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

A system for cleaning a fuel-injector that remains attached to an engine, the system comprising a source of fuel, a source of cleaning solution, a pump, and a control box configured to control operation of the pump, the system configured to:

• in a first configuration, supply the cleaning solution using the pump, such that the cleaning solution passes into, through, and out of the fuel-injector, without the cleaning solution passing into the engine, to thereby clean the fuel-injector;
• and
• in a second configuration, supply the fuel using the pump, such that the fuel passes into, through, and out of the fuel-injector, without the fuel passing into the engine, to thereby restore fuel flow through the fuel-injector,
• wherein, in the first configuration, a second fluid-valve is configured to supply the cleaning solution at a pressure that is below a threshold pressure which causes the fuel-injector to open fluid communication into the engine.