Jeep Wrangler 20-Gallon Gas Tank Conversion

From 1991-1995, Chrysler offered two different sized gas tanks for the Jeep Wrangler: 15-gallon and 20-gallon. In reality, these two tanks were not different in size at all. The difference in some was a small plastic vent hose that extended down into the tank which prevented more than 15 gallons of fuel being filled into them. By shortening this hose, the tank can hold the 20 gallons of fuel it was originally made to carry. The entire conversion process is about a 60-90 minute job.

  1. Raise the vehicle on jack stands.
  2. Remove the   plastic   panel  in the rear right corner near the gas filler.
    This is held in place by four plastic rivets. Remove the rivets by securing the outer portion in place while prying the center outward 0.25″-0.5″ with a small screwdriver. The rivets will remove as whole pieces. Don’t damage them because you’ll need them for reassembly.
  3. Disconnect the fill vent hose from the tank.
    This is done by removing the hose clamp and pulling the hose off the fill vent neck. You may need to pry it, but it’s only held on with a hose clamp.
  4. Remove the inner plastic fuel vent neck liner.
    Inside the neck of the fuel vent hose, you can see a tube which lines the inside. This liner tube is made of hard plastic. Itýs about 9.75″ long and reaches about 7″ into the tank. Gas can not be filled beyond the bottom of this tube. Shortening it will increase the volume of gas that will fit into the tank. To remove it, you will need to pry it away from the sides with a small screwdriver and grab it with any small tool that offers a STRONG grip. I recommend a needle-nose vise grip because this tube is crammed in there TIGHT. In fact, removing this tube was the hardest task on this project. Some people removed this tube in sections by pulling out 3″, then cutting it off, and pulling another 3″ until the tube was completely removed.
  5. Cut a 2.5″ section from the liner tube.
    The fuel vent neck on the tank must have a section of the liner tube pressed back inside to maintain pressure applied when tightening the hose clamp (during re-assembly). I have no idea why this is, but since someone advised to do so, I didn’t argue. Cut a 2.25″-2.5″ section and fit it back into the fill vent neck. You’ll need a hammer or something heavy to pound it in. Make sure not to use a metal hammer should you be unlucky enough to strike something that causes sparks this close to the gas tank.
  6. Reassemble everything in the reverse order.
    Use the hose clamp to attach the fill vent hose to the fill vent neck, four rivets to reattach the  plastic  cover on the rear  panel , and five lug nuts to mount the removed wheel.

Unless you’ve installed a sending unit for a 20-gallon tank, the fuel gauge in the dashboard will be inaccurate. Others who have done this conversion claimed the gauge won’t begin to show movement until there is 15 gallons in the tank. This was not the case for me. My gauge doesn’t show movement until 10-12 gallons remain in the tank and when the gauge reads 1/2, the tank is near empty. It used to be empty when the gauge read 1/4, but I ran the tank near dry just to make certain and it is empty at the 1/2 mark. I don’t know if the sending arm got bent by this or what went wrong, but it’s now empty at 1/2.