🔍 Key Concepts

• Diesel fuel system flow path from the tank through filters, pumps, and injectors • Effects of water, dirt, or microbial growth in fuel on close‑tolerance components • Which engine systems rely on very fine clearances and clean fuel to function properly

💭 Think About

• Trace the path of contaminated fuel: which components does it physically pass through and contact first? • Ask which option involves parts with the smallest clearances and highest sensitivity to particles or water. • Consider which choices are more directly tied to fuel quality versus those mainly affected by air flow or lubrication.

✅ Before You Answer

• Verify which system (from the options) has high‑pressure, close‑tolerance parts that can easily plug, stick, or wear from dirty fuel. • Eliminate any answers that mainly relate to air intake temperature or lube oil cooling, which are usually influenced by other causes rather than fuel cleanliness. • Confirm that the remaining choice is the one whose normal operation most strongly depends on clean, properly filtered fuel.