The fuel system business is booming. Aftermarket pumps, regulators, lines, fittings, tanks, injectors, fuel rails—even entire how-to books—revolve around the task of delivering more fuel to an engine.

You don't have to be Mr. Goodwrench to know that your car won't run without a steady supply of fuel, whether it runs on gasoline or diesel fuel. Less than three months ago, Honda recalled more than ...