The Fiat 124 Spider was built right up until 1979, when an upgraded model known as the Spider 2000 was introduced. All of the cars built through 1979 had a carburetor fuel system. After 1980, all of the Spider 2000s used a Bosch fuel injection.
The best part of the earlier cars is the simplicity of their fuel system. It basically consists of a fuel tank, mechanical fuel pump, filter and a carburetor. The only maintenance item is the fuel filter.
Depending on who has worked on the car before, this filter may be between the fuel tank and the fuel pump, or more likely between the fuel pump and the carburetor. The service interval should be about 10,000 miles to replace it, and as a good rule of thumb you can think of it being once every three times you change the engine oil.
Various brands and styles of fuel filter are available for the Fiat Spider. Because the carburetor system is a low-pressure system, the fuel filters are a universal design that is inexpensive and widely available. I like using the clear plastic ones that are about 2" long and have 5/16" inlet and outlet tubes. These clear plastic filters make it easy to see if fuel is flowing to the carburetor or if there are any contaminants in the fuel.
These plastic filters are available at any automotive parts store, many department stores, and of course on the internet. Many times I have gotten a great bargain at various car swap meets where many vendors will sell them 2-for-$5 or sometimes 5-for-$10. With prices like that, there's no reason to not replace the filters on schedule and even keep a spare in the glove box.
When it's time to change the filter, you can get the best results after the car sits overnight so that the gasoline will have drained back down out of the filter and you're less likely to get spills or any gas on your hand when you disconnect the fuel lines. The tools you will use are very simple: a flat-blade screwdriver and a pair of pliers. It is okay to do this inside your garage but leave the door open for good ventilation and absolutely no smoking or open flames around! You may want to wear a pair of protective gloves just because getting any gasoline on your hands produces, let us say, a "durable fragrance".
Release the hose clamp tension and slide it up the fuel line so that it is out of the way and less likely to get dropped and lost.
The rubber fuel line and the plastic filter pipes may have become slightly stuck together over time. Rather than use a straight pull to try to yank the filter off the fuel line, use a twisting motion you pull them apart. You may need a pair of pliers to help grip the fuel line, but be careful not to crush the plastic as it may slice the rubber line.
Write the mileage and date on the top of the filter as a reminder for the next service interval. When installing the new filter, use the same twisting motion to push it onto the fuel lines. Slide the clamp back up the rubber line and get it as close to the filter body as possible. This will make the best seal. Remember to push the car outdoors before trying to start it and check for leaks.
Also remember that it may take more than a minute of engine cranking to fill the filter and start the engine. It is better to run the starter in a series of short (15-20 second) attempts rather than trying to do it all in one long pitch.
Follow your shop manual and take care of your Fiat 124 Spider - because with this great weather, you've got Places to Go!!