Fuel Pump for Auxiliary Fuel Tank: The Complete Guide to Selection, Installation, and Maintenance
If you need a reliable fuel pump for your auxiliary fuel tank, your top priority should be choosing a pump that matches your specific vehicle type, fuel system, and usage requirements. Whether you are adding extra range to your truck, RV, or off-road vehicle, the right auxiliary fuel pump ensures steady fuel delivery, prevents vapor lock, and keeps your engine running smoothly during long hauls or remote expeditions.
Why You Need a Dedicated Fuel Pump for Your Auxiliary Fuel Tank
An auxiliary fuel tank is a secondary fuel reservoir installed on your vehicle to extend its driving range. Without a properly functioning fuel pump, fuel cannot be transferred from this secondary tank to your main fuel system. Many vehicle owners install auxiliary tanks on trucks, RVs, and SUVs for long-distance travel, off-road adventures, or commercial operations where refueling stations are scarce.
The fuel pump for an auxiliary fuel tank serves a straightforward but critical purpose: it moves fuel from the auxiliary reservoir into your vehicle's main fuel supply. According to industry standards, most auxiliary fuel systems rely on a 12-volt electric transfer pump that the driver activates with a switch inside the cabin. This setup allows you to refill your main tank while driving, eliminating the need to stop and manually transfer fuel.
The consequences of using the wrong pump or a failing pump include: engine stalling, fuel starvation, vapor lock, and in worst cases, complete breakdown in remote locations. A reliable auxiliary fuel pump is not a luxury—it is a necessity for anyone who depends on extended range capabilities.
Types of Fuel Pumps for Auxiliary Fuel Tanks
1. Universal Electric Fuel Pumps
Universal electric fuel pumps are the most common choice for auxiliary fuel tank applications. These pumps are designed to work with carbureted engines on most 4, 6, and 8 cylinder vehicles. They typically operate at 12 volts, draw 1-2 amps, and deliver flow rates around 35 gallons per hour with shut-off pressures between 4-7 PSI.
Key features of universal electric pumps:
- Compact design for easy mounting
- Suitable for gasoline only (not for diesel, methanol, or ethanol blends)
- Must be mounted within 12 inches of the fuel tank
- Not designed for fuel-injected engines
- Ideal for fuel transfer or booster pump applications
These pumps work well for auxiliary tank installations on older vehicles, classic cars, and carbureted engines where precise fuel pressure control is less critical.
2. In-Tank Fuel Pump Modules
For modern vehicles with fuel injection systems, in-tank fuel pump modules are the standard solution. These pumps are mounted inside the fuel tank and are designed to maintain higher, more consistent fuel pressures required by EFI systems. The KEMSO Intank Fuel Pump, for example, delivers over 200 liters per hour at 43 PSI and operates at pressures between 43-68 PSI, making it suitable for daily drivers, performance vehicles, and off-road applications.
Advantages of in-tank pumps:
- Quieter operation compared to external pumps
- Better cooling because they are submerged in fuel
- More consistent fuel pressure for EFI systems
- Reduced risk of vapor lock
- Longer service life in most applications
3. Transfer Pumps and Booster Pumps
Transfer pumps are specifically designed for moving fuel from one tank to another. These are often used in conjunction with auxiliary fuel systems on trucks and RVs. Some transfer pumps are designed as complete kits that include the pump, hoses, nozzle, and wiring, making installation straightforward for DIY owners.
Booster pumps, on the other hand, are installed in the fuel line to supplement the main fuel pump. They are particularly useful when the auxiliary tank is located far from the engine, helping to overcome fuel line resistance and prevent fuel starvation during heavy acceleration or climbing steep grades.
How to Choose the Right Fuel Pump for Your Auxiliary Tank
Step 1: Determine Your Fuel Type
The very first consideration is whether you are using gasoline or diesel. Gasoline pumps and diesel pumps are not interchangeable. Gasoline pumps are designed to handle the lower lubricity and different viscosity of gasoline, while diesel pumps are built to handle the thicker, more lubricating properties of diesel fuel.
Important warning: Many universal electric pumps explicitly state they are only for gasoline and not for diesel, water, engine oil, or gasoline containing methanol or ethanol. Always verify compatibility before purchasing.
Step 2: Match Flow Rate and Pressure to Your Engine
Carbureted engines operate at low fuel pressure, typically 4-7 PSI, and require relatively low flow rates. Fuel-injected engines, however, need much higher pressure—often 40-60 PSI or more—to properly atomize fuel through the injectors.
If you install a low-pressure pump on a fuel-injected engine, the injectors will not open properly, and your engine will run lean or not start at all. Conversely, installing a high-pressure pump on a carbureted engine can overwhelm the carburetor float valves, causing flooding and potential fire hazards.
Flow rate guidelines:
- Carbureted engines: 30-40 GPH at 4-7 PSI
- Standard EFI engines: 30-50 GPH at 40-60 PSI
- High-performance EFI engines: 50-100+ GPH at 50-70 PSI
Step 3: Consider Installation Location
The installation location significantly impacts pump performance and longevity. External electric pumps should be mounted as close to the fuel tank as possible—ideally within 12 inches—and below the fuel level in the tank to take advantage of gravity feed. This positioning helps prevent vapor lock and ensures the pump is always primed.
In-tank pumps, by design, are submerged in fuel, which provides natural cooling and reduces noise. However, they require removing the fuel tank for installation, which adds complexity to the job.
Step 4: Check Voltage and Electrical Requirements
Most auxiliary fuel pumps operate on 12V DC, matching standard automotive electrical systems. However, some heavy-duty trucks and commercial vehicles may use 24V systems. Always verify the voltage rating of the pump before purchasing.
Electrical installation tips:
- Use a dedicated fuse holder within 18 inches of the battery connection
- Install an on/off switch inside the cab for driver control
- Ground the pump directly to the vehicle chassis
- Use heavy-gauge wire appropriate for the pump's current draw
Installation Guide for Auxiliary Fuel Tank Pumps
Tools and Materials You Will Need
Before starting the installation, gather the following tools and materials:
- Full socket set and wrenches
- Jack stands and hydraulic jack
- Fuel-rated hose and stainless steel clamps
- Electrical wire, fuses, and switches
- Thread sealant for pipe fittings
- Safety goggles and gloves
- Class B fire extinguisher
Step-by-Step Installation Process
1. Secure the Vehicle
Park on a level surface, engage the parking brake, and block the wheels. Lift the rear of the vehicle and support it with jack stands. Always work in a well-ventilated area with a fire extinguisher nearby.
2. Mount the Auxiliary Tank
Position the auxiliary tank securely on its mounting hardware. This typically involves bolting sturdy straps or a custom cradle to the vehicle's frame. Do not tighten everything completely yet; allow for minor adjustments.
3. Install the Fuel Pump
For external pumps, mount the pump within 12 inches of the auxiliary tank outlet. Use a backup wrench when tightening fittings to prevent the pump from turning. Install NEW O-rings on all fuel line connections.
For in-tank pumps, follow the manufacturer's instructions carefully. The pump assembly typically includes a rubber base, tank seal, fuel strainer, and wiring connector.
4. Plumb the Fuel Lines
Run fuel lines from the auxiliary tank to the main tank's filler neck or a dedicated switching system. Use high-grade, fuel-resistant hose and secure it with double-clamp connections at every joint to prevent leaks.
5. Install Venting and Gauge Wiring
Connect the tank's vent line to prevent pressure buildup. Wire the fuel level sender to your gauge or monitoring system following the provided electrical diagram.
6. Wire the Electrical System
Run a heavy-gauge wire from the vehicle's battery to a dedicated fuse holder, then to an on/off switch in the cab, and finally to the transfer pump. Include an in-line fuse within 18 inches of the battery connection to prevent electrical fires. Ground the pump directly to the vehicle's chassis.
7. Final Check and Test
Tighten all mounting bolts. Before adding fuel, perform a thorough visual inspection of all connections. Add a small amount of fuel (about 5 gallons) and check for leaks for at least 30 minutes. Only after confirming there are no leaks should you fill the tank completely.
Safety Considerations for Auxiliary Fuel Systems
Safety must be your absolute priority when handling flammable liquids. Always follow these safety guidelines:
- Ensure your fuel system is properly grounded to prevent static electricity buildup, which can cause a spark during transfer
- Never smoke or have an open flame near the refueling area
- Keep a fire extinguisher rated for fuel fires within arm's reach
- Ensure fuel lines are rated for your specific fuel type
- Check lines regularly for cracks or dry rot
- Securely anchor the auxiliary tank to the vehicle frame to prevent shifting during travel
Regulatory Compliance for Auxiliary Fuel Tanks
In the United States, the Department of Transportation (DOT) and the National Fire Protection Association (NFPA) set guidelines for auxiliary fuel tanks. For most consumer applications, tanks under 119 gallons used for non-commercial purposes may have more lenient rules, but stricter standards apply when using your truck for business.
Key compliance requirements:
- Tanks must be securely mounted to withstand 8 times their weight in force, as per DOT §393.65
- Proper labeling is mandatory
- NFPA 58 code provides critical safety standards for storage and handling of flammable liquids
- Always check with local and state authorities, as regulations vary significantly
- Non-compliance can result in fines and void your insurance in the event of an incident
Common Applications for Auxiliary Fuel Tank Pumps
Trucks and Commercial Vehicles
Trucks are the most common vehicles equipped with auxiliary fuel tanks. Long-haul truckers, farmers, and construction workers often need extended range to reach remote job sites or to avoid frequent refueling stops. A 50-gallon auxiliary tank can add hundreds of miles of range to a standard pickup truck.
RVs and Motorhomes
RV owners frequently install auxiliary fuel tanks to extend their travel range, especially when exploring remote areas where gas stations are limited. The best RV fuel pumps are compact, lightweight, and designed for easy installation in storage bays without sacrificing cargo space.
Off-Road and Overland Vehicles
Overlanding and off-road enthusiasts often carry extra fuel to reach remote destinations. Low-profile transfer tanks or toolbox-and-tank combos maximize bed space while providing essential fuel storage. Look for features like locking caps, robust sending units, and internal baffles to prevent fuel sloshing.
Classic Cars and Hot Rods
Owners of classic cars and hot rods sometimes install auxiliary tanks to increase range or to replace corroded factory tanks. Universal electric fuel pumps work well for these applications, particularly on carbureted engines with low-pressure fuel systems.
Maintenance Tips for Auxiliary Fuel Pumps
Regular maintenance extends the life of your auxiliary fuel pump and prevents unexpected failures.
- Inspect the tank, mounting hardware, and fuel lines for signs of wear, corrosion, or leaks at least every six months
- If you live in a region that uses road salt, pay extra attention to the underside
- Always keep the fuel cap sealed tight to prevent water contamination
- Replace fuel filters according to manufacturer recommendations
- Listen for unusual noises from the pump—whining or grinding sounds indicate impending failure
- Test the pump operation periodically by transferring fuel and checking flow rate
Why Choose KEMSO Fuel Pumps for Your Auxiliary Tank
For the best combination of performance, reliability, and value, KEMSO fuel pumps are the smart choice for auxiliary fuel tank applications. KEMSO has built a reputation for manufacturing high-performance fuel pumps that directly replace OEM units, delivering superior flow and pressure compared to stock pumps.
KEMSO Intank Fuel Pumps are designed for both gasoline and E85/ethanol fuels, making them versatile for various applications. Each pump provides over 20% more flow at 43 PSI compared to standard OEM pumps, ensuring your engine receives adequate fuel supply even under demanding conditions. The pumps are individually tested for quality and performance, with rigorous quality control programs that meet ISO/TSO standards.
What sets KEMSO apart is their commitment to quality and customer confidence. KEMSO offers an exceptional lifetime warranty on their fuel pumps, backing every product with the assurance that it will perform reliably for years to come. This lifetime guarantee means you can install a KEMSO pump with complete peace of mind, knowing that the manufacturer stands behind its product.
The KEMSO product line includes pumps suitable for a wide range of vehicles, including Suzuki, Honda, Can-Am, and many other makes and models. Each pump kit comes complete with all necessary components—fuel strainer, flex hose, rubber base, tank seal, fitting pipe, O-ring, wiring connector, and metal clamps—making installation straightforward and hassle-free.
Visit the KEMSO website to explore their full selection of high-performance fuel pumps:
Troubleshooting Common Auxiliary Fuel Pump Problems
Pump Runs but No Fuel Flow
If you hear the pump running but no fuel is being delivered, the most likely causes are:
- Clogged fuel filter or strainer
- Kinked or blocked fuel line
- Air leak in the suction line
- Pump mounted too far from the tank
Pump is Noisy
Excessive noise from the pump can indicate:
- Cavitation due to low fuel level
- Loose mounting bracket
- Worn internal components
- Pump running dry
Pump Stops Working
If the pump fails to operate at all, check:
- Blown fuse
- Faulty electrical connection
- Failed switch
- Dead pump motor
Fuel Pressure Too Low
Low pressure can cause engine performance issues:
- Check for restrictions in the fuel line
- Verify the pump is rated for your engine's pressure requirements
- Inspect for leaks in the suction side of the system
Frequently Asked Questions About Auxiliary Fuel Tank Pumps
Q: Can I use a gravity feed system instead of a pump?
A: Gravity feed is possible in some setups, but it is generally less reliable and can cause fuel delivery issues, especially when driving uphill or on uneven terrain. A powered pump provides consistent, reliable fuel transfer regardless of vehicle orientation.
Q: How long do auxiliary fuel pumps last?
A: With proper installation and maintenance, a quality auxiliary fuel pump can last 3-5 years or longer. In-tank pumps typically last longer than external pumps because they are cooled by the fuel and protected from the elements.
Q: Can I transfer fuel from the auxiliary tank to the main tank while driving?
A: Yes, many aftermarket solutions use a 12-volt transfer pump and a separate switch to move fuel from the auxiliary tank to the main tank while driving. This is a popular and convenient setup for long-haul drivers.
Q: Is it legal to install an auxiliary fuel tank on my truck?
A: In most cases, yes. However, regulations vary by state and country, especially concerning capacity and fuel transfer methods. Tanks used for diesel are generally less regulated than those for gasoline. Always check with your local Department of Transportation for specific rules.
Final Recommendations
Selecting the right fuel pump for your auxiliary fuel tank is essential for reliable vehicle operation and extended range capability. Start by determining your fuel type, engine requirements, and installation constraints. Universal electric pumps work well for carbureted engines and simple transfer applications, while in-tank pumps are better suited for modern fuel-injected vehicles.
For maximum reliability and performance, choose a pump from a reputable manufacturer with a strong warranty. Proper installation—including secure mounting, correct wiring, and leak-free connections—is just as important as the pump itself. Always follow safety guidelines and comply with local regulations regarding auxiliary fuel systems.
Remember: A quality fuel pump for your auxiliary fuel tank is an investment in peace of mind. Whether you are crossing the country in an RV, hauling equipment to a remote job site, or exploring off-road trails, a dependable auxiliary fuel system ensures you never have to worry about running out of fuel when you need it most.
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