The Transfer Flow Fuel Pump: Your Essential Guide to Auxiliary Fuel Transfer Systems

Transfer Flow fuel pumps are specifically engineered, high-performance secondary fuel transfer systems designed primarily for diesel trucks equipped with auxiliary fuel tanks, offering unmatched reliability, safety, and high-volume fuel transfer capabilities for long-haul, remote work, or overlanding needs.

If you rely on a diesel truck for long distances, heavy towing, remote job sites, or recreational adventures far from fuel stations, maximizing your fuel range is critical. An auxiliary fuel tank is often the solution. However, getting that fuel reliably and safely from the auxiliary tank into your main truck tank requires a dedicated transfer pump. Not just any pump will do. Transfer Flow Inc. has established itself as the leader in this specific field, developing purpose-built transfer pumps known for their robust construction, consistent performance, and integrated safety features. Understanding the Transfer Flow fuel pump – its function, benefits, operation, and why it differs from generic alternatives – is essential knowledge for anyone considering or currently using auxiliary fuel capacity.

Core Function: Transferring Fuel from Auxiliary to Main Tank

The fundamental role of a Transfer Flow fuel pump is straightforward: to move diesel fuel from a secondary (auxiliary) fuel tank installed on your vehicle into the vehicle's primary, factory-installed fuel tank. This is not the same as the truck's primary engine lift pump that feeds the high-pressure injection system. The transfer pump operates independently, controlled by the driver or automated systems, specifically for moving fuel between tanks. This process effectively extends the operational range of the vehicle without requiring immediate stops at fueling stations.

Why Diesel Trucks are the Primary Application

While transfer pumps can theoretically be used for gasoline or other liquids, Transfer Flow designs and markets its pumps primarily for the diesel truck market. Diesel trucks are the main platform needing substantial extended range solutions due to:

  1. High Fuel Consumption: Diesel engines, especially under heavy loads or when towing, consume significant fuel, quickly depleting the standard factory tank.
  2. Long-Distance Towing/RV Support: Trucks towing large trailers or fifth-wheels experience drastically reduced fuel economy, making auxiliary fuel crucial for practical travel distances.
  3. Remote Operations: Work trucks in construction, agriculture, energy exploration, and forestry often operate far from readily available fuel supplies for extended periods.
  4. Space Availability: Diesel trucks (pickups, flatbeds, service bodies) typically have the frame space and payload capacity necessary to mount substantial auxiliary tanks securely.

Defining the Auxiliary Tank Requirement

The Transfer Flow fuel pump is intrinsically linked to the auxiliary tank system. This auxiliary tank is an additional fuel storage unit installed on the vehicle, separate from the primary factory tank. Common locations include the truck bed, underneath the bed, or mounted to the frame rails. Sizes vary significantly, ranging from smaller 40-gallon units to very large 150+ gallon tanks, depending on vehicle space, payload limits, and required range extension. The transfer pump is physically mounted to or integrated with this auxiliary tank system. Its job is solely to transfer fuel from here into the main tank.

Key Differentiators: Reliability and Safety

Transfer Flow fuel pumps distinguish themselves from generic transfer pumps through an intense focus on reliability and safety, critical factors when dealing with large volumes of flammable diesel fuel on a moving vehicle.

  1. Rugged Construction: Built using high-grade materials like anodized aluminum housings and stainless steel components to withstand harsh environments, vibration, corrosion, and prolonged exposure to diesel fuel. They are designed for a long service life under demanding conditions.
  2. Integrated Safety Features: A hallmark of Transfer Flow pumps is the inclusion of vital safety mechanisms:
    • Fuel Level Sensing: Uses the truck's existing fuel gauge system or dedicated gauges to prevent dangerous overfilling of the main tank during transfer.
    • Automatic Shut-off: When the main tank reaches full (or a designated safe level), the pump automatically stops transferring fuel. This eliminates the risk of driver distraction leading to a hazardous overflow.
    • Thermal Protection: Built-in thermal protection circuitry guards the pump motor against overheating due to excessive duty cycles or blockages, preventing burnout and potential fire hazards.
    • Robust Wiring & Connectors: High-quality wiring harnesses designed for automotive environments, minimizing risks of shorts, sparking, or connection failure.
  3. Designed for Automotive Use: Unlike generic industrial pumps, Transfer Flow pumps are engineered specifically for mounting on vehicles. They consider vibration resistance, compact form factors, vehicle electrical systems (12V or 24V DC), and integration with existing truck wiring and gauges.

High-Performance Fuel Transfer

Transfer Flow pumps prioritize efficient and rapid fuel movement:

  1. High Flow Rates: These pumps are designed to move significant volumes of diesel quickly. Flow rates typically range from 15 to 50+ gallons per hour (GPH), ensuring you can transfer enough fuel during a reasonable break or short stop to make a substantial impact on your range.
  2. Consistent Pressure: Maintain appropriate pressure throughout the transfer process to ensure smooth, reliable fuel movement into the main tank without cavitation or flow interruptions.
  3. Efficient Operation: Optimized motor and impeller/gear designs minimize power draw while maximizing fuel throughput. This reduces load on the vehicle's electrical system.
  4. Durability: Built using diaphragm or gear pump technologies known for handling diesel fuel reliably over long periods. Materials resist degradation from fuel additives and environmental contaminants.

Types of Transfer Flow Pump Systems

While the core pump technology is fundamental, Transfer Flow integrates it into user-friendly systems:

  1. Manual Control Systems: The simplest setup. Typically involves a dedicated dash-mounted switch (often with an indicator light) that the driver activates to start the transfer process. The pump runs until the operator turns it off or until the main tank's automatic shut-off level is reached. Requires driver attention.
  2. Semiautomatic Systems: These systems often include a timer function. The driver presses a button to start the transfer, and the pump runs for a pre-set amount of time (e.g., 10 minutes) before automatically shutting off. This adds an extra layer of overflow prevention beyond the main tank sensor. The pump will also shut off if the main tank sensor detects full.
  3. Fully Automatic Systems: The most sophisticated option. A dedicated controller constantly monitors the fuel level in both the auxiliary and main tanks. When the main tank fuel level drops below a preset threshold (e.g., 3/4 full), and the auxiliary tank has sufficient fuel, the system automatically initiates a transfer until the main tank reaches full. No driver intervention is needed beyond initial setup and monitoring fuel levels.

The Critical Bypass System (Fuel Return Line)

A crucial component often integrated with Transfer Flow pumps, especially for seamless transfer into modern diesel main tanks, is the bypass system. Modern diesel engines continuously circulate a large volume of fuel – only a small amount gets injected; the rest returns to the tank. If you try to pump fuel into the main tank while the engine is running, the return flow creates positive pressure, resisting the incoming transfer and causing slow fill times or complete blockage.

The Transfer Flow bypass system elegantly solves this:

  1. Tee Connection: It incorporates a tee fitting into the vehicle's factory fuel return line.
  2. Diversion Valve: During transfer mode, a solenoid valve actuates.
  3. Diversion: Instead of returning fuel to the main tank, the bypass system diverts the entire engine fuel return stream into the auxiliary tank.
  4. Overcoming Pressure: This eliminates positive pressure buildup within the main tank.
  5. Simultaneous Operation: Fuel can now flow freely into the main tank while the engine continues to run and return fuel to the auxiliary tank. Transfer times become significantly faster and more reliable.
  6. Automatic Switching: In fully automatic Transfer Flow systems, the diversion valve operates seamlessly with the transfer pump, triggered by the controller.

Installation Considerations: Not a Simple Plug-and-Play

Installing a Transfer Flow fuel pump system, including the auxiliary tank and associated plumbing/electrical connections, is a significant undertaking. Key points:

  1. Tank Compatibility: The pump is designed to work optimally with Transfer Flow auxiliary tanks or compatible tanks engineered to work with their systems. Matching the pump to the tank design is critical.
  2. Vehicle Integration: Mounting the tank securely requires understanding frame rail configurations and payload capacity. Routing fuel lines and wiring harnesses safely away from heat, moving parts, and potential abrasion points is complex.
  3. Plumbing Expertise: Cutting into the factory fuel lines, installing the bypass tee correctly into the high-pressure return line, and ensuring leak-proof connections requires precise work and knowledge of diesel fuel systems.
  4. Electrical Integration: Connecting the pump controller, switch, solenoids, and sensors into the vehicle's electrical system safely requires proper fusing, gauge wiring, and secure grounding.
  5. Sensor Calibration: Calibrating the tank level sensors for both the auxiliary tank and the main tank sensor override is necessary for accurate readings and reliable automatic shut-off.
  6. Professional Recommendation: Due to the complexity and safety implications, Transfer Flow and industry experts strongly recommend professional installation by authorized dealers or experienced diesel technicians. An incorrect installation can lead to fuel leaks, pump failure, electrical problems, and severe safety hazards.

Operational Use in Real-World Scenarios

Understanding how to effectively use the system matters:

  1. Transfer Timing: Most users prefer to transfer fuel while the vehicle is parked and stationary. While some systems can function while driving (especially automatic ones), parked transfer is generally safer and avoids potential complications from sloshing fuel or uneven roads. Refueling during rest stops, meals, or mandatory breaks is common.
  2. Monitoring: Even with automatic shut-off features, it's prudent to periodically check both the main tank and auxiliary tank gauges during operation. Monitor the system's behavior after installation to ensure everything functions as expected.
  3. Impact on Range: Adding an auxiliary tank significantly increases the vehicle's operational radius. For example, a 60-gallon auxiliary tank effectively doubles the range of a truck with a 60-gallon main tank. This translates to fewer fuel stops, saving significant time on long trips or in remote areas where stations are scarce and expensive.
  4. Cold Weather Operation: Transfer Flow pumps are designed for typical diesel operating temperatures. However, like all diesel systems, using appropriate winter-blend fuel or additives is necessary in freezing conditions to prevent fuel gelling that could affect pump operation.

Long-Term Maintenance and Care

While built for durability, Transfer Flow fuel pumps benefit from basic care:

  1. Quality Fuel: Using clean, high-quality diesel fuel is paramount. Contaminants like dirt or water accelerate wear and can clog filters or damage pump internals.
  2. Fuel Filter Attention: Most Transfer Flow pump systems include an inline fuel filter on the suction side of the pump. This filter protects the pump from debris drawn from the auxiliary tank. Regular inspection and replacement of this filter according to the manufacturer's schedule are essential for maintaining flow rates and pump longevity. Neglecting this filter is a primary cause of pump failure or reduced performance.
  3. Visual Inspection: Periodically check all visible fuel lines, connections, wiring harnesses, and the pump itself for signs of leaks, chafing, or damage.
  4. Unclogging Vents: Ensure the auxiliary tank's vent lines are clear and unobstructed. Blocked vents will cause transfer difficulties or pump cavitation.
  5. Motor Brushes (If Applicable): While designed for long life, some pump motors have replaceable brushes. Understand your specific pump's maintenance needs.

Addressing Common Issues

Even reliable systems can encounter problems:

  1. Pump Won't Run: Check basics first: ignition status (some require ignition on), main fuse, controller fuse, switch operation, and electrical connections (grounds are frequent culprits). Verify sufficient fuel in the auxiliary tank.
  2. Pump Runs But No/Slow Transfer: Suspect a clogged suction filter or a blockage in the suction line. Also, check for kinked fuel lines, incorrect bypass valve operation, or a stuck check valve. Verify the auxiliary tank vent is clear.
  3. Pump Doesn't Shut Off (No Auto-Stop): Likely an issue with the main tank sender connection or circuit. Check wiring, connector pinches, or faulty sender/sensor. Confirm proper calibration. Never ignore an auto-shutoff failure – turn the pump off manually immediately.
  4. Excessive Noise or Vibration: Can indicate cavitation (lack of fuel at suction – check filter, vent, pickup, tank level), air in the lines, impeller damage, or loose mounting.
  5. Fuel Leakage: Requires immediate attention. Identify the source – connections, pump seals, tank fittings, or lines. Do not operate the system until repaired.

The Investment Value

Transfer Flow fuel pumps and auxiliary tank systems represent a significant investment. The justification lies in:

  1. Time Savings: Drastically reduces time spent locating and stopping for fuel, especially important for commercial drivers, fleet operations, and overlanders covering vast distances. More time driving and less time fueling directly impacts productivity and trip timelines.
  2. Increased Productivity: For work trucks, longer range means fewer interruptions, less downtime returning for fuel, and the ability to work in areas without readily available diesel. Can also allow smaller fuel trailer requirements on job sites.
  3. Reduced Fatigue: Knowing you have ample fuel reserves reduces stress and driver fatigue associated with constantly calculating distances to the next station, especially when towing or in unfamiliar territory.
  4. Cost Efficiency: While the upfront cost is high, bulk fuel purchases (filling both tanks at once) often offer per-gallon savings compared to frequent small fill-ups at remote or truck-stop locations. Eliminating long detours to reach fuel stations saves fuel and time.
  5. Safety Enhancement: Reliable range extension keeps vehicles operational and avoids potentially dangerous situations like running out of fuel in isolated or hazardous locations.
  6. Quality and Warranty: Transfer Flow backs its pumps with warranties, supporting the promise of reliability. The use of high-quality materials ensures longevity.

Choosing the Right Transfer Flow Pump System

Selecting the optimal system depends on specific needs:

  1. Tank Size & Capacity: Determine the range extension needed realistically, considering payload capacity and vehicle space constraints. Match pump flow rates to the tank size (larger tanks often pair with higher GPH pumps).
  2. Control Preference: Decide between manual, semiautomatic, or fully automatic operation based on desired convenience level and budget.
  3. Vehicle Specifics: Provide exact vehicle details (year, make, model, engine) to Transfer Flow or an authorized dealer to ensure compatibility, especially concerning fuel line types (return location/type) and wiring requirements.
  4. Application: Heavy commercial use vs. occasional RVing might influence robustness and feature requirements.
  5. Professional Consultation: Work with an authorized Transfer Flow dealer. They have the expertise to recommend the correct pump/tank/controller combination for your vehicle and usage, handle complex installations, and provide warranty support.

Why Transfer Flow Leads the Market

Transfer Flow Inc. has focused exclusively on fuel storage and transfer solutions for diesel trucks for decades. This specialization translates into:

  • Deep Application Knowledge: Intimate understanding of truck platforms, fuel systems, and driver needs.
  • Integrated Systems: Designing tanks, pumps, controllers, and accessories to work together flawlessly.
  • Compliance: Ensuring systems meet relevant safety standards and regulations.
  • Robust Engineering: Prioritizing durability and reliability above all else.
  • Comprehensive Support: Network of authorized dealers for sales, expert installation, and warranty service.
  • Continuous Innovation: Developing features like the integrated bypass and advanced controllers.

For diesel truck owners requiring extended range solutions, the Transfer Flow fuel pump is not just an accessory; it's the reliable, safe, and high-performance heart of a practical auxiliary fueling system. By moving large volumes of fuel efficiently, integrating critical safety features like automatic shut-off and thermal protection, and enabling the use of vital bypass systems, it addresses the core challenges faced by long-haul truckers, RV enthusiasts, and heavy-duty work fleets. Investing in this capability, supported by professional installation and proper maintenance, delivers substantial returns in saved time, reduced stress, enhanced productivity, and the invaluable security of extended fuel autonomy in any driving environment.

Back to blog