You suspect that a diesel generator set on your river push boat 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 No. 5 fuel injector nozzle, the engine continues to run roughly as before with no real change. Upon re-tightening the high-pressure fuel line fitting, the engine begins and continues to run smoothly. What does this indicate?