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?
• Cylinder-cutout test on a multi-cylinder diesel to locate a misfiring cylinder • What you should feel/hear when you loosen (slacken) a high‑pressure fuel line on a cylinder that IS firing correctly • How air in a high‑pressure fuel line affects cylinder firing and how it might be cleared
• When you slacken the fuel line on a cylinder that is firing normally, what immediate change should happen to engine speed and smoothness? • If you slacken and then re‑tighten a line that had air in it, how could that action change the running condition of the engine afterward? • Based on the before-and-after behavior (rough before, no change while loosened, smooth after re‑tightening), which cylinder’s condition must have changed, and in what way?
• Compare engine behavior before, during, and after loosening the No. 5 line; list what changed and WHEN it changed • Ask yourself: during the time the No. 5 line was slack, was that cylinder contributing full power, partial power, or no power? • Decide whether the final smooth running indicates normal firing in all cylinders or a persistent misfire in the same cylinder as before.
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