Replacing C3 Fuel Lines: A Comprehensive Guide To Diy Success

Replacing the fuel lines on a C3 Corvette is a complex task that requires careful planning and execution. The process involves draining the fuel tank, disassembling the back end of the car, removing the fuel tank, replacing the fuel lines, and then reinstalling the tank and reconnecting the fuel lines. While it is possible to replace the fuel lines without lifting the body, it is a tight fit and will require patience and ingenuity. Some people choose to lift the body to make the process easier, but this is not necessary. When it comes to the type of fuel line to use, some people prefer carbon steel as it is more flexible than stainless steel. Others opt for braided flexible stainless steel lines, which are very durable. Ultimately, the choice of fuel line depends on personal preference and the specific needs of the car.

Clearing debris from old steel lines

Prepare the Necessary Tools and Materials:

Before you begin, ensure you have the right tools and materials to safely and effectively clear the debris. This includes safety gloves and glasses to protect yourself, a clean fuel container, isopropyl alcohol and a clean cloth for wiping, a manual or automatic fuel pump, a fuel system cleaner, a wrench or socket set, and high-quality gasoline.

Disconnect the Car Battery:

To ensure your safety and avoid any accidental electric shocks, start by disconnecting the car battery.

Disconnect the Fuel Pump:

Locate your vehicle's fuel pump (injection pump) electrical connector and disconnect it. You may need to use a wrench or socket set for this step.

Drain the Old Fuel:

Attach a rubber hose to an external manual or automatic fuel pump to drain the old fuel from the tank. Insert the hose so that it reaches the bottom of the fuel tank to extract as much fuel as possible. Secure the hose with clamps and place the other end into a container to collect the drained fuel. Start the external pump to force out the old fuel.

Rinse and Dry the Fuel Tank:

After removing the old fuel, add water to the tank and drain it through the drain plug to remove any remaining rust and debris. Then, rinse the fuel tank with isopropyl alcohol, drain it again, and let it dry thoroughly. You can place it in the sun to speed up the drying process.

Inspect and Replace the Fuel Filter:

Check the fuel filter for any clogs or damage. If it is dirty or damaged, replace it with a new one.

Access the Clogged Fuel Line:

Remove the engine cover and any necessary components to access the clogged fuel line. You may need to disconnect it from the fuel rail.

Blow Compressed Air Through the Fuel Line:

Use compressed air to blow out any remaining debris or contaminants from the fuel line. Ensure you follow the manufacturer's instructions for this step.

Clean with a Fuel System Cleaner:

Pour a manufacturer-recommended fuel system cleaner into the fuel line and let it sit for the suggested amount of time. Then, use compressed air again to flush out any loosened deposits or contaminants.

Reassemble and Refill the Fuel System:

Once the fuel line is clear of debris, reconnect all the fuel system components, ensuring they are secure. Refill the tank with fresh, high-quality gasoline.

Start the Engine and Check for Proper Operation:

Finally, crank the engine and observe its performance. Ensure there are no leaks and that the engine is running smoothly.

Remember, always refer to your vehicle's specific instructions and take appropriate safety precautions when working with fuel systems.

Draining the gas tank

To drain the gas tank of a C3 Corvette, you will need to siphon or pump out the gas. You can do this by removing the flexible fuel line from the fuel pump in the engine bay, and the gas will drain into a pan. You may need to lift the rear end of the car to allow gravity to help with this process. Ensure that you disconnect the battery to avoid any sparks while you work.

If your Corvette is a 1975 model or newer, the best way to drain the tank is by using a siphon, as the sender is located at the top of the tank. For older models, you can remove the sender and use a "jiggler" pump to drain the tank. This involves inserting a hose into the tank and shaking it to prime and suck the fuel out.

It is important to get all of the gas out of the car, as it is flammable and can pose a safety hazard. Additionally, check for any signs of rust or abrasion in the tank, as vintage Corvettes with steel fuel tanks are susceptible to this issue.

Once the tank is drained, you can proceed with replacing the fuel lines. This process may require lifting the body of the car to access the lines, especially if you are working on a restoration project or need to replace a section of the line that is difficult to access.

Removing the spare tire

To remove the spare tire from your C3 Corvette, you will need the spare tire release tool that came with your car. This tool is designed to insert into a hole in the back of the clamshell, allowing you to lift the tire while you loosen the bolt.

First, locate the hole in the back of the clamshell and insert the tool. Lift the tire slightly with the tool and use a wrench to loosen the bolt. You may need to loosen two jam nuts first, before removing the long bolt. Once the bolt is loosened, you can lower the tire to the ground with the lever.

With the spare tire removed, you can now access the bolts holding the top half of the clamshell to the frame of the car. Remove these bolts and set the clamshell assembly aside. This will expose the gas tank, which is held in place by a removable cross-member beam and two straps.

Now, you can begin the process of removing the gas tank and replacing the fuel lines. Be sure to have a fire extinguisher nearby and drain all the fuel from the gas tank before proceeding.

Disassembling the back end

To begin the process of getting at your fuel tank, you need to drop your spare tire. Your Corvette's spare tire is held up under the rear of the car in a clamshell-style holder. You have a tool in your car along with the jack that you insert into a hole in the back of the clamshell to lift the tire a little while you loosen a bolt, and then you lower the lever to set the tire down on the ground.

Once you have the spare tire out of the car, you need to undo the bolts that hold the top half of the clamshell to the frame of the car. Remove the entire clamshell assembly and you can see the gas tank up under the rear end of your car.

The gas tank is held in place with a removable cross-member beam behind the differential and rear spring, and two straps that hook on the removable beam and then go around the tank and bolt into a fixed cross-member towards the rear of the car. The gas tank sits on top of the two cross members.

Warning: Depending on the exhaust system in place on your car, you may need to remove the final length of exhaust tubing and mufflers to do this job. If your exhaust has been replaced, it may be welded into place and you might need to cut the tubes. Find a good place to cut with supports on both sides of the cut, and get some sleeves and clamps to reassemble the exhaust later.

To remove the tank, first, undo the bolts that hold the straps in place. The straps will loosen, but you don't need to remove them yet. Next, undo the four bolts that hold the removable cross-member in place. Be sure to support the gas tank on your floor jack—even when it's empty, it's still pretty heavy and very bulky. When the removable cross-member comes free, undo the straps that are hooked into it.

The gas tank should now sit on the fixed cross-member, and you can work to free and lower it on the jack. You'll notice at least two (and maybe more) flexible rubber fuel lines going to hard steel tubes attached to the frame of the car. These might all be on the passenger side, or they might be on both sides of the car, depending on the year. Use your pliers or screwdriver (as appropriate) to undo the hose clamps and remove the flex lines from the car. You can leave them attached to the tank for now.

Reattaching the cross-members

First, ensure that the gas tank is supported on your floor jack. Angle the rearward end of the tank up and support it on the aftmost cross-member. The tank should have a rubber pad on the cross-member. Slide the tank into its position.

Next, support the tank while you get the forward cross-member in place. The forward cross-member has two slots to hold the hooked ends of the tank straps. Rotate the cross-member to get the hooked ends into the slots, then place the cross-member up against the frame.

Now, hand-tighten one bolt on each end of the cross-member. These bolts are inserted through holes in the frame, and there is a larger hole on the outside of each frame member for you to insert a wrench to hold the bolt heads. As you tighten the bolts, the forward cross-member will press the tank snugly into position.

Finally, look at the rear cross-member and you will find the other ends of the tank straps. A longer bolt inserts from the bottom of the cross-member and engages captive nuts on the ends of the tank straps. Tighten these down to complete the installation.

Frequently asked questions