I just purchased a 1997 Contour 4 cyl with a GFI Compressed Natural Gas dual fuel system. It was sold as "not switching to Natural Gas" i.e. it only runs on gasoline. I have my own CNG fueling station and currently drive one Ford Crown Victoria natural gas car. Does someone have diagnostic information on this GFI system? Since I am asking beginner questions, when does the timing belt need to be changed? This car has 130,000 miles, but was supposed to have been "fleet maintained" by a reputable government agency. (some are quite reliable when spending taxpayer money)

Welcome!

I don't know anything about natural gas vehicles, but the timing belt is usually changed between 60k and 90k.
If you get it replaced, the mechanic will usually advise you to change the tensioner pulleys too since they won't charge you more for the labor (as opposed to opening it up again)

at 130k I would say its time. the belts normally don't wear alot, it the pullies you have to worry about.