🔍 Key Concepts

• Diesel fuel system operation – how fuel is delivered from tank to injectors • Effect of air bubbles in a liquid fuel system (loss of pressure, interruption of flow) • What conditions actually cause blue smoke, piston seizure, or corrosion in diesel engines

💭 Think About

• Think about what an injection pump and injector need in order to build up enough pressure for proper combustion. What happens if part of that fuel column is replaced by compressible air? • Which of the choices is a direct, immediate effect in the fuel system itself, rather than a long‑term or unrelated engine symptom? • For each wrong option, ask yourself: does air in the fuel line by itself realistically and quickly cause that result?

✅ Before You Answer

• Be clear on the difference between compressible air and incompressible liquid fuel in a high‑pressure line. • Check which listed problems are usually associated with lubrication failure/overheating versus combustion quality issues. • Verify in your diesel notes what symptom engineers are trying to remove when they say they need to bleed the fuel system after running out of fuel or opening the lines.