Cleaning, maintaining, refurbishing, and/or diagnosing engine components including fuel-injectors

A method of cleaning a fuel-injector while it remains attached to an engine assembly, the method comprising:

• coupling a source of cleaning solution to the fuel-injector,
• wherein the fuel-injector includes a first fluid-pathway that comprises:
• a first fluid-inlet,
• a first fluid-valve, and
• a first fluid-outlet, and
• wherein the fuel-injector further includes a second fluid-pathway that comprises:
• the first fluid-inlet,
• the first fluid-valve, and
• a second fluid-valve that controls fluid communication to a second fluid-outlet that communicates with combustion components of the attached engine assembly;
• operating the first fluid-valve to open the first fluid-pathway for the coupled source of cleaning solution;
• supplying the cleaning solution through the fuel-injector, such that the cleaning solution passes through the first fluid-pathway without passing through the second fluid-valve or the second fluid-outlet of the second fluid-pathway, wherein the second fluid-valve opens in response to being exposed to a first fluid pressure, and wherein the cleaning solution is supplied through the fuel-injector at a second fluid pressure that is less than the first fluid pressure, thereby cleaning the fuel injector;
• discontinuing the supplying of the cleaning solution through the first fluid-pathway of the fuel-injector;
• de-coupling the source of cleaning solution from the fuel-injector;
• and
• coupling a source of fuel to the fuel-injector.