When purchasing a vehicle that has sat for a long period of time, there are multiple maintenance tasks that must be performed before you can drive it. One is cleaning out the fuel tank. Any gas left behind since the last time the car was driven will have formed a sticky, caramel like varnish on the inside of the tank that can be particularly difficult to clean. Having the tank professionally cleaned can be burdensome and expensive. With a little preparation and planning, you can clean the tank yourself instead.
Dress in old clothing, making sure your arms are covered completely. Put on protective eye wear and rubber gloves.
Move the tank to a well-ventilated area. Outdoors is strongly preferred. If you are concerned about the grass then this process should also be completed in an area where there is no grass or the grass has already died.
Put enough tap water in the tank so that you can easily slosh it around. About a quarter of the way full is sufficient. It is essential to add the water first to avoid splashing the acid or releasing undesirable vapors that can burn your internal organs when inhaled.
Add 1 cup of muriatic acid to the tank. Let the mixture set for one minute.
Slosh the mixture around in the tank to make contact with any areas not already under the water. Slosh for one to two minutes.
Dump the tank and repeat the process as many times as necessary to remove the sludge. When the water is mostly clear as it is dumped, proceed to the next step.
Fill the tank half way with water.
Add 1/2 gallon of acid then fill the tank the rest of the way with more water.
Shake the tank slightly to move the contents around and then let sit overnight.
Dump the contents out. Seal the tank with tank sealer to avoid oxidation of the newly cleaned metal.
