Can most sour fruits be jelled by cooking with sugar?
Fruits that are high in pectin are not necessarily sour and sour fruits are not necessarily high in pectin. However, pectin is typically found in high concentrations in firm fleshed fruit such as apples and in the skins of citrus. Unripe fruit has even more than the ripe. So- I can see why you would come to that conclusion.

It is easy enough to find charts of pectin levels in various fruits. 

As you may notice many of these charts list not only fruits high in pectin but those high in acid. This is because acid is necessary to make pectin gel as it removes a charge on the pectin molecules that prevents them from tangling with each other. Low acid fruits, even if they are high in pectin, need extra acid for this reason.

If you are feeling all scientific about it, you can test pectin levels yourself.

There is no danger in experimenting. At least no danger of illness. You might end up with grainy jam if the pectin is too high or syrup if it is too low but it will all taste great.