The fuel demand valve is an important component in boats with outboard motors, designed to prevent engine flooding and fuel spillage by controlling the flow of fuel to the engine. However, there have been concerns raised about the effectiveness of these valves, with some reports of fuel leakage and engine problems. This has led to questions about the durability and reliability of these valves, especially in older boats. The fuel demand valve is a relatively new addition to boats, and its performance is crucial for the safe and efficient operation of outboard motors.
What You'll Learn
- The fuel demand valve prevents a pressurized gas tank from pumping fuel into the outboard and the water
- The valve is installed in the fuel line between the portable tank and the primer bulb
- The Attwood 9300FDV7 Universal Fuel Demand Valve is a popular choice for boats
- The fuel demand valve can be prone to cracking and leakage
- The valve is designed to prevent volatile, smog-causing gas fumes from escaping into the air
The fuel demand valve prevents a pressurized gas tank from pumping fuel into the outboard and the water
The fuel demand valve is an important component in boats with outboard motors, particularly those with EPA-compliant, zero-emissions portable gas tanks. Its main function is to prevent a pressurized gas tank from pumping fuel into the outboard engine and, subsequently, into the water.
The issue arises due to the absence of a two-way vent in modern portable gas tanks. This vent used to allow the release of pressure and volatile, smog-causing gas fumes. However, without this vent, the tank can quickly build up pressure when exposed to heat from the sun, leading to a dangerous situation. The pressure causes the gas to be forced through the hose and into the outboard engine, which often lacks the necessary mechanisms to prevent the fuel from continuing its path.
This can result in gas pouring out of the outboard and into the water, or even into the boat owner's face when connecting the tank, creating a hazardous and messy situation. The fuel demand valve offers a solution to this problem.
The fuel demand valve is installed in the fuel line between the portable tank and the primer bulb. Its purpose is to regulate the pressure buildup in the tank by allowing fuel to flow to the outboard engine only when it is running and actively demanding fuel. This valve effectively contains the pressure within the tank, preventing it from reaching the engine when it is not in use.
By installing a fuel demand valve, boat owners can avoid the potential safety hazards and environmental concerns associated with uncontrolled fuel release. It is a relatively simple and inexpensive solution to a problem that has been inadvertently caused by well-intentioned emissions-reduction efforts.
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The valve is installed in the fuel line between the portable tank and the primer bulb
The fuel demand valve is installed in the fuel line between the portable tank and the primer bulb. This is done to prevent a pressurized gas tank from pumping fuel through your outboard and into the water.
The installation process is as follows:
- Disconnect the fuel line from the tank and engine, draining any gas inside into a suitable container.
- Mark the fuel line between the tank and primer bulb at least 8 inches away from the tank, then cut the hose.
- Slip a hose clamp on the cut end, then insert the hose barb of the valve, ensuring the arrow printed on the side points toward the engine.
- Secure the hose clamp over the hose barb and tighten.
- Reinstall the primer bulb, ensuring it is correctly oriented.
- Connect the fuel line to the tank and engine.
- Prime the fuel line by squeezing the primer bulb a few times, then test start the engine.
- Check for any leaks and tighten connections as necessary.
It is important to use good quality hose clamps made of 316 stainless steel to prevent sharp edges that can cut into the fuel line or your knuckles. Additionally, it is recommended to use a "no spray" connector at the gas tank end of the fuel line to prevent leaks.
The fuel demand valve is designed to contain the pressure buildup in the tank and only allow fuel to flow to the outboard when the engine is running. This solves the problem of gas pouring out of the outboard into the water or other areas, caused by the lack of a two-way vent in portable fuel tanks.
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The Attwood 9300FDV7 Universal Fuel Demand Valve is a popular choice for boats
The Attwood 9300FDV7 Fuel Demand Valve prevents engine flooding and fuel spillage by stopping pressurized fuel from reaching the engine. It allows only the amount of fuel requested by the engine and prevents a pressurized "slug" of fuel from entering the engine. This valve is easy to install, with some customers reporting that it works as expected and has a simple mechanism. It is also versatile and compatible with Ethanol-blended fuels.
However, some customers have reported issues with the Attwood 9300FDV7 Fuel Demand Valve, including constant leakage and cracks in the housing. Some reviews mention that the product freezes and cracks in below-freezing temperatures, while others state that it caused operating problems in the summer due to overpressure.
Overall, the Attwood 9300FDV7 Universal Fuel Demand Valve is a popular choice for boats due to its compatibility, ease of installation, and effectiveness in regulating fuel pressure. While some customers have experienced issues, the majority of reviews are positive, with many boaters finding it to be a reliable solution to their engine problems.
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The fuel demand valve can be prone to cracking and leakage
The fuel demand valve is a crucial component in preventing engine flooding and fuel spillage by stopping pressurized fuel from reaching the engine. However, it is not without its flaws. Some customers have reported issues with the valve, including constant leaks and cracks in the housing. This can lead to fuel leakage, which poses a fire hazard.
The cracking issue appears to be a common problem, with some users reporting that their valves developed cracks within a year of purchase. In one instance, a user noted that their valve cracked during its first few months of ownership. This issue can be attributed to the valve's plastic housing, which may not be durable enough to withstand the pressure and stresses it is subjected to.
Another factor that can contribute to the cracking and leakage is the presence of contaminants in the fuel. These contaminants can prevent the valve from reseating properly, leading to fuel leakage. Additionally, ethanol-blended fuels can also be a factor, as some users have reported issues with fuel lines when using these blends.
To address these issues, it is recommended to regularly inspect and replace the fuel demand valve, especially if it is more than two years old. Additionally, using fuel without ethanol and regularly cleaning the valve can help prevent contaminants from causing issues.
While the fuel demand valve is designed to regulate fuel pressure and prevent engine flooding, the cracking and leakage issues highlight the importance of proper maintenance and the need for more durable materials in the valve's construction.
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The valve is designed to prevent volatile, smog-causing gas fumes from escaping into the air
The pressure valve is an important safety feature in many systems, including boats, to prevent the release of volatile and smog-causing gas fumes. In the context of outboard fuel demand valves, the pressure valve plays a crucial role in maintaining the integrity of the fuel system and preventing environmental harm.
Outboard fuel demand valves are designed to address the issue of gas fumes escaping from portable fuel tanks used in boats with outboard motors. Traditionally, these fuel tanks had a two-way vent, typically a small screw-type fixture, that allowed gas fumes to escape, contributing to air pollution. To mitigate this, modern portable tanks have been designed without vents, preventing the release of smog-causing fumes into the air.
However, the absence of a vent creates a new challenge: pressure buildup in the tank due to heat exposure. As the tank heats up, the internal pressure forces gas to be pushed into the outboard motor, potentially causing it to spew gas inside the cowling and eventually dribble out. This can result in gas pouring into the water, driveway, or backyard, creating a hazardous situation.
To address this issue, a fuel-demand valve can be installed in the fuel line. This valve acts as a pressure relief mechanism, allowing gas to flow to the outboard motor only when the engine demands it, that is, when it is running. By containing the pressure buildup, the valve prevents gas from being forced into the outboard unintentionally.
The installation process for a fuel-demand valve typically involves disconnecting the fuel line from the tank and engine, draining the gas, and cutting the hose at a marked location. The valve is then inserted, ensuring proper orientation, and secured with hose clamps. This relatively inexpensive solution helps prevent gas from reaching the motor unless it is needed, reducing the risk of accidental spills.
In summary, the pressure valve in the context of outboard fuel demand valves serves as a critical component to prevent the release of volatile and smog-causing gas fumes. By regulating the flow of gas, the valve ensures that it reaches the outboard motor only when necessary, reducing environmental impact and enhancing the safety of boat operations.
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Frequently asked questions
A fuel demand valve is installed in the fuel line between the portable tank and the primer bulb. Its purpose is to contain the pressure buildup in the tank and allow fuel to flow to the outboard only when the engine demands it, i.e., when it is running.
Due to EPA compliance, portable gas tanks for outboard-powered boats are now designed without a two-way vent to prevent volatile, smog-causing gas fumes from escaping into the air. Without a vent, there is no way to release the pressure that builds up in the tank when exposed to the sun. This can lead to gas being forced through the hose and into the outboard, potentially causing a spill. A fuel demand valve prevents this by containing the pressure buildup.
To install a fuel demand valve, you will need to buy a valve and two hose clamps, as well as have a sharp knife or shears, a screwdriver or socket driver, and a glass container for capturing gasoline. The process involves disconnecting the fuel line, draining the gas, cutting the hose, and installing the valve and hose clamps.
Some users have reported issues with fuel demand valves, including leakage and cracking. It is recommended to inspect the valve regularly and replace it if necessary.
Fuel demand valves are available for purchase from marine dealerships and online retailers, such as Amazon.