. The powder will help identify any areas where air is escaping. Be cautious not to over-tighten connections as this can also lead to leaks.
Fuel Jug Test
Fill a jug with diesel fuel and connect it directly to the inlet of your pre-filter. If the problem persists, start working backward towards the tank. Disconnect and reconnect the jug at each fitting until you locate the source of the air leak.
Bulb and Filter Inspection
If you have installed a bulb or changed a filter, ensure they are installed correctly and functioning properly. A faulty bulb or a blocked filter can cause air bubbles or restrict fuel flow, leading to engine performance issues.
Remember, air leaks in a diesel fuel system can be challenging to diagnose and may require a combination of these methods to accurately identify the source of the problem. If you are unsure, it is always best to consult a qualified diesel mechanic or seek advice from Yanmar specialists.
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Using the correct diesel fuel
Yanmar Marine has approved B5 Bio Diesel fuel for use across most of its recreational marine engines. B5 is blended with a maximum of 5% biodiesel and must conform to ASTM D6751 or ISO EN14214 specifications. However, biodiesel can adversely affect certain metal, rubber, and plastic components of engine fuel supply and return systems. Yanmar Marine recommends using Bio Diesel-compatible components to avoid deterioration and damage.
If you are unsure about using biodiesel, you can opt for standard diesel fuel. One option is to purchase diesel from a gas station and store it in a jerry can. This diesel is the same as the fuel sold at marinas but may be cheaper. However, it is important to ensure that the diesel is clean and free of water, as water in the fuel can cause issues with your engine.
Another consideration is the use of fuel additives. Some people use additives sold at marinas to improve the quality of their diesel fuel. However, it is worth checking if the same additives are available at roadside gas stations, as this could provide a more convenient and cost-effective solution.
Regardless of the type of diesel fuel you choose, it is important to follow the recommendations and guidelines provided by Yanmar for your specific engine model. This includes information on the correct fuel supply and return system materials to ensure the optimal performance and longevity of your engine.
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Frequently asked questions
There is a dot on the pump rack that you can line up to make the "factory" adjustment. To deliver more fuel, turn the screw on the front of the injector pump anti-clockwise. This component is often referred to as the "smoke screw".
Adjusting the smoke screw will allow the engine to access more fuel under load while attempting to regain full rpm. However, it is important to note that this adjustment may help or hinder overall performance. It is recommended that you consult a qualified fuel injection shop before making any adjustments.
Firstly, ensure that you are using the correct type of fuel. Only fill the fuel tank with diesel fuel, as gasoline may result in a fire and will damage the engine. Additionally, check the fuel level in the tank and ensure that it is sufficient to cover the fuel pickup and prevent air from being drawn into the system.
Observe the fuel discharge from the injector lines. The discharge should be strong and free of air bubbles, and the fuel bursts coming from the pipes should be roughly equal. If there is a significantly lower output on one or more of the pipes, it indicates a problem inside the injector pump.
