Any vehicle that sits for an extended period of time with gas in its tank will likely experience "gummed-up" gas -- that is, gas that eats away at the interior of the gas tank and thus loses its effectiveness. Gummed up gas can affect the vehicle's performance and fuel efficiency, among other issues. It can be removed, but will require detaching the gas tank.
Remove the gas tank from the main body of the engine. Depending upon the type of vehicle, this may require loosening bolts or screws and removing clamps holding the gas tank to any hoses. A bucket should be placed under the tank to catch any remaining liquid or "gummy" gas that flows out.
Cover the hole on the base of the gas tank with duct tape. This will ensure that any liquids used to clean the tank do not run out.
Pour in two cups water and two tablespoons of liquid dish soap.
Shake the contents vigorously to clean out the tank with the soapy water. Pour out the soapy water mixture and rinse out the tank with cool water.
Fill the empty gas tank halfway with warm water. Pour one half gallon of Muriatic acid, which can be purchased at hardware stores, into the tank. Wear rubber gloves, a mask and safety goggles when handling Muriatic acid.
Prop the tank up so that duct taped end is on the ground, and allow the Muriatic acid solution to sit for two hours.
Pour the Muriatic acid solution into a plastic bucket and rinse out the fuel tank three to four times with cool water.
Refill the gas tank with the appropriate fuel immediately, and reinstall it back onto the vehicle. Do not allow the gas tank to sit empty, as this can lead to rust formation.
