Question 70 RVR05 - Master of LT 100 GRT

The Correct Answer is A **Why option A ("a defective ignition system") is correct:** If a gasoline engine turns over freely, it means the mechanical components (like the starter, crankshaft, pistons, and valve train) are operating smoothly and the engine is not mechanically seized or burdened by a heavy load. Since the engine is able to turn over, the issue is likely a lack of one of the essentials for combustion: air, fuel, or spark. In the absence of a strong spark (due to a defective ignition system, such as bad spark plugs, faulty coil, or bad wiring), the fuel-air mixture cannot be ignited, and the engine will crank continuously without starting. **Why the other options are incorrect:** * **B) too heavy a load:** If the load is too heavy, the engine would likely turn over slowly or not at all (it would fail to "turn over freely"). Since the engine *does* turn over freely, the load is not the primary cause of the no-start condition. * **C) low lube oil level:** Extremely low lube oil can cause catastrophic engine damage (seizing), which would prevent the engine from turning over freely. While a low oil level is dangerous, it does not typically prevent a *freely turning* engine from starting unless the engine has already failed catastrophically. Most no-start causes in a freely cranking engine relate to the air/fuel/spark triangle. * **D) weak valve springs:** Weak valve springs might cause performance issues (like engine misfire or reduced power) once the engine is running at high RPMs, but they are unlikely to prevent an engine that is turning over freely from starting altogether. A complete failure to start is more often related to the absence of spark or fuel delivery.