You suspect that a diesel generator set on your OSV has a misfiring cylinder because the engine, although warm, is running roughly. The six-cylinder engine is fitted with a multi-plunger in-line high pressure fuel injection pump with hydraulically operated injector nozzles. When you slacken the high pressure fuel line fitting at #3 fuel injector nozzle, the engine continues to run roughly as before with no real change. Upon re-tightening the high pressure fuel line fitting, there is no real change, as the engine continues to run roughly as before. What does this indicate?