Across the U.S., the roar of gasoline-powered lawn mowers, leaf blowers, string trimmers, and other outdoor power tools is being replaced by the less punishing whir of their electric counterparts.

This is an easy one to troubleshoot. If it turns over but your mower won’t start, chances are you’ve got stale gasoline in the tank or the carburetor bowl. Gas goes stale after sitting for a while. So ...