How to Flare Fuel Line for Rubber Hose

If you have a rubber fuel hose, you may need to flare the end of the hose in order to install it properly. This process is not difficult, but it does require a few specialized tools.

Types of Fuel Line Flares

Fuel line flares are used to create a secure connection between fuel lines and components in various systems, such as automotive fuel systems. There are several types of fuel line flares, each with its own design and purpose.

The most common types of fuel line flares include:

  1. Single Flare (SAE Flare or 45° Flare): The single flare is one of the simplest types of flares. It involves forming a 45-degree angle on the end of the tubing and then creating a single flare along the edge. This type of flare is commonly used for low-pressure applications, such as brake lines and some fuel lines.
  2. Double Flare (Bubble Flare or SAE Double Flare): The double flare is a more secure and robust type of flare compared to the single flare. It involves creating a 45-degree angle on the end of the tubing, followed by a second flare formed using a specialized tool that folds the edge of the tubing back onto itself. This creates a more reliable seal and is commonly used in higher-pressure applications, including fuel lines.
  3. ISO Flare (DIN Flare or Metric Flare): The ISO flare is similar to the double flare but follows the ISO (International Organization for Standardization) standards. It’s commonly used in European automotive systems and is characterized by a 42-degree angle and a slightly thicker flare.
  4. Inverted Flare (SAE Inverted Flare): The inverted flare, also known as the SAE inverted flare, involves creating a flare on the inside of the tubing. The end of the tubing is flared outward and then threaded with a special nut that compresses the flare against the receiving component, creating a seal. This type of flare is often used in brake lines and some fuel lines.
  5. GM Quick Connect: General Motors (GM) uses a quick-connect system for some of its fuel lines. This system involves a plastic or metal connector that snaps onto a fuel line and locks into place. It’s designed for easy installation and removal.
  6. Push-to-Connect: Push-to-connect fittings are used in various applications, including fuel lines. These fittings have a simple design that allows the tubing to be inserted into the fitting, creating a secure connection through an internal gripping mechanism. This type of connection is often used in fuel systems with plastic tubing.

It’s important to note that the choice of flare type depends on the specific requirements of the fuel system, including pressure, compatibility with fuel types, and industry standards. Proper flaring techniques and tools are crucial to ensuring safe and leak-free connections in fuel lines. Always follow manufacturer guidelines and industry standards when working with fuel line flares.

How to Flare Fuel Line Without Tool

Flaring a fuel line without a dedicated flaring tool can be challenging and may not result in a proper and safe connection. Flaring tools are designed to ensure a consistent and secure flare that maintains the integrity of the fuel line. However, if you’re in a situation where you absolutely need to flare a fuel line without a tool, here’s a general method that you can attempt:

Please note that this method might not provide the best results, and it’s strongly recommended to use a proper flaring tool for safety and reliability.

Materials you’ll need:

  • Fuel line tubing (copper or steel)
  • Hacksaw or tubing cutter
  • File or sandpaper
  • Propane torch or other heat source
  • Gloves and safety goggles

Steps to Flare Fuel Line for Rubber Hose:

  1. Cut the Tube: Use a hacksaw or tubing cutter to cut the fuel line tubing to the desired length. Ensure that the cut is clean and perpendicular to the tubing.
  2. Deburring: After cutting, the edge of the tube can be jagged. Use a file or sandpaper to smooth out the cut edge. This will help create a more even surface for the flare.
  3. Heating the End: Gently heat the end of the tubing using a propane torch or another heat source. The goal is to soften the metal slightly; this will make it easier to shape the flare.
  4. Shaping the Flare: While the tubing is still hot, use pliers or another rounded object to gently shape the heated end into a flared shape. This process requires careful attention to achieve a consistent flare.
  5. Cooling and Inspection: Allow the tubing to cool down naturally or use a controlled cooling method. Once it’s cool, inspect the flare for any cracks, irregularities, or unevenness. Keep in mind that a proper flare is crucial for a safe and leak-free connection.
  6. Attach to Fitting: After confirming the flare’s shape and quality, you can attempt to connect the flared end of the tube to the appropriate fitting. Be very cautious during this step to avoid damaging the flare.
  7. Test for Leaks: Before putting the fuel line into service, it’s crucial to test the connection for leaks. Apply a soapy water solution to the connection area and observe for any bubbles. If you see bubbles forming, there’s a leak, and the connection needs to be redone.

Remember that flaring fuel lines is a critical task, as leaks can lead to dangerous situations. Using a proper flaring tool is the recommended way to achieve a secure and reliable connection. If you’re not confident in your ability to flare a fuel line without a tool, consider seeking assistance from a professional or obtaining the necessary tools for the job.

How to Flare Fuel Line for Rubber Hose


How Do You Flare Tubing for a Hose?

If you’re working with a flexible hose, it’s important to know how to flare the tubing. This will ensure a tight, secure fit that won’t leak.

Here’s a step-by-step guide on how to do it:

  • 1. Cut the tubing at a 90-degree angle using a sharp knife or tubing cutter. Make sure the cut is clean and straight.
  • 2. Deburr the inside and outside of the tubing with a deburring tool. This will remove any sharp edges that could cause problems later on.
  • 3. Place the tube in a vice so that it’s held securely in place.
  • 4. Use a flaring tool to slowly flare out the end of the tubing.

Follow the manufacturer’s instructions for your specific tool; there may be different settings or adjustments depending on the size of tubing you’re using.

Can You Use Rubber Air Hose for a Fuel Line?

No, you cannot use a rubber air hose for a fuel line. A fuel line must be made of a material that is compatible with gasoline or other fuels. Rubber is not compatible with gasoline, so it will degrade and break down over time when used as a fuel line.

This can lead to leaks or even fires.

Flaring low pressure fuel line


If you’re working with a rubber fuel line, you’ll need to flare the end in order to attach it to a fitting. This can be done with a few tools that you likely already have on hand.

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