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Fuel Tank (Gas Tank) Restoration

Step By Step Guide

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How to restore your gas (fuel) tank

In any major going over of the fuel system of a vehicle you need to take some time and evaluate the gas tank. Quite frequently the tank is in salvagable shape, but is filled with varnish, dirt, debris and other junk from years of use and abuse. As with all automotive work, disconnect the battery before starting in on the job.

The first step, obviously, is to remove the tank from the vehicle. Now, before you go ripping everything apart you need to try and ensure that there's no fuel in the tank, or if there is, then you have a means of dealing with it. Many old gas tanks have a threaded bolt, petcock, or other means of draining the tank. Now, I normally find these to be entirely usless because they've gummed/gooed/rusted in place, but it's always worth a try getting it out. Make sure to have a decent sized drain pan underneath to capture any gasoline that comes out. If it's not possible to remove it, or if your tank does not have one, then ensure you know where the fuel holes in the tank are so that you can pitch it at the correct angle when removing it.

I like to slide my jack under the fuel tank to support it while removing it. It will allow you to much better control the drop and removal when it's free from the vehicle. Disconnect the fuel fill, the fuel sender wiring and the fuel/fuel return lines. Remove the bolts that hold the tank in place and then slowly lower it to the ground. If there's still fuel in the tank, pour it off and set it aside. To safely dispose of the old gasoline let it evaporate away.

Go ahead and rinse the tank out with the garden hose. Watch for debris or rust coming out of the tank. Shine a flashlight inside to look at the interior. If you see a lot of rust you can dump some gravel or chain into the tank and shake it around. Just be careful as anything that might make a spark could cause an explosion. Rinse the tank out again. At this point you need to remove anything that isn't the tank itself. At a minimum this will be a fuel sender unit. At a maximum it may also include a fuel pump.

Now, for this project I've elected to use the Fuel Tank Restoration Kit from POR-15. It is a three-ish step process involving their cleaning product (Marine Clean), their metal etching product (Metal Ready) and the tank sealer (U.S. Standard Fuel Tank Sealer). I'm not specifically advertising the product here, it just happens to be what I like to use. There are other similar kits on the market. They work more or less the same with minor differences in the process.


Now, first step is to treat the interior of the tank with the Marine Clean. This stuff is somewhat dangerous, so don't get it on you, and wear rubber gloves. It'll get the varnish and gunk out of the tank as well as remove any leftover gasoline that may be in there. Tape off the holes in the tank with gaffing/duct tape. I prefer gaffing tape because it'll allow for hotter water during the cleaning process. Mix the cleaner 50/50 with hot water. Dump the mixture in the tank, seal off the final hole and shake it about. Make sure to turn the tank frequently to so that all of the interior surfaces are cleaned well. Pour off the solution into a bucket and then rinse the tank a couple times.

Now, the resealer kit instructions only cover the tank interior. Don't forget to take care of the exterior too! Once cleaned with marine clean go ahead and clean the exterior surfaces of the tank. Go over it first with a wire brush, then sand or sandblast it clean. If you are sandblasting make sure to tape over the openings to keep your media from getting inside the tank.


Now that the exterior is clean and you've had a chance to evaluate whether or not it has any holes or is beyond saving it's time to protect the exterior surface. I've elected to paint it with the POR-15 rust preventative paint. This will provide a great protective coating for the tank. We will put a final coat of Chassis coat on the exterior later. The POR-15 will take a bit to dry, and you need to absolutely ensure that it's fully cured before you proceed.


Now that the POR-15 has dried it's time to etch the interior of the tank. As before, tape off the the openings to the gas tank. Pour in the Metal ready and cap the final point. You need to ensure that every interior surface is treated with the Metal Ready. Rotate the tank every 10 to 20 minutes to give the solution an appropriate amount of time to etch very surface. Once done, drain it off and rinse the tank thoroughly with warm water.

Now, before we can apply the sealer (our final step on the interior of the tank) we have to ensure that the tank is totally dry. I stole the wife's hair dryer to dry the tank. Please note that the tank will heat up with hair dryer running inside. If it's particularly wet on the interior, you may need to allow the hair dryer to run in 20 minute intervals to keep from overheating the hair dryer. (If you break it, then the wife will kill you... fyi...)


When the tank has completely dried and cooled you can use the tank sealer. Open the tin and stir it fully so that it has a good uniform color. For the final time you'll need to tape off the tank openings. Pour the sealer in and slowly rotate the tank to ensure that all of the interior gets a good coating. If you were lucky enough to get the petcock off the tank, support the tank over the empty sealant tin and let it drain back. If you weren't so lucky drain it off as best you can. You want to get as much as possible of the extra salant out of the tank. The remaining sealant can then be dried and cured by adding som water to the can. Once it's hardened it's safe to put in the trash. While it drains make sure to chase any threaded parts on the gas tank. These may be things like the the point of attachment of the fuel sender unit and the fuel petcock. Because this stuff hardens so well if you don't chase the threads you may not get the screws back in. Now set the tank aside and give it time to dry and harden.

At this stage we've completed the internal treatment of the fuel tank. To finish the external treatment we will paint Chassis Coat over the POR-15 layer as the final protectant. POR-15, as strong as it is, is UV sensitive. While I don't expect to get a lot of light under the vehicle, it only makes sense to paint it with the final coat to protect it.

Once the Chassis Coat has dried the restoration is done. You just need to reassemble the tank and mount it on the vehicle!

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Contents copyright 2008, 2009 - Jody F. Kerr

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