You suspect that a diesel generator set on your ocean-going tug has a faulty unit injector because the engine, although warm, is running roughly. The two-stroke six-cylinder engine is fitted with mechanically operated unit injectors. When you push and hold down the injector follower of the No. 4 unit injector, the engine runs even rougher than before. What does this indicate?
• Unit injector cut-out test on a multi-cylinder diesel engine • Effect on engine roughness when you disable a good cylinder versus a faulty cylinder • Relationship between one cylinder’s condition and how the overall engine smoothness changes when that cylinder is taken out of operation
• When you hold down the injector follower on one cylinder, what are you essentially doing to that cylinder’s fuel delivery? • If the engine runs even rougher after you disable that cylinder, what does that say about how well that cylinder was contributing before you touched it? • If only ONE cylinder were faulty, what would you expect to feel as you test each cylinder one by one with the follower? What would you feel when you finally get to the bad one?
• Be clear on what pushing and holding down the injector follower does to fuel injection in that cylinder. • Compare engine behavior when you disable a healthy cylinder versus when you disable the already-faulty cylinder. • Confirm whether the test result points to No. 4 being the bad cylinder, or to No. 4 being good and some other cylinder being the problem.
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