🔍 Key Concepts

• Fuel injector spray pattern and how it affects combustion in a diesel engine • Difference between idling and under-load operation in terms of fuel quantity and air use • What happens when fuel droplets are too large or poorly atomized

💭 Think About

• If spray holes are plugged, how does that change the way fuel enters the cylinder (fine mist vs large droplets)? • Would that kind of problem be more noticeable only at idle, only under load, or at both conditions? Why? • Which option describes a symptom that has the same root cause as poor atomization: incomplete burning or abnormal ignition timing?

✅ Before You Answer

• Identify which choices describe abnormal ignition timing (detonation/preignition) versus poor combustion/incomplete burn (smoke). • Ask: does a partially plugged injector usually change when fuel ignites, or how completely it burns? • Match the additional symptom to the same basic problem already given in the question: excessive smoking at idling speed.