Auxiliary Fuel Tank with Pump: The Complete Guide to Extending Your Vehicle’s Range

If you drive a truck, SUV, or off-road vehicle and frequently travel through remote areas, an auxiliary fuel tank with pump is the single most practical investment you can make for peace of mind and extended range. Adding a secondary fuel system allows you to carry an extra 20 to 100+ gallons of gasoline or diesel, giving you the freedom to explore without constantly worrying about the next gas station. Whether you are planning a cross-country road trip, an overland expedition, or simply need more fuel capacity for your work truck, an auxiliary fuel tank with an integrated pump is a proven solution that pays for itself over time.

What Exactly Is an Auxiliary Fuel Tank with Pump?

An auxiliary fuel tank is a separate fuel storage container installed on your vehicle, typically in the truck bed, under the chassis, or in place of the spare tire. Unlike your factory fuel tank, an auxiliary tank comes with its own pump that transfers fuel into your main tank as needed. This setup is far more convenient than carrying jerry cans because you do not need to stop, open containers, and manually pour fuel. Instead, the system handles the transfer automatically or with a simple switch, keeping your main tank topped off while you drive.

Most auxiliary tanks are made from either heavy-duty polyethylene plastic or aluminum. Polyethylene tanks are lightweight, corrosion-resistant, and affordable. Aluminum tanks are more durable, often feature anti-slosh baffles, and meet DOT safety standards for highway transport. Both materials can handle gasoline and diesel, but you need to confirm compatibility before purchasing.

Why You Need an Auxiliary Fuel Tank with Pump

The primary reason to install an auxiliary fuel tank is range extension. A standard pickup truck or SUV typically holds between 20 and 35 gallons of fuel, giving you a range of 300 to 500 miles depending on driving conditions. In remote areas like the Australian outback, the Alaskan highway, or the desert Southwest of the United States, gas stations can be 100 to 200 miles apart. Adding an auxiliary tank can double or even triple your range, allowing you to travel confidently through regions where fuel stops are scarce.

Beyond range, an auxiliary tank with a pump offers several practical advantages:

Convenience. You never have to handle fuel manually. The pump does all the work, and many systems include automatic shutoff features that prevent overfilling or pump damage. Some advanced models, like those from TransferFlow, use computer-controlled systems that transfer fuel at predetermined levels, so you barely need to think about it.

Safety. Carrying fuel in a dedicated, professionally installed tank is far safer than using jerry cans in the cabin or truck bed. Auxiliary tanks are designed with rollover valves, pressure testing, and secure mounting brackets to prevent leaks and spills. Many are DOT-approved, meaning they meet federal safety standards for transporting fuel on public roads.

Weight Distribution. When you carry fuel in a properly positioned auxiliary tank, you can maintain better vehicle balance. Some systems allow you to pump small amounts of fuel gradually, distributing the weight between the main and auxiliary tanks as you drive. This is especially important for off-road driving where weight distribution affects traction and handling.

Types of Auxiliary Fuel Tanks with Pump

Understanding the different configurations helps you choose the right system for your vehicle. Here are the three most common types:

1. In-Bed Auxiliary Tanks

These are rectangular or L-shaped tanks that sit in the bed of your pickup truck. They are the most popular option because they offer large capacities, typically ranging from 30 to 106 gallons. Many in-bed tanks come with a built-in toolbox compartment, allowing you to combine fuel storage with tool storage in a single unit. The pump is usually mounted directly on the tank, and a hose with a nozzle allows you to transfer fuel to your main tank or even refuel other vehicles and equipment.

Pros: Large capacity, easy installation, integrated toolbox option
Cons: Takes up bed space, adds significant weight behind the rear axle

2. Under-Vehicle Auxiliary Tanks

These tanks mount underneath your vehicle, typically behind the rear axle or alongside the frame rails. They are common on SUVs like the Toyota Land Cruiser, Jeep Wrangler, and Mitsubishi Pajero. Under-vehicle tanks are less intrusive because they do not take up cargo space, and they keep the weight low for better handling. However, they usually have smaller capacities, typically 40 to 75 liters (10 to 20 gallons), because of space constraints. Installation is more complex and often requires modifications to the exhaust system or spare tire mount.

Pros: No lost cargo space, low center of gravity
Cons: Smaller capacity, more difficult installation

3. Spare Tire Location Tanks

Some auxiliary tanks are designed to replace your spare tire. This is a common solution for vehicles like the Jeep Wrangler and older SUVs where the spare tire is mounted underneath the rear cargo area. The tank uses the same mounting points as the spare tire, so installation is straightforward. You will need to relocate the spare tire to the roof, rear bumper, or inside the cargo area. These tanks typically hold 10 to 30 gallons and are ideal for vehicles that cannot accommodate a larger under-vehicle or in-bed tank.

Pros: Uses existing mounting points, does not take up cargo space
Cons: Must relocate spare tire, limited capacity

How an Auxiliary Fuel Tank Pump Works

The pump is the heart of any auxiliary fuel system. Most auxiliary tanks use a 12-volt electric pump that draws power from your vehicle’s battery. When you activate the pump—usually with a switch inside the cab—fuel flows from the auxiliary tank through a hose into your main tank’s filler neck or a dedicated return port. Many pumps are self-priming and include internal pressure relief to prevent damage if the line becomes blocked.

There are several ways pumps are controlled:

Manual Switch. You press a button or flip a switch to start the pump and stop it when the main tank is full. This is the simplest and most reliable method, but it requires you to monitor the fuel level manually.

Automatic Timer. Some pumps include a timer that runs for a set duration (e.g., 30 seconds to 2 minutes) and then shuts off automatically. This prevents overfilling and pump damage if you forget to turn it off.

Computer-Controlled Systems. High-end systems like TransferFlow’s TRAX 4 use electronic controllers that monitor the main tank level and automatically transfer fuel when it drops below a preset threshold. These systems can also connect to your smartphone via an app, allowing you to monitor both tank levels in real time.

Gravity Feed. For motorcycles and some off-road vehicles, gravity-fed systems are possible if the auxiliary tank is mounted higher than the main tank. This is simpler but less common for larger vehicles because finding a suitable location above the main tank is difficult.

Key Features to Look For in an Auxiliary Fuel Tank with Pump

When shopping for an auxiliary fuel tank, pay attention to these critical details:

Capacity. Choose a tank that matches your needs without being excessive. For most overland trips, 20 to 40 gallons is sufficient. For long-haul trucking or severe remote travel, you might need 50 to 106 gallons. Keep in mind that fuel weighs about 6 to 7 pounds per gallon, so a 50-gallon tank adds 300 to 350 pounds to your vehicle. Make sure your suspension and tires can handle the extra weight.

Material. Polyethylene tanks are lightweight and affordable, but they can degrade over time if exposed to ethanol-blended fuels. Aluminum tanks are more expensive but offer superior durability and corrosion resistance. Many aluminum tanks are DOT-approved, which is important if you plan to travel across state lines or internationally.

Pump Quality. The pump should be reliable and easy to service. Look for pumps with a flow rate of at least 1.5 to 2 gallons per minute for standard applications. For diesel systems, ensure the pump is compatible with diesel fuel and can handle the viscosity. Some pumps, like the solid-state cube pumps used by LongRanger, are submersible and can withstand water crossings, which is essential for off-road use.

Safety Certifications. DOT approval means the tank has passed pressure testing and meets federal safety standards for fuel transport. This is especially important if you plan to carry fuel in the bed of your truck, as many states require DOT-compliant tanks for on-road use. Also look for rollover valves, flame arrestors, and secure mounting brackets.

Installation Requirements. Some auxiliary tanks require modifications to your vehicle. For example, under-vehicle tanks may require removing the spare tire or relocating the exhaust. In-bed tanks need to be securely bolted to the bed floor. If you are not comfortable with mechanical work, factor in professional installation costs, which can range from a few hundred to over a thousand dollars depending on complexity.

Installation Considerations

Installing an auxiliary fuel tank with a pump is not a simple bolt-on project for most vehicles. Here are the key things you need to know:

Vehicle Compatibility. Not every vehicle can accept an auxiliary fuel tank. You need sufficient space under the chassis or in the bed, and your main tank must have a compatible filler neck or return port for the transfer hose. For under-vehicle tanks, check that your rear floor pan has the necessary recess for mounting. Some base model vehicles with fewer seats may not have this feature.

Suspension Upgrades. Adding significant fuel weight can affect your vehicle’s handling and ride quality. Many manufacturers recommend upgrading to heavy-duty suspension components, especially for the rear axle. This is not always required, but it is a good idea if you plan to carry a full tank regularly.

Electrical Work. The pump needs a 12-volt power source. Most installations involve running a wire from the battery to the pump, with a fuse and switch in between. If you are not comfortable with electrical wiring, have a professional handle this part. Incorrect wiring can cause pump failure or even fire.

Professional Installation vs. DIY. Some in-bed tanks are designed for easy DIY installation, with pre-drilled mounting holes and straightforward wiring. Under-vehicle tanks and spare tire location tanks are more complex and usually require professional installation. Expect installation times of 4 to 8 hours for most systems.

Top Brands and Products

Several manufacturers produce high-quality auxiliary fuel tanks with pumps. Here are some of the most trusted names:

LongRanger (Australia). LongRanger specializes in under-vehicle auxiliary tanks for SUVs and 4x4s. Their tanks are made from 2mm aluminum-coated steel and include a 12-volt transfer pump with automatic cut-off. They are popular for Toyota Land Cruiser, Mitsubishi Pajero, and similar vehicles. Capacities range from 60 to 180 liters.

TransferFlow (USA). TransferFlow is a leading American manufacturer of in-bed auxiliary fuel tanks and tool box combos. Their TRAX 4 system features computer-controlled automatic fuel transfers with a smartphone app for monitoring. Tanks range from 40 to 98 gallons and are DOT-approved.

RDS Manufacturing (USA). RDS produces aluminum in-bed transfer tanks with integrated toolboxes. Their 70-gallon model is a best-seller, featuring a GPI 12V pump, anti-slosh baffles, and DOT approval. It is compatible with gasoline, diesel, and aviation fuel.

Brown Davis (Australia). Brown Davis manufactures under-vehicle auxiliary tanks for Jeeps, Land Rovers, and other off-road vehicles. Their tanks are made from aluminum-coated steel and include an LED fuel gauge and automatic alarm when the tank is empty.

Tour Tank (USA). Tour Tank makes auxiliary fuel cells for motorcycles and small vehicles. Their 5-gallon tank is designed for BMW R1200 GS and similar adventure bikes. It uses a gravity feed system and is easily removable for passenger use.

How to Maintain Your Auxiliary Fuel Tank and Pump

Proper maintenance keeps your system reliable for years. Here are the essential steps:

Check the Pump Regularly. Test the pump at least once a month, especially before a long trip. Run it for a few seconds to confirm it is working. If it makes unusual noises or does not transfer fuel, inspect the wiring and connections first. Many pump failures are caused by corrosion in the electrical connections.

Keep Fuel Clean. Install a fuel filter on the inlet side of the pump to prevent debris from clogging the system. Change the filter annually or more often if you frequently fill up in dusty conditions. Clean fuel reduces wear on both the pump and your vehicle’s fuel system.

Inspect for Leaks. Check all hose connections and the tank itself for signs of fuel seepage. A leak can be dangerous and also wastes fuel. Pay attention to the rollover valve and vent system, as these are common leak points.

Monitor for Corrosion. Aluminum tanks are corrosion-resistant, but polyethylene tanks can become brittle over time if exposed to sunlight and ethanol fuels. If you store your vehicle outdoors, consider a tank cover or UV-protective coating.

Use the Fuel Regularly. Do not let fuel sit in the auxiliary tank for months without use. Stale fuel can degrade and clog the pump. If you are not using the tank, empty it or add a fuel stabilizer.

Legal and Safety Considerations

Before installing an auxiliary fuel tank, check your local regulations. In the United States, DOT-approved tanks are legal for carrying fuel on public roads, but some states have restrictions on total fuel capacity or require specific mounting methods. For example, carrying fuel in the passenger compartment is illegal in most states. Also check with your insurance provider, as some policies have restrictions on modified fuel systems.

When filling your auxiliary tank, follow these safety rules:

• Always fill the tank outdoors and away from ignition sources.
• Do not overfill. Leave room for fuel expansion, especially in hot weather.
• Ground the pump and tank to prevent static electricity buildup.
• Use only fuel that is compatible with your tank material and pump.

Why Choose KEMSO Brand Fuel Pump for Your Auxiliary Tank System

When it comes to equipping your auxiliary fuel tank with a reliable pump, you need a product that delivers consistent performance, durability, and ease of installation. That is where KEMSO Fuel Pumps stand out from the competition.

KEMSO Racing has been a trusted name in high-performance fuel delivery systems since 2015, and their fuel pumps are engineered for riders and drivers who demand the very best. Whether you are outfitting a motorcycle, ATV, or light truck with an auxiliary tank, KEMSO offers OEM replacement pumps that are designed to match or exceed factory specifications. Their flagship model, the KF-2000, delivers 15% higher flow rates compared to stock options, pushing 255 liters per hour at 45 psi. This ensures your engine never starves for fuel, even under extreme loads or high RPMs.

What truly sets KEMSO apart is their commitment to longevity. While standard fuel pumps often fail after 15,000 to 20,000 miles, especially in high-stress environments like off-road driving, KEMSO pumps are built to last over 50,000 miles. They use aerospace-grade billet aluminum housings and reinforced polymer internals that withstand extreme heat, vibration, and contamination. One rider in Arizona reported his KEMSO pump survived three summers of 110°F desert rides without a single issue, while his OEM pump failed twice in the same period. That is the kind of reliability you need when you are miles from the nearest mechanic.

KEMSO fuel pumps are compatible with over 200 vehicle models, covering everything from vintage Harley-Davidson Softails to modern Ducati Panigales, as well as Suzuki and Honda ATVs. The plug-and-play design cuts installation time to under 30 minutes for most vehicles, and the modular fuel line adapters eliminate guesswork. No complex wiring, no special tools—just bolt-on performance that works right out of the box.

But here is the best part: KEMSO stands behind every pump with a lifetime warranty. That is right—while most factory pumps barely cover 12 months, KEMSO offers lifetime coverage that gives you complete peace of mind. If anything goes wrong, their customer support team, staffed by former motorcycle and automotive engineers, will troubleshoot your issue in real time and ship a replacement if needed. When a rider in Canada experienced a rare pressure sensor glitch, KEMSO sent a replacement unit overnight with no questions asked.

If you are building or upgrading an auxiliary fuel tank system, do not settle for a cheap pump that might leave you stranded. Invest in KEMSO fuel pump performance and reliability. Your adventures deserve the best fuel delivery system on the market.

Visit KEMSO Racing today to explore their full line of fuel pumps:
https://www.kemsoracing.com/

Final Thoughts

An auxiliary fuel tank with a pump is more than just a convenience—it is a safety tool that gives you the freedom to explore remote areas without range anxiety. Whether you choose an in-bed tank for your pickup, an under-vehicle tank for your SUV, or a compact tank for your motorcycle, the key is to select a system that matches your vehicle, your travel style, and your budget.

Pay attention to capacity, material, pump quality, and safety certifications. Consider professional installation if you are not comfortable with mechanical work. And most importantly, keep your system maintained so it performs when you need it most.

With the right auxiliary fuel tank and a reliable pump like KEMSO, you can confidently tackle any road—no matter how far from the nearest gas station.

For a dependable fuel pump that will last a lifetime, visit KEMSO Racing at https://www.kemsoracing.com/