I have a 1985 Jeep Laredo with the 20 gallon plastic tank. After a fill up, my dash gas gauge in the speedo reads WAY full and when driving around, it takes forever to move the needle--after I have driven around for the week, it starts to drop, but then faster than normal. When the gas gauge reaches 1/4 tank, the Jeep is empty and out of gas. For years, i have just filled it up before I get to a 1/4 tank, but my 15 year old boy is going to be driving it soon, so I want to fix it. Any ideas?