Repairing High-Pressure Fuel Lines: A Step-By-Step Guide

A broken high-pressure fuel line can be dangerous and requires immediate attention. The repair process will depend on the type of fuel line in your vehicle, as modern vehicles use fuel injection systems with fuel line pressures of 45 to 60 PSI, while older carbureted vehicles use lower pressures of 4 to 8 PSI. It is important to note that quick fixes like duct tape, glue, or sealant are not suitable for high-pressure fuel lines due to the temperature and pressure of the fuel. The safest approach is to replace the damaged section of the fuel line or the entire line itself.

For nylon fuel lines, a repair kit is available at auto parts stores, which includes blocks, a gun, and a nylon tubing cutter. The process involves securing the lines with the blocks, using a tapered connector to join the lines, and ensuring a leak-free connection. Metal fuel lines can be repaired using a tubing bender and a tubing cutter to make precise cuts and bends for a secure connection. It is recommended to use compression fittings or flare the line for splicing.

Safety precautions are crucial when repairing fuel lines. Always work on a cool engine, prevent accidental fires, avoid electric tools, and properly dispose of gasoline-soaked rags.

Repairing a Broken High-Pressure Fuel Line

Find the leak

To repair a broken high-pressure fuel line, you must first find the leak. Here are some steps to help you locate the source of the problem:

• Start by turning off the engine and allowing the car to cool down. This is important for safety reasons, as you don't want to risk accidental burns while working on the fuel line.
• Look for signs of leakage around the rubber fuel line. If there is a leak, you will need to replace the entire rubber hose or parts of it. No amount of duct tape, glue, or sealant will fix a leak properly due to the temperature and pressure of the fuel.
• Loosen the clamps at both ends of the rubber hose with a screwdriver. Remove the clamps and carefully detach the hose from the metal connections.
• Use rags to catch any gasoline that leaks from the hose or connections.
• If the tubing doesn't come off easily, use pliers to pull it from the connection.
• Make a small incision (about one inch) from the end of the tubing along its length using a razor blade or knife. This will help loosen the rubber and make it easier to remove from the connection.
• Once the hose is detached, take it to an auto parts store to get a replacement. Bring the rubber line and clamps with you so that the specialist can provide the correct diameter line and new clamps.
• Purchase a rubber tubing of the same length as the one you removed, adding about two extra inches. You can always trim the line if it's too long, but you can't add length once it's cut.

Remember, safety should be your top priority when working on a fuel line. Make sure to work in a well-ventilated area, avoid smoking near the vehicle, and keep children and pets away from the work area.

Remove the damaged line

To remove the damaged line, start by locating the leak in the rubber fuel line. Ensure that the engine is off and the car is cool to prevent accidental burns and allow for safer working conditions. Once the leak is located, loosen the clamps at both ends of the rubber hose with a screwdriver. Remove the clamps and carefully detach the hose from the metal connections. Use rags to soak up any gasoline that leaks from the hose or connections. If the tubing does not come off easily, use a pair of pliers to gently pull it free.

With the hose detached, use a razor blade or knife to cut a one-inch incision from the end of the tubing along its length. This will help loosen the rubber and make it easier to remove from its connection. After making the incision, carefully wiggle the hose to fully detach it from the connection.

Now that the damaged hose has been removed, take it to an auto parts store to purchase a replacement. It is recommended to replace the entire piece of rubber hose for the easiest repair. Be sure to also purchase new clamps to secure the new hose. When purchasing the new rubber tubing, it is important to get the same diameter line and two additional inches in length. You can always trim the line if needed, but you cannot add length once it is cut.

Purchase a replacement

If you need to purchase a replacement high-pressure fuel line, there are several options available.

Firstly, it is important to note that fuel lines come in a variety of materials, including rubber, plastic or carbon fibre, steel, aluminium, and nylon. The type of fuel line you need will depend on your vehicle's specifications and the location of the line.

For instance, rubber fuel hoses are more common in older vehicles and diesel industries, as they are adjustable and need to be moved frequently. Plastic or carbon fibre hoses are the most common type used in modern vehicles. Steel and aluminium hoses, also known as fuel lines, are found in both older and newer vehicles and can withstand high pressure, but they are susceptible to bending and kinking, which can cause restrictions and ruptures.

You can purchase fuel lines from auto parts stores or online retailers. When purchasing a replacement, ensure you have the correct measurements and specifications for your vehicle's fuel line, including length, diameter, and type of connector. It is also recommended to replace all three lines (supply, return, and vapor) if only one hose is damaged, especially if they are rubber or flex hoses.

Additionally, it is advised to use original manufacturer equipment (OEM) for replacement fuel hoses, as aftermarket products may not align correctly or have the proper quick disconnect fittings.

• 3/8 Inch (10mm) ID Fuel Line Hose 10FT NBR Rubber Push Lock Hose High Pressure 300PSI for Automotive Fuel Systems Engines
• Fuel Line Hose 5/16 Inch ID, Fuel Hose 10FT, J30R7 Fuel Line Hose NBR for Automotive Fuel Systems Engines
• Dorman 904-965 Intermediate Front Fuel Injector Line Compatible with Cadillac/Chevrolet/GMC Models
• Fuel Line Hose 5AN 5/16" High Pressure Hose 2.8Mpa 400PSI 8mm 5FT for Fuel Systems Engines Tube Hose Blue (Attached Hose Clamp)
• 20 Ft Fuel Line Hose, 3/8" ID x 2/3" OD NBR Rubber Hose, High Pressure 300 PSI Boat Fuel Tube for Motorcycles, Marine Boat Outboard, Automotive Fuel Systems Engines

Cut the line to size

When repairing a broken high-pressure fuel line, it is important to cut the line to size accurately to ensure a leak-free connection. Here is a detailed guide on how to cut the line to size:

First, you need to assess the damage and identify the broken or faulty section of the fuel line. This could be due to rust, rot, or a leak. Once you have located the problem area, use a tubing cutter or a small hacksaw to remove the damaged section of the line. Make sure you have a drip pan underneath to catch any fuel that may drip from the line.

When cutting the line, it is crucial to leave at least 3 inches of straight line on each side of the damaged area. This will provide enough space to install the compression fitting securely. If you are repairing a metal fuel line, you can use a handheld tubing bender to create any necessary bends for a proper fitment.

Now, measure the distance between the two straight ends and add about 6 inches to this measurement. This additional length will give you some wiggle room in case of any mistakes. Purchase a new section of fuel line with the same diameter and material as the original line. You can find these at most auto parts stores.

Using the measurement you took, cut the new section of the fuel line to size. It is better to cut slightly longer than shorter, as you can always trim the line down if needed. Once you have the new line cut to size, you can begin the process of installing the compression fitting.

Follow the instructions provided with the compression fitting to securely join the two straight ends of the fuel line. Make sure to tighten all connections and check for leaks before starting the engine.

Remember, working on a fuel line can be dangerous, so always take the necessary precautions. Drain the fuel tank or relieve the fuel pressure before starting work, and keep any sources of ignition away from the work area.

Reattach the new line

Once you have purchased the correct size line or fitting, along with the tapered fuel line connector, you are ready to reattach the new line.

Firstly, hold the replacement line in position and mark where to cut the line. Use the nylon line cutter and remove the line. Place the opposing ends of the fuel lines into the block’s threaded side first, allowing a quarter of an inch to protrude.

Next, place a small amount of oil on the tapered connector and place the connector end in one side of the fuel line. Squeeze the handle on the tool, bringing both blocks together, and align the connector with the opposing fuel line.

Finally, squeeze the handle until the connector is fully seated on all three steps in both ends of the fuel line. Remove the tool.

If you are repairing a metal fuel line, you will need a short handheld tubing bender and a tubing cutter. Make any necessary bends for a proper fitment. Hold the replacement line in place and cut an additional inch off the original line to account for the compression fitting. Separate the parts of the compression fitting. Place one perforated cap on the original line with the threads facing out. Install the ferrule (ring) over the line in front of the cap. Push the original fuel line with the ferrule and cap into the centre section of the connector. Hold the connector and push the line until it is completely seated in the centre section. Thread the cap onto the centre section of the connector, ensuring you maintain sufficient pressure on the fuel line. Keep the line seated in the centre section while tightening the cap. Install the cap and ferrule on the opposite end and tighten in the same manner.

Turn the key on and check for leaks.

Frequently asked questions