Sylvie Willis
Onan generators, or gensets, are a popular choice for RV owners. While Onan gensets are generally reliable, some models, such as the Marquis Onan 5.5, have been known to develop fuel seepage issues. To address this, some owners opt to install a fuel shut-off valve, which can be placed inline close to the carburetor. Additionally, regular exercise and treatment of the genset are recommended to prevent fuel-related problems and drive moisture out of the armature wiring. In terms of fuel lines, one Onan genset owner installed a 2-way valve in the fuel line, allowing them to switch between the RV's fuel tank and a standalone gas can.
| Characteristics | Values |
|---|---|
| Fuel line size | 3/8 to 1/2 tubing |
| Fuel type | Propane, gas, woodgas |
| Fuel pump | NAPA universal low-pressure fuel pump |
| Fuel shutoff valve | Yes |
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What You'll Learn
Fuel shutoff valve for Onan genset
Installing a fuel shut-off valve in your Onan genset is a viable option and will not cause any harm to the system. The Marquis Onan 5.5, in particular, has been known to develop a slight fuel seepage problem inside the genset housing. Therefore, installing a fuel shut-off valve can be beneficial.
Some users have also suggested that instead of plumbing in a fuel shut-off valve, you could shut off the little electric fuel pump that sits next to the generator. However, if you want to install a fuel shut-off valve inline close to the carburettor, you can do so. It is recommended to exercise the genset regularly, at least two hours per month, under as much load as possible, to prevent problems and keep the system running smoothly. This process helps drive moisture out of the armature wiring and heats up the power generation components.
Additionally, using products like Seafoam can help treat and maintain the carburettor. It is important to note that turning off the fuel will not completely empty the bowl but will only bring the fuel level down below the pilot jet. This means that some fuel may remain in the system even after shutting off the valve.
Overall, installing a fuel shut-off valve in an Onan genset can be a useful addition, providing insurance against fuel-related issues and allowing for better control over the fuel system.
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Onan genset fuel pump
The Onan genset fuel pump is a critical component of the generator's fuel system. It is responsible for delivering fuel from the tank to the engine, ensuring a consistent and controlled flow of fuel to the carburettor. The fuel pump plays a vital role in the overall performance and efficiency of the Onan genset.
Over time, the fuel pump may experience wear and tear, and in some cases, it may need to be replaced. There are several signs that indicate a potential issue with the fuel pump. For example, if the Onan genset struggles to start or stalls frequently, a faulty fuel pump could be the culprit. Other symptoms of a malfunctioning fuel pump include reduced power output, difficulty in maintaining a steady RPM, and increased fuel consumption.
When replacing the Onan genset fuel pump, it is essential to refer to the manufacturer's specifications and choose a compatible replacement part. The installation process typically involves disconnecting the old fuel pump, carefully removing it from the genset, and installing the new fuel pump in its place, ensuring all connections are secure and properly sealed.
Additionally, proper maintenance and care of the Onan genset fuel pump are crucial to ensure its longevity. This includes regular inspections and cleaning to prevent debris buildup and clogs. It is also recommended to use high-quality fuel and follow the recommended maintenance schedule to keep the fuel pump in optimal condition.
Furthermore, some Onan genset owners choose to install additional components, such as a fuel shut-off valve, to enhance the fuel system. This valve allows them to isolate the fuel supply, providing added control and peace of mind, especially during storage or transportation. It is always advisable to consult with a qualified technician or refer to the owner's manual before performing any modifications or repairs on the fuel pump or fuel system.
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Onan genset fuel line size
The fuel line size for an Onan 20ES genset is 3/8 to 1/2 tubing. This is likely to be for a high-pressure line (approximately 10 psi) feeding the second-stage regulator. If the second-stage regulator is mounted within a few feet of the set, a 3/4" iron pipe will be sufficient between the second-stage regulator and the demand regulator. It is important to have a fuel cut-off ahead of the demand regulator. A rubber (flexible) hose should be used between the demand regulator and the carburettor. The demand regulator is usually mounted to the base or somewhere besides the engine and needs to be "isolated" from engine movement.
The line size between the first-stage regulator at the tank and the second-stage regulator at the set will be determined by the distance from the tank. If the distance is under 100 feet, 1/2" (5/8" OD) copper should be adequate. You may be able to use 3/8" OD, but for a small difference in price, it is recommended to use 1/2".
It is worth noting that some Onan gensets have been known to develop a slight fuel seepage problem inside the genset housing. This can be addressed by exercising the genset regularly and treating the fuel with products such as Seafoam.
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Onan genset fuel seepage problem
The Marquis Onan 5.5 genset has been known to develop a slight fuel seepage problem inside the genset housing. This can be caused by a faulty fuel line or a damaged fuel shut-off valve.
To address this issue, carefully inspect the 90-degree elbow that the fuel line connects to at the carburetor for any signs of fuel staining. Ensure that the fuel line itself is intact and free of any rub marks or damage caused by contact with the oil cooler fins. If there are rub marks, it is recommended to cut a piece of slightly larger hose and place a "doubler" over the fuel line to protect it and prevent further damage. Additionally, check the fuel filter and set it to 90 degrees with a good pipe thread paste.
It is also worth noting that the fuel pump may be the cause of the issue. Onan fuel pumps are readily available on eBay, but it is important to select one with 2 to 4 lbs of pressure. Before replacing the pump, you can perform a simple test by placing the end of a length of hose in a gallon can of gas and observing if the fuel line on top of the tank has any cracks.
To prevent fuel seepage and maintain the genset's performance, it is recommended to exercise the unit for at least two hours every month under a significant load. This helps drive moisture out of the armature wiring and heats up the power generation components. Additionally, using fuel treatments such as Seafoam can help resolve and prevent fuel-related issues.
Finally, while converting from propane to gas on an Onan NHM Genset, it is important to be aware of the presence of a fuel cutoff solenoid between the pump and the carburetor in some models. This solenoid was removed in later specifications, but understanding its presence or absence is crucial when working on these systems.
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Onan genset fuel tank
The Onan genset fuel tank is an important component of the generator system, providing the fuel necessary for the genset to function. While there is limited information available specifically about the fuel tank, there are some key details worth noting.
Firstly, the fuel tank's capacity can vary depending on the model of the Onan genset. For example, some models, such as the Cummins Onan DGHE 50 KW, are often equipped with a 125-gallon base fuel tank. This capacity is designed to provide sufficient fuel for the generator's operation, ensuring it can run for extended periods without frequent refuelling.
Another important aspect of the Onan genset fuel tank is fuel delivery. The fuel line plays a crucial role in delivering fuel from the tank to the engine. Onan typically uses a rubber hose between the demand regulator and the carburettor. This demand regulator is usually mounted to the base or somewhere near the engine, isolated from engine movement. Ensuring the integrity of the fuel line is essential, as cracks or damage can lead to fuel leaks and air being sucked into the system, affecting the genset's performance.
In some instances, Onan gensets have encountered issues with fuel delivery from the main tank. This can be attributed to various factors, such as a faulty fuel pump or cracks in the fuel line. It is recommended to exercise the genset regularly, following the manufacturer's guidelines, to prevent moisture buildup in the armature wiring and maintain optimal performance.
Additionally, some Onan genset models have incorporated a fuel shut-off valve as a safety feature. This valve allows users to control the fuel supply to the engine, providing an extra layer of security. It is worth noting that installing a fuel shut-off valve is generally considered safe, and it can help address any concerns about fuel seepage within the genset housing.
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Frequently asked questions
Yes, you can place an inline fuel shutoff valve close to the carb on your Onan genset.
A fuel shutoff valve can help prevent fuel seepage problems inside the genset housing. It can also be used to run the bowl dry.
The fuel shutoff valve can be placed inline close to the carb or in a very handy place inside the genset housing.
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