🔍 Key Concepts

• Diesel fuel injection systems and how they rely on solid (non-compressible) fuel to build pressure • What happens when air, which is compressible, is present instead of solid fuel in a high‑pressure line • The basic requirements for a diesel engine to start: compression, fuel, and timing

💭 Think About

• Ask yourself what introducing a compressible gas (air) into a line designed for high‑pressure liquid fuel will do to injection timing and quantity. • Consider which option best matches a condition where the injectors are not receiving properly pressurized fuel at the right instant. • Think about normal diesel starting problems: when cranking speed and compression are good, what fuel‑system issue most commonly prevents the engine from firing at all?

✅ Before You Answer

• Verify which choice directly relates to fuel not being injected correctly into the cylinders. • Eliminate any options that mainly involve engine overspeed or changes to mechanical compression ratio, since those are separate phenomena. • Check which answer describes a typical symptom seen after you have opened the fuel system and not bled the lines properly.