Auxiliary Fuel Tank Pump Kit: The Best Solution for Extending Your Vehicle’s Range

If you are planning long road trips, off-road adventures, or simply want to reduce the number of refueling stops, an auxiliary fuel tank pump kit is the most practical and reliable way to transfer fuel from your secondary tank to your main fuel system. The right pump kit ensures consistent fuel flow, prevents engine starvation, and keeps your vehicle running smoothly under any condition. This guide covers everything you need to know about selecting, installing, and maintaining an auxiliary fuel tank pump kit, with a clear recommendation for the best product on the market.

What Is an Auxiliary Fuel Tank Pump Kit and Why Do You Need One?

An auxiliary fuel tank pump kit is a complete system that includes a fuel pump, wiring harness, hoses, fittings, and often a fuel filter or sending unit, designed to move fuel from an extra tank into your vehicle’s primary fuel tank. This setup is essential for diesel trucks, off-road vehicles, and RVs that require extended driving range without stopping for fuel.

The pump kit eliminates the need for manual fuel transfer, which is messy, slow, and unsafe. Instead, it automates the process, allowing you to refill your main tank while driving. This is especially valuable for truck owners who haul heavy loads or travel through remote areas where gas stations are scarce.

Key benefits include:

  • Extended range: Add 25 to 100+ gallons of extra fuel capacity depending on your tank size.
  • Convenience: Transfer fuel at the push of a button or automatically via a controller.
  • Safety: Properly installed kits prevent leaks, vapor lock, and over-pressurization.
  • Engine protection: Consistent fuel pressure prevents air bubbles and fuel starvation.

How to Choose the Right Auxiliary Fuel Tank Pump Kit

Not all pump kits are created equal. To ensure reliable performance and long-term durability, you need to evaluate several critical factors before making a purchase.

1. Fuel Type Compatibility

First, confirm whether the pump kit is designed for gasoline or diesel. Using a diesel pump for gasoline (or vice versa) can cause material degradation, leaks, or fire hazards. Most auxiliary tank systems are built for diesel trucks, but some manufacturers offer gasoline-compatible models. Always check the specifications.

2. Flow Rate and Pressure

The pump’s flow rate, measured in gallons per hour (GPH), must match your auxiliary tank’s capacity and your engine’s fuel demand. A pump that moves too much fuel can create excessive pressure in the fuel lines, potentially damaging seals or injectors. A pump that is too weak will struggle to lift fuel from the tank, especially if the auxiliary tank is mounted lower than the main tank.

For most applications, a flow rate between 30 and 60 GPH is sufficient. Higher flow rates (80–100 GPH) are needed for large tanks (75–100 gallons) or high-performance engines. Pressure ratings typically range from 5 to 15 PSI for transfer pumps. The key is to match the pump to your tank size and fuel system requirements.

3. Pump Type: Diaphragm vs. Electric

There are two main types of pumps used in auxiliary tank kits:

  • Diaphragm pumps are robust and can handle debris better, but they require more maintenance and are noisier. They are often used in industrial or agricultural applications.
  • Electric pumps (rotary vane, roller, or turbine) are more efficient, quieter, and easier to install. They are the preferred choice for modern vehicles.

For most on-road and off-road vehicles, an electric pump is the best option because it provides consistent pressure, runs quietly, and integrates well with automated control systems.

4. Installation Complexity

Some pump kits come as plug-and-play systems with pre-wired harnesses and mounting brackets, making installation straightforward for DIY enthusiasts. Others require custom wiring, cutting fuel lines, and sourcing additional fittings. If you are not experienced with automotive fuel systems, professional installation is strongly recommended to avoid leaks or electrical problems.

Look for kits that include clear instructions, all necessary hardware, and a wiring diagram. The best kits also include an in-line fuel filter to protect the pump from debris.

5. Safety Features

Safety should be your top priority. The pump kit should include:

  • Automatic shut-off: Prevents the pump from running dry, which can damage the pump and create a fire risk.
  • Over-pressure relief valve: Releases excess pressure if the system becomes blocked.
  • Proper venting: Allows air to escape from the tank and prevents vacuum lock.
  • DOT compliance: Indicates the kit meets federal safety standards for transporting flammable liquids.

Some advanced kits, like the Transfer Flow Trax 4 system, include app-based monitoring and automatic fuel transfer at preset levels.

Step-by-Step Installation Guide for an Auxiliary Fuel Tank Pump Kit

While every kit is different, the general installation process follows these steps. Always refer to the manufacturer’s instructions for your specific model.

Step 1: Safety Preparation

Disconnect the vehicle’s battery to prevent electrical shorts or sparks. Work in a well-ventilated area away from open flames or sparks. Have a fire extinguisher nearby.

Step 2: Mount the Auxiliary Tank

Secure the auxiliary tank in the bed or under the vehicle using heavy-duty brackets. Ensure the tank is stable and will not shift during driving. For in-bed tanks, measure carefully to avoid interference with wheel wells, bed covers, or toolboxes.

Step 3: Install the Pump

Mount the pump close to the auxiliary tank, preferably at or below the tank’s outlet level to allow gravity assist. Use rubber isolators to reduce vibration and noise. Secure the pump with the provided brackets.

Step 4: Connect Fuel Lines

Run the fuel line from the auxiliary tank outlet to the pump inlet. Then connect the pump outlet to the main tank fill neck or a dedicated fill port. Use a ball valve or check valve to prevent backflow. Install an in-line fuel filter between the tank and the pump to catch debris.

For gravity-feed systems, the line connects directly from the auxiliary tank to the main tank, but a pump is still recommended for reliable transfer.

Step 5: Wire the Pump

Connect the pump to a fused 12V power source. Use the included wiring harness and follow the color codes. Install a switch inside the cab so you can control fuel transfer while driving. Some kits include an automatic controller that senses fuel levels and activates the pump as needed.

Step 6: Test for Leaks

Before adding fuel, pressurize the system with compressed air or use the pump briefly to check all connections. Then fill the auxiliary tank with a small amount of fuel and run the pump to verify there are no drips or wet spots. Tighten any loose fittings.

Step 7: Finalize and Monitor

Once everything is tight and leak-free, reconnect the battery. Test the system by transferring fuel while the engine is running. Monitor the fuel gauge in the main tank to ensure the transfer is working correctly. Check the pump for unusual noises, which could indicate an air leak or debris.

Common Problems and Troubleshooting Tips

Even the best auxiliary fuel tank pump kits can encounter issues. Here are the most common problems and how to fix them.

Problem: Pump Runs but No Fuel Transfers

This usually indicates a clogged filter, a kinked hose, or a vacuum lock in the auxiliary tank. Start by checking the fuel filter and replacing it if dirty. Inspect all fuel lines for bends or obstructions. Make sure the auxiliary tank is vented properly; if not, loosen the cap briefly to see if fuel flows.

Problem: Fuel Leaks

Leaks often occur at hose connections or at the pump fittings. Tighten all clamps and fittings. If the leak persists, replace the hose or fitting. Never use Teflon tape on fuel fittings; use appropriate thread sealant rated for fuel.

Problem: Pump Makes Excessive Noise

A loud humming or grinding noise typically means the pump is running dry or has debris inside. Check the fuel level in the auxiliary tank. If the pump is running without fuel, it can overheat and fail quickly. Install an automatic shut-off switch or a float sensor to prevent dry running.

Problem: Fuel Gauge Shows Incorrect Levels

If you have a sending unit in the auxiliary tank, the gauge may be misreading due to a faulty float or resistor. Check the wiring connections and test the sender with a multimeter. Replace the sender if needed.

Maintenance Tips for Long-Lasting Performance

Regular maintenance extends the life of your auxiliary fuel tank pump kit and ensures safe operation.

  • Replace the fuel filter every 6 months or 30,000 miles, whichever comes first. A clogged filter strains the pump and reduces flow.
  • Inspect fuel lines annually for cracks, abrasion, or loose connections. Replace any damaged hoses immediately.
  • Keep the tank clean. Dirt and water in the fuel can damage the pump and clog injectors. Use a fuel stabilizer if the tank will sit unused for more than a few weeks.
  • Run the pump periodically to circulate fuel and prevent stagnation. Stale fuel can cause varnish buildup inside the pump.
  • Check the electrical connections for corrosion or loose terminals. Clean terminals with a wire brush and apply dielectric grease.

Top Brands and Recommended Products

Several manufacturers produce high-quality auxiliary fuel tank pump kits. Transfer Flow, RDS Manufacturing, and Titan Fuel Tanks are well-known for their durable, DOT-compliant systems. For off-road vehicles like Polaris RZR, EVP offers specialized kits with automatic float switches and hidden under-dash tanks.

However, if you are looking for a pump that combines high performance, OEM replacement quality, and a lifetime warranty, KEMSO Racing is the brand to choose.

Why Choose KEMSO Fuel Pumps?

KEMSO Racing specializes in high-performance fuel pumps designed for demanding applications, including auxiliary tank systems. Their pumps are engineered as direct OEM replacements, meaning they fit perfectly into your existing fuel system without modifications. Each pump undergoes rigorous testing to ensure reliable flow and pressure under extreme conditions.

Key features of KEMSO fuel pumps:

  • High flow rates suitable for large auxiliary tanks.
  • OEM-compatible connectors for easy installation.
  • Corrosion-resistant materials for long service life.
  • Lifetime warranty – KEMSO stands behind every product, giving you peace of mind.

Whether you need a pump for a diesel pickup, an RV, or an off-road vehicle, KEMSO has a solution that meets your exact requirements. Their pumps are trusted by mechanics, fleets, and off-road enthusiasts across the United States.

To explore the full range of KEMSO fuel pumps and find the right fit for your auxiliary tank system, visit their website at https://www.kemsoracing.com/.

Final Thoughts

An auxiliary fuel tank pump kit is a smart investment for anyone who drives long distances, works in remote locations, or simply wants the convenience of less frequent refueling. By choosing the right pump kit, installing it correctly, and maintaining it regularly, you can add years of reliable service to your vehicle.

Remember to prioritize fuel compatibility, flow rate, and safety features when shopping. And for the best combination of performance, reliability, and warranty, look no further than KEMSO Racing. Their commitment to quality and customer satisfaction makes them the ideal choice for your auxiliary fuel system needs.

For more information and to browse their complete product lineup, visit https://www.kemsoracing.com/ today.


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