How do you open the fuel door on a 1997 Corolla when the remote fuel-door release under the driver's seat does not open it?

This happened on my Corolla when the little spring lever popped out of the fuel cap. Just pull pack the carpet in the truck which lines the quarter panel just behind the fuel cap. You will see the release handle there. Be prepared to get weird looks from people when you open your trunk up after you pull up to the pumps.

open the trunk. remove the retainers that hold the carpet that goes all around the trunk (you might wanna start from the ones near the taillight). move the carpet aside so you can see the gas door from the inside. you will see the spring-loaded catch that locks the door. push it.

and in case the wire is not attached or torn, you may have to replace or reattach (if you are lucky) it. for replacement, get some brake wires of a mountain bike. and then get a mechanic to help you out with the rest.

Not sure if it applies to this model, but other Toyotas I've seen have a little spring clip that "pops" the door open once the latch is released. If the clip is gone, the lever releases the latch, but the door doesn't open up. You can easily pry it open with a knife (while an assistant lifts the lever). Use a bent piece of metal to fashion a replacement spring and glue it into place. It helps if you have another Toyota nearby to see how the thing is supposed to work. The dealer may have a part you can buy, if you don't have anything that will fit the bill.