🔍 Key Concepts

• Diesel engine runaway/overspeed on startup and what uncontrolled fuel sources can cause it • How faulty fuel system components (like injectors) affect engine speed and fuel delivery • How external or unintended fuel sources (e.g., lube oil past turbo seals, airborne hydrocarbons) can enter the intake and act as fuel

💭 Think About

• Think about what an engine actually needs in excess to overspeed on startup: is it air, fuel, or load that changes the most suddenly? • For each option, ask: could this condition provide extra, uncontrolled fuel or fuel-like vapor to the engine right when it starts? • Consider whether any of the listed conditions could independently cause overspeed, and whether some of them describe similar underlying problems.

✅ Before You Answer

• For each choice, decide if it can realistically lead to uncontrolled additional fuel entering cylinders at startup. • Ask whether turbocharger seal ring failure can let lube oil or fuel into the intake side, and whether that can burn like fuel. • Consider if airborne hydrocarbons in the engine room air could be drawn into the intake and act as fuel during startup.