Mercedes Mullins
Wiring a factory second fuel tank can be a complex process, and it is important to understand the basics before attempting any such installation. The wiring of a second fuel tank can vary depending on the make and model of the vehicle, with sources citing wiring diagrams and colour codes for Ford, Chevrolet, GMC, and GM trucks. The wires are connected to the fuel gauge, with some wires running to the tanks, and others to the selector valve. It is important to understand the function of each wire, as well as the potential issues that may arise, such as fuel gauge problems or short circuits.
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What You'll Learn
Wiring colours and their functions
The wiring colours and their functions for a factory second fuel tank can vary depending on the vehicle's make, model, and year. Here is a detailed guide based on the information found:
For a 1970 F-250 Ford truck, the auxiliary fuel tank switch has six wires: two green wires, one orange wire, and three black wires. The green wires are believed to run to the fuel gauge, and the orange wire is likely the power wire (+). The black wires may be grounds, but their specific function is unclear and may require further investigation or a wiring diagram.
For a GM Square Body truck from 1973 to 1987, the fuel tank sender wire is typically tan or pink. The pink wire is connected to the fuel gauge sending unit, accommodating the factory tachometer clusters. The tan wire is associated with earlier models, while the change to pink occurred around 1978.
In a separate discussion, a user with a stand-alone LS3 crate engine harness inquires about fuel pump wiring. They mention a grey wire that goes to the 12V power wire from the harness, a large black wire to the ground, a blue wire for the level sensor, and a smaller black wire for the sensor ground. On the driver's side tank, there is a pressure sensor with grey, green, and black wires. The passenger side tank, which houses the fuel pump, has an additional set of wires: blue, black, and black with a white stripe, which are believed to be for the fuel level sensor and transfer pump.
It is important to note that wiring colours and functions can vary across different vehicle models and years. Always refer to the specific wiring diagrams, manuals, or expert advice for your vehicle before attempting any electrical work.
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Fuel gauge issues and solutions
Fuel gauge issues can be caused by a variety of factors, including a bad gauge, a bad sending unit, a broken wire or ground, or a failing circuit board. To diagnose the issue, you can perform the following steps:
- Check the fuel gauge terminals: Attached to the back of the fuel gauge are three male terminals at 3, 6, and 9 o'clock. Run a ground wire to the 6 o'clock terminal and a power wire to the 9 o'clock terminal. If the needle moves past the full mark, the gauge is functioning correctly.
- Verify the sending unit: The factory sending unit power wire is typically orange or tan and runs inside the frame. You can confirm the ground wire, which is usually purple or black, with a test lead. Use a multimeter to verify that the sending unit is working correctly. The resistance should be 0 ohms when empty and 90 ohms when full.
- Inspect wire connections: Ensure that all wires are connected securely and that there are no broken or damaged wires. Look for any signs of burning or discolouration, which could indicate a direct short or other electrical issues.
- Refer to wiring diagrams: Consult vehicle-specific wiring diagrams or forums for your particular make and model to understand the correct wire colours and connections. For example, older Chevrolet models used a TAN wire for the fuel tank sender wire, while later models switched to a PINK wire.
- Test fuel level sensors: If you have a stand-alone engine harness, you may need to combine the fuel level sensor wires for the fuel gauge, as suggested in some vehicle manuals.
To solve fuel gauge issues, you can try the following:
- Replace the fuel gauge: If the gauge is faulty, replace it with a new one and ensure proper wiring connections.
- Repair or replace the sending unit: If the sending unit is faulty, repair or replace it, ensuring that the wires are connected correctly according to the wiring diagram for your vehicle.
- Fix broken wires: If there are broken or damaged wires, repair or replace them, ensuring proper connections and insulation.
- Check for ground issues: Verify that the ground wires are connected correctly and are not loose or damaged.
- Calibrate the fuel gauge: Perform a full/empty calibration to ensure that the fuel gauge is accurately reflecting the fuel level.
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Electric switch for main and auxiliary tanks
If you have a vehicle with one main and one auxiliary fuel tank, you can use a dual tank switching valve selector to control which tank is being used. This will allow you to run two separate fuel tanks and draw from only one at a time.
The dual tank switching valve selector has three ports: two inlets and one outlet. You can run a fuel line from each tank to the valve and a line from the valve to your engine. The selector valve can be switched using a common toggle or rocker switch.
There are a variety of dual tank switching valve selectors available for purchase, such as the FV1/FV1T Fuel Selector Valve Kit, which comes with three stainless steel hose clamps, 12' 10GA wire, an inline fuse and fuse holder, butt and eyelet connectors. This kit is designed for vehicles with one main and one auxiliary tank and works with 12-volt systems. It is important to note that this kit is not suitable for vehicles with fuel return lines or marine use.
Other options for dual tank switching valve selectors include the JDMSPEED 6 Port Fuel Tank Selector Valve, which is compatible with Ford F250 F350 Super Duty vehicles, and the ACDelco Switch Fuel Tank Selector D7089C, which is designed for standard cab pickup trucks.
When purchasing a dual tank switching valve selector, it is important to ensure that it is compatible with your vehicle's fuel system and that you follow the manufacturer's instructions for proper installation and use.
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Wiring diagrams for different models
For example, for a 1977 Scottsdale with dual tanks, one source details how there is a wire disconnected at the selector valve underneath the truck. The solution to this issue is to dig up the wiring diagram for this model.
Another source provides a step-by-step process for wiring a factory second fuel tank in a GM Square Body model from 1973-1987. It explains that the PNK-30 wire usually runs from the cluster to the bulkhead, and then from the bulkhead to the sender unit on the tank. If it is a dual-tank model, it runs to the selector valve, and then to the tanks as PNK/WHT and PNK/BLK wires.
A user on a forum for Ford vehicles details their process of wiring a second fuel tank in their 1987 F250 Ford Diesel 6.9. They explain that the wiring diagram for the FUEL TANK SELECTOR VALVE (FTSV) can be found on the Ford Truck Enthusiasts Forums.
A different user on a boat forum provides a wiring diagram for dual tanks, which includes a picture of their setup, and explains that they have kept the +12volts separate from the signal and ground.
Additionally, a user on a GM Square Body forum provides a layman's guide to fuel gauge wiring. They explain that the three male terminals attached to the back of the fuel gauge at 3, 6, and 9 o'clock should be wired correctly to confirm that the gauge is good.
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Fuel pump wiring
Firstly, it is important to identify the wires and their respective functions. The fuel pump wiring typically includes power wires, ground wires, and sensor wires. Power wires are usually colour-coded and provide electricity to the fuel pump. Ground wires ensure a safe path for electrical current and are often black or purple. Sensor wires, such as the level sensor and pressure sensor wires, provide data to the vehicle's computer for efficient fuel management.
When wiring a factory second fuel tank, it is essential to determine the type of fuel pump being used. In some cases, the original tank may have a mechanical switch, while the new tank has an electric fuel pump. This electric pump requires wiring into the switch to function correctly. Additionally, the wiring diagram and colour-coding may vary depending on the make and model of your vehicle. For example, a Toyota Tacoma may have different wiring requirements compared to a Ford F-250.
To wire the fuel pump, you will need to connect the power wire from the fuel pump relay to the fuel pump itself. This power wire is typically 12V and can be identified by its colour, such as grey or orange. The ground wire, usually black, should also be connected to the fuel pump to ensure a safe electrical path. Additionally, any sensor wires, such as the level sensor and pressure sensor wires, should be properly connected to their respective sensors and the vehicle's computer.
It is important to note that the wiring process may vary depending on the specific configuration of your vehicle and fuel tank setup. Always refer to the vehicle's manual or seek professional assistance if you are unsure about any part of the wiring process. Additionally, it is crucial to exercise caution when working with electrical systems to prevent short circuits or other potential hazards.
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Frequently asked questions
It depends on the make and model of your vehicle. For a 1970 F-250, you can wire the switch to send power to the main or auxiliary tank. If you have a stand-alone LS3 crate engine harness, the 12v power wire goes to the fuel pump.
The colours of the wires vary depending on the make and model of your vehicle. For a 1970 F-250, there are two green wires, one orange wire, and three black wires. For a GM Square Body (1973-1987), the wire is tan with a white stripe.
The process will vary depending on the specific vehicle and setup. It is recommended to consult a professional or a mechanic to ensure the wiring is done correctly and safely.
Yes, it is important to ensure that the wiring is done correctly to avoid issues such as short circuits or incorrect fuel gauge readings. It is also important to consider the fuel pump setup and whether it needs to be wired into the switch.
Yes, it is possible to use an electric switch to select between the main and auxiliary tanks. However, it is important to ensure that the wiring is done correctly and that the switch is compatible with your vehicle's electrical system.
