Replacing Fuel Line At Carburetor: A Step-By-Step Guide

Replacing the fuel line at the carburetor is a common maintenance procedure for small engines. Over time, fuel lines can become brittle and crack, leading to fuel leaks. This process involves removing the old fuel line, installing a new one, and verifying that the new line is properly connected and sealed. It is important to work in a well-ventilated area and take precautions to avoid any open flames or ignition sources. Before beginning, it is recommended to drain the fuel tank and disconnect the battery to prevent accidental ignition.

How to Replace Fuel Line at Carburetor

Identify the type of carburetor

Carburetors are an essential component of older cars and trucks, mixing air and fuel in the correct proportion for the engine. There are two main types: 2-barrel and 4-barrel. The former has two primary barrels responsible for mixing air and fuel, while the latter has two additional secondary barrels for improved performance and fuel distribution in larger engines and/or engines that operate at higher RPMs.

In addition to the type, it is important to identify the specific carburetor model. Most carburetors have a unique identification number that can be used to confirm the manufacturer, model number, and specifications. These ID numbers are typically located on a metal tag attached to the carburetor or stamped/etched directly onto the carburetor body. The ID usually consists of a combination of letters and numbers that can denote the carburetor's manufacturer, model, and production date.

Holley Carburetors

Holley carburetors are popular among muscle car enthusiasts and are known for their high-performance capabilities. Their identification numbers are typically stamped on the air horn or main body. Most "list" numbers consist of a four or five-digit number, followed by a dash and an additional one or two-number suffix. This list number can then be used to look up detailed information online.

Demon Carburetors

Demon carburetors are designed for high-performance applications and come in various sizes and configurations. Their identification numbers are alphanumeric and can be up to nine digits long. They are typically stamped or etched on the air cleaner mounting ring surrounding the air entry opening. If the carburetor doesn't have a number on top, it will be more difficult to identify and may require assistance from Holley.

Edelbrock Carburetors

Edelbrock carburetors are favoured by hot rod and racing enthusiasts for their reliability and performance. Their identification numbers are typically stamped on the front ear with a four or five-digit number, denoting the Edelbrock part number. This number can then be searched online to confirm the carburetor size and additional details.

Walbro Carburetors

For Walbro carburetors, you'll almost always find the model information stamped into the body on the side opposite the jets. Most of the time, the number will be right beside the body. Occasionally, the carburetor model number may be found in the second position below the body type.

Zama Carburetors

Zama carburetors are a bit more complicated. You need to look for the body type and model number on opposite sides of the body. The body type is usually cast into the centre of the housing on the same side as the jets. To find the model number, simply turn the carburetor over to the opposite side.

Tillotson Carburetors

Tillotson carburetors can sometimes be challenging to identify definitively. On the smaller HU series, look at the air filter side of the body. The model number will usually be a regular stamping. For the body, look inside one of the circles; this will indicate the series. Sometimes, you may only find the model number, which is fine for identification.

On engines produced by manufacturers such as Briggs & Stratton, Tecumseh, and Kohler, you will likely need the engine's model information to look up the carburetor, as many of these carburetors lack any model indication.

Disconnect the fuel line

Disconnecting the fuel line from a carburetor can be done for a number of repairs and maintenance procedures. It is important to note that fuel lines need to be handled with caution as they are highly flammable.

• Park your vehicle on a flat, hard surface and engage the parking brake. Ensure that the transmission is in park for automatics or in first gear for manuals.
• Place wheel chocks, such as large rocks or blocks of wood, in front of the tires to prevent the vehicle from rolling forward.
• Using a floor jack, lift the vehicle at its specified jacking points until the wheels are completely off the ground. This will provide you with better access to the fuel line and carburetor.
• Place jack stands under the jacking points and lower the vehicle onto them. This will ensure the vehicle is stable and secure during the repair process.
• Disconnect the battery by opening the vehicle's hood and removing the ground cable from the battery's negative post. This will disable the power to the ignition and fuel system, reducing the risk of accidental ignition.
• Locate the fuel hose that needs to be replaced. If it is damaged or leaking, place a small drip pan underneath to catch any remaining fuel.
• Using a flathead screwdriver, remove the hose clamps that hold the fuel hose in place. You may need to use a pair of pliers to lightly grab and twist the hose as you pull it off.
• Carefully pull the fuel hose off the attaching fuel line, fuel pump, or carburetor. If the hose is difficult to remove, consider using a sharp knife or razor blade to carefully split the hose near the fitting.
• Once the fuel hose is removed, clean the surface that it was attached to using a lint-free cloth. This will ensure that any residual fuel or debris is removed before installing the new fuel hose.

It is important to note that different vehicles may have slightly different procedures for disconnecting the fuel line. Always refer to the specific instructions for your vehicle's make and model. Additionally, working with fuel can be dangerous, so ensure you take the necessary precautions and have the appropriate safety equipment.

Remove the fuel tank

Removing the fuel tank is a complex process and it is recommended that you have an assistant to help you with the task. Before you begin, ensure you have the necessary tools and equipment. These include strap bolts, slotted and Phillips screwdrivers, special tools for disconnecting fuel line fittings, a jack, jack stands, a pump for removing the fuel, fuel-rated containers, rags, and a fire extinguisher.

First, locate your vehicle on a flat surface, preferably a concrete driveway, and ensure you have access to repair parts. Disconnect the ground cable of your battery to avoid sparks. Next, drain the fuel from the tank into a container. Most fuel tanks have a 12 to 20-gallon capacity, so ensure your container is large enough. If your car has a drain plug, remove it carefully to avoid spilling fuel. If not, locate the tank's drainpipe or filler hose and connect an intake hose from a pump to the pipe. Place the discharge hose of the pump into the gas container and extract the fuel. Seal any openings to prevent vapors from escaping.

Now, you can begin to remove the fuel tank. Chock the front wheels of the car to prevent it from rolling, and lift the vehicle with a jack. Once it is high enough, support it with jack stands. Blow compressed air to remove debris from the outside of the fuel lines and wiring connectors. Place a mat or a sheet of plywood underneath the car for your comfort and to prevent losing fasteners.

Disconnect the fuel tank wiring harness connector and the ground wire screw from the chassis if your vehicle has one. Remove the fuel lines from the gas tank, and wipe off the filler and vent pipes with a soft towel before disconnecting their tubes. Unhook the filler neck by removing the screws around it or loosening the clamp and removing the hose.

Locate the fastening system that holds your fuel tank in place, usually two straps that wrap around the tank and bolt to a bracket. Loosen these bolts until the tank is only just supported, and carefully lower the tank to the ground as you finish loosening the bolts. Remove the straps from around the tank, and pull the tank out from under the car.

Install the new fuel line

To install the new fuel line, you will need a flathead screwdriver, a fuel transfer tank with a pump, and a ratchet with metric and standard sockets.

First, place new hose clamps around the new fuel line. Ensure that the clamp is installed at the proper tightness. Then, install the new fuel line onto the fuel pump, fuel line, or carburetor. Tighten the new hose clamps and secure the hose. Do not use old hose clamps as the clamping force will not hold when tightened, causing a leak.

If your vehicle is an older model from before 1996, you will need to install the new fuel line onto the fuel line and fuel pump. Raise the fuel tank and, if your vehicle has a fuel filter, snap the fuel line to the filter, ensuring that the connections are tight. Install the mounting bolts to the fuel filler neck, tightening them finger-tight and then turning them an additional 1/8 turn. Put Loctite on the threads of the mounting bolts and tighten them up hand-tight, followed by another 1/8 turn to secure the straps.

For vehicles from 1996 onwards, snap the quick disconnect together onto the fuel line by the firewall. Then, snap the quick disconnect together from the fuel line to the fuel rail, ensuring that both connections are sealed tight.

If you are installing all three lines, install the vapor line to the charcoal canister and the return line to the fuel tank by snapping the quick disconnect together. Raise the fuel tank and align the fuel filler neck so it can be mounted. Install the mounting bolts to the fuel filler neck, tightening them finger-tight and then turning them an additional 1/8 turn. Put thread locker on the threads of the mounting bolts and tighten them up hand-tight, followed by another 1/8 turn to secure the straps.

Finally, snap the quick disconnect on the fuel hose to the fuel line. This can be found behind the firewall in the engine compartment.

Test for leaks

Once you have replaced the fuel line at the carburetor, it is important to test for leaks. Here is a step-by-step guide:

• Reconnect the ground cable back to the battery's negative post. Remove any battery savers you used during the fuel line replacement.
• Tighten the battery clamp to ensure a good connection.
• Turn the ignition key on. Listen for the fuel pump to activate, then turn off the ignition after the fuel pump stops making noise.
• Cycle the ignition key on and off 3 to 4 times to ensure all the fuel lines are full of fuel.
• Use a combustible gas detector to check all the connections for any leaks.
• Sniff the air for any fuel odours.

If you do detect a leak, you may need to tighten the connection at the carburettor. If the leak persists, the connection fitting is probably bad and it may be time to replace the fuel line again.

If you are working with a 2-cycle engine, there are specific steps you can take to test for correct fuel line installation:

• Install the lines and test the orientation. Guess the correct orientation and install the lines on the carburettor.
• Test the orientation of the fuel lines by placing the ends of both lines in 2-cycle fuel (never water) and then prime the bulb.
• If fuel is pushed out of the unfiltered line, then the orientation was guessed correctly.
• If bubbles emerge from the line with the fuel filter, then the lines were installed incorrectly. You must switch the lines and test again.

Frequently asked questions