Service engine light

Small leaks can be almost impossible to find visually. To handle this problem, they make a smoke machine that you can use to inject a white, non-toxic smoke under two pounds of pressure, then you watch for where it sneaks out. You might be able to find one of these at an auto parts store that rents or borrows tools. Good suspects are loose or missing hose clamps around the gas tank and charcoal canister, and a leaking purge valve for that canister.