on my 99 and both my 97s the fuel door is locking in that you can't open it from outside, it must be opened with the pull handle on the kick panel.

all of my monteros seemed to have stretched cables that wouldn't open the door for me. easy solution is to take a very small plastic cable tie and zip tie it on the end of the cable right next to the little ball in the fuel door mechanism. instead of the little ball catching the latch, the zip tie will take up some of the slack and in reality 'shorten' the cable.

worked like a charm, took me all of 1 minute and 37 seconds to complete.