Ameer Randolph
Running dual fuel tanks is a popular choice for 4WD users, especially those opting for green fuels like biodiesel and vegetable oil. A dual tank system offers flexibility and increased mileage. When installing a dual fuel tank, a six-port valve is crucial to prevent tank overflow and contamination between tanks. The setup involves dual in and out lines for each tank, with the ability to switch between supply and return lines. Proper filtration is essential to prevent failures caused by particulate matter. Some users opt for transfer pumps and timed switches to automate the process of switching between tanks.
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What You'll Learn
Using a six-port valve to prevent overflow and contamination
When running twin tanks, a six-port valve is of great importance. This valve is capable of switching both engine supply and return lines, preventing tank overflows and contamination between the tanks.
The six-port valve works by having a single output line to the engine and a single return line from the engine. Ports 1 and 2 take fuel from fuel tanks A and B. Port 3 delivers fuel to the engine, and port 4 receives unused fuel back from the engine. Finally, ports 5 and 6 return the unused fuel to the correct tank, preventing overflow and contamination. This is particularly important when running dual fuels, such as SVO or biodiesel, where one fuel type needs to be isolated to a single tank.
The Pollak six-port valve is considered the gold standard for twin tank systems. It is made in the USA and is a trusted and reliable unit. Being sealed and waterproof, it is ideal for 4WD and 4x4 applications. The Pollak valve is also supplied with moulded hose nipples, minimising the opportunity for leak points.
To trigger a change in valve position, a DPDT On-On switch is required and is often dash-mounted. It is important to note that the gear tolerances are minimal, and any particulate matter such as rust from fuel tanks can build up and cause failure. Therefore, it is highly recommended to use inline filtration on all lines supplying fuel to the fuel changeover valve.
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Installing a fuel valve with appropriate filtration
When installing a fuel valve, it is important to use appropriate filtration to prevent particulate matter such as rust from fuel tanks from building up and causing equipment failure. Inline filtration should be used on all lines supplying fuel to the fuel changeover valve.
To install a second fuel filter, first shut off the fuel valve at the tank. Cut the fuel hose at the mounting location and carefully drain the contents, or plug the hose openings by inserting bolts and sealing with hose clamps. For an outboard, install the flange (filter head) level and above the bilge, between the primer bulb and the engine. For outboard installations, if your boat is designed with an engine well, this might be the best location, to keep the filter easy to access, yet out of the way. For inboards, install the flange between the tank and the engine. Hoses should not have any kinks or tight turns.
It is recommended to add a 10-micron fuel filter/water separator upstream of the filter at the engine to help reduce contaminants that might load up the stock fuel filter. This is especially important for modern EFI (Electronic Fuel Injection) and DFI (Direct Fuel Injection) engines, which are more prone to problems when fuel quality decreases. The 10-micron filter will act as the primary filter, with the stock fuel filter at the engine working as a secondary filter.
When running twin tanks, a six-port valve capable of switching both engine supply and return lines is important to prevent tank overflow and contamination between the tanks. The tank selector valve is the key component in managing such a setup. It is recommended to use a sealed and waterproof valve, such as the Pollak 6-port valve, which is a trusted and reliable unit.
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Using a DPDT On-On switch to change valve positions
A DPDT On-On switch is used to change valve positions in a dual fuel tank system. DPDT stands for Dual Pole Dual Throw, meaning the switch has two sides that are electrically separate from each other. This type of switch is often dash-mounted and is used to control the fuel valve, which switches the supply and return lines for each tank.
The DPDT On-On switch has two positions, and each switch is called a pole, while each switch position is called a throw. In this case, the two throws are both "on" positions, with no centre "off" position. This allows the switch to control which tank is in use by toggling between the two poles, which are linked together so that both actions happen simultaneously.
One side of the DPDT switch is used to control the sending unit connected to the gauge, while the other side gives power to the fuel valve, determining which tank is in use. This is important for preventing tank overflows and contamination between the tanks, which is a key concern when running a dual fuel system.
When using a DPDT On-On switch to change valve positions, it is important to ensure that the switch is properly wired and that appropriate filtration is used on all lines supplying fuel to the fuel changeover valve. This will help prevent any particulate matter from building up and causing failures in the precise automotive equipment.
Overall, the DPDT On-On switch is a crucial component in a dual fuel tank system, allowing for the safe and effective switching between the two tanks.
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Monitoring fuel levels with a gauge in the aux tank
To monitor fuel levels in the aux tank with a gauge, it is necessary to have a gauge that reads the same resistance or voltage as the factory gauge. This allows for a seamless transition between tanks and ensures that the gauge accurately reflects the fuel level in the active tank. It is usually not difficult to find a compatible gauge, and this approach eliminates the need for manual priming of the engine in case of forgetting to switch tanks.
The fuel level sensor plays a crucial role in providing accurate fuel level readings. When installing a dual-fuel tank system, ensure that the switch solenoid switches not only the supply and return but also the signal from the fuel level sensor. This ensures that the gauge receives the correct signal and displays the fuel level in the aux tank accurately.
Additionally, consider installing a transfer pump with a timed switch. This setup allows you to run the main tank down to half capacity before activating the timed switch. The pump will then run for a set period, such as 10 minutes, before shutting off automatically. This automated process simplifies the management of dual fuel tanks and ensures a consistent fuel supply.
By incorporating a fuel level gauge, compatible resistance or voltage readings, and considering the fuel level sensor and transfer pump setup, you can effectively monitor fuel levels in your aux tank as part of your dual-fuel tank system. These measures enhance the reliability and efficiency of your vehicle's fuel system.
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Setting up transfer pumps for dual tanks
Setting up transfer pumps for dual fuel tanks is a complex process and is gaining popularity with 4WD users running long-range tanks. Here is a step-by-step guide on how to set up transfer pumps for dual fuel tanks:
Firstly, it is important to note that a six-port valve capable of switching both engine supply and return lines is essential. This prevents tank overflow and contamination between the tanks. The tank selector valve is the key component in managing this setup, with the Pollak 6-port valve being a trusted and reliable option.
Next, ensure that appropriate filtration is in place. Inline filtration should be used on all lines supplying fuel to the fuel changeover valve to prevent particulate matter buildup, which can cause failures.
When it comes to the transfer pump itself, a small electric pump is recommended. This allows you to shut it off in case of a leak, preventing a potential fire hazard. To control the transfer, you can use a timed switch, such as the one for a rear window defroster, which will run for a set time before shutting off automatically.
Additionally, consider using a fuel gauge that sums the fuel levels in both tanks and displays the total fuel onboard. This will help you monitor fuel levels and prevent running out of fuel.
Finally, remember to follow safety precautions and regulations. Do not pressurize the tank beyond the specified limit, and ensure that it is securely mounted. Contact your local authorities to understand any restrictions on the usage of such tanks.
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Frequently asked questions
The standard setup for dual fuel tanks involves a six-port valve that can switch both the engine supply and return lines between the two tanks. This prevents tank overflows and contamination between the tanks. It is important to use appropriate filtration when installing a fuel valve to prevent particulate matter buildup that can cause failures.
It is important to have a gauge in the auxiliary tank that reads the same resistance or voltage as the factory gauge to monitor fuel levels. Additionally, when using a transfer pump, a timed switch can be utilised to automatically shut off the pump when the main tank reaches half capacity.
The method of switching between tanks depends on the setup. Some systems use a switch solenoid that changes the supply, return, and signal from the fuel level sensor, allowing the gauge to show the level in the active tank. Other systems may utilise a transfer pump to move fuel from the secondary to the primary tank on demand.
Dual fuel tanks offer increased range and flexibility in fuel type. They are particularly advantageous for long-distance travel or areas with limited fuel accessibility. Additionally, dual fuel tanks can facilitate the use of alternative green fuels, such as biodiesel and vegetable oil conversions.
