How To Refresh Your C3 Corvette Gas Tank in 8 Mostly Easy Steps

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How To Refresh Your C3 Corvette Fuel Tank in 8 Mostly Easy Steps

Corvette Restoration Guide
You'll want a set of good repair and restoration guides for your year and model of Corvette before you begin this procedure. The detailed information for each particular type of Corvette is important to have!.

Like all cars, Corvettes have fuel tanks - and vintage Corvettes have steel fuel tanks that are subject to rust and abrasion over the years. Many older Corvettes have had their tanks replaced at least once since they were new, and many more are in need of replacement.

Even more often, the flexible fuel lines that connect the fuel tank to the hard steel fuel lines that run along the car's frame are likely to be rotten in cars over 20 years old. These lines often seep and weep fuel long before they burst open and leak gas all over the floor - so if you've been smelling gas around your Corvette, chances are good that your fuel lines are cracked.

Fortunately, replacing your vintage third-generation Corvette's fuel tank (1968-1982) is something you can do at home if you're reasonably handy. The precise instructions will differ from model year to model year, so as always be sure to get yourself a good repair and assembly manual for your particular Corvette. But the basics are all the same, so read this article and then you can decide if this is a task that you want to undertake.

NOTE: The procedure is likely to be similar for C1 (1953-1962), C2(1963-1967), and C4 (1984-1996) Corvettes, but I didn't have access to these to test these instructions. So if you have one of those models, you'll really need to depend on your repair manual.

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Tools and Supplies

1977 Corvette
This 1977 Corvette is a perfect example for this project, because it's not been carefully kept up and the fuel hoses are leaking!. Photo by Jeff Zurschmeide

You'll need a few basic tools to perform this task, and some supplies. The tools are simple -

  • A good floor jack
  • The spare tire release tool from your car
  • Wrenches and sockets from ¼-inch up to ½-inch and 9/16-inch sizes.
  • A pair of pliers​
  • Philips screwdrivers

You should also have a ten-pound ABC fire extinguisher around, just in case.

For supplies, you will need about 3 feet of ¼-inch fuel hose. Don't just use rubber hose - get the stuff that's made to handle fuel, or you'll be doing this job again sooner than you'd like. You may also need a length of 3/8-inch hose, depending on your model year. You should also order a replacement spill collector and drain line while you've got an easy chance to renew it.

Also, take a look at this article on fuel tank installation by our About.com Guide To Auto Repair, Matt Wright.

To prepare for this job, give yourself plenty of room to work. You don’t need to jack up the car, but you will need some space behind the car. Set your fire extinguisher nearby and drain all the fuel from the gas tank. You might need to siphon or pump out the gas, but if you remove the flexible fuel line from the fuel pump up in the engine bay, the gas will often drain right into a pan for you. You can lift the rear end of the car to let gravity help, if you need to. You really want all the gas out of the car, because it’s heavy and flammable.

IMPORTANT: Disconnect the battery at this time, because you don’t want any sparks while you’re working!

03
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Disassemble the Back End

1977 Corvette Fuel Tank
This is the forward cross-member supporting a 1977 Corvette fuel tank. When you remove it and loosen the strap bolts on the rear cross-member, the gas tank will fall out of the car. Photo by Jeff Zurschmeide

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 sit on the fixed cross-member, and you can now work it 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.

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Inspect the Tank

Corvette Fuel Tank Spill Drain
This is the drain line from the spill collector around the fuel neck. Note that it's clamped to the car. You may need to loosen this clamp to remove the line. Photo by Jeff Zurschmeide

With your fuel tank out of the car, you can inspect it thoroughly - and you can usually tell a rusty tank even before you look inside it with a flashlight. But if you have any doubts, a new tank costs less than $300 from most Corvette supply stores.

NOTE: One thing you might find, if the fuel tank is original to the car, is a "Tank Sticker" on the top of the tank. This is the original factory build sheet, showing every option that was built into the car at the factory. Having this sheet is a major win for proving your Corvette's provenance, as it will list the original engine, all options, and the original color scheme. Photograph the tank sticker if you plan to reinstall the same tank.

You'll find a rubber spill collector attached to the fueling neck of the tank, with a drain line running alongside the tank. This is an inexpensive item, and you should replace it while you've got the tank out.

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Replace the Fuel Lines

1977 Corvette Fuel Tank
The fuel lines on a 1977 Corvette fuel tank. You can see the two lines (1/4-inch and 3/8-inch) heading for the right side of the car, and the Tee fitting connecting two lines to a single line headed for the left side of the car.

With the tank out of the car, you can see the fuel lines. There are two to four of them attached to the tank in various places. I won’t try to describe them in detail because Chevrolet changed things substantially over the years, so there’s no way of knowing what yours may look like. But the good news is that they’re all 1/4-inch or 3/8-inch fuel grade hose. Get yourself a length of hose in the size(s) you need.

On my 1977 corvette, I needed about 18 inches of 3/8-inch hose, and about 3 feet of 1/4-inch hose. There was one nylon T-fitting and four connections to the tank. Simply measure each length of hose and cut a new length in the correct size and reassemble the hoses in the same pattern. If you have trouble getting the old hoses off the tank, you can carefully slice them away, but be sure you don’t gouge the fittings! You can reuse the existing hose clamps if they’re in good shape, or put new ones on the car.

TIP: Check the wire connections to the fuel tank sender while you’re there, and freshen them up if they need attention. If your fuel gauge isn’t working, there’s a good chance you don’t need a new sender – just a better connection for these wires!

When the new lines are installed and arranged, you’re ready to put the tank back in the car.

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Reinstall the Tank and Connect the Fuel Lines

Corvette Right Side Fuel Lines
There are two fuel lines on the right (passenger) side of this 1977 Corvette. The larger line is 3/8-inch fuel hose and the smaller line is a 1/4-inch fuel hose. Your design may vary, but you can see the hoses connecting to the hard lines on the frame. Photo by Jeff Zurschmeide

To reinstall the tank, first replace the metal straps, making sure they run under the hoses. You can use a little duct tape to hold them in place while you work. Then you can bench-press the tank up into place if you're reasonably strong, but it's easier to use your jack to lift - especially if you didn't get all the gas out of it to begin with!

When you get the tank mostly lifted into place, you should be able to route the hoses up to the hard lines attached to the frame members, and you should be able to make the wiring connection for the fuel level sender. Attach and tighten the hoses while you still have room to work. On 1974 and later cars, it may be more convenient (but a lot of work) to remove the rear bumper cover from the car, which provides excellent access to the hard lines.

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Reattach the Cross-Members

Corvette Fuel Tank Strap
You can see how the tank retaining strap hooks into the forward cross-member. You tighten the strap with the bolt on the rearward cross-member. Photo by Jeff Zurschmeide

As you lift the tank into place, angle the rearward end up and support the tank on the aftmost cross-member. It should have a rubber pad on the cross-member. The tank should easily slide into its position. 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 and then place the cross-member up against the frame. Hand-tighten one bolt on each end of the cross-member. Note that these bolts are simply inserted through holes in the frame, and there's 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. Then 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.

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Reassemble The Car

Fuel Tank Sender Wires
This is the connection from the fuel tank sender wires to the car's wiring harness. Be sure to reconnect this as you reassemble your car or you won't have a fuel gauge!. Photo by Jeff Zurschmeide

Now connect your battery and pour some gas - maybe 5 gallons or so - into the car. Make sure it's not leaking anywhere, check the fuel gauge, and fire up the car. Let it run a few minutes to make sure everything's working properly. If you took off the mufflers, it's going to be loud!

With the gas tank in place, you can reinstall the rear bumper cover (if you removed it) as well as the clamshell and spare tire. Then reinstall your exhaust if you had to remove or cut it.

Test drive the car carefully for a while, just to make sure everything is in good working order.

If your Corvette is now garaged full-time and not driven every day, this repair should last you well over 20 years before the hoses need replacing again.