List three common indicators of fuel system trouble.

• A. Unstable fuel pressure, but not fuel flow changes.
• B. Abnormal fuel flow only.
• C. Unstable fuel pressure, abnormal fuel flow, and fuel leaks or inconsistent spray patterns.
• D. Engine vibration only during idle.

Answer: (C)

A common signal of trouble in a fuel system is when multiple symptoms show up together, because fuel delivery relies on stable pressure, consistent flow, and proper atomization. Unstable fuel pressure means the system can’t hold a steady pressure, which disrupts how much fuel is available at the injectors or metering device and leads to timing and fuel-air mixture variations. Abnormal fuel flow points to changes in the amount or rate of fuel reaching the engine, often caused by restrictions, leaks, or pump/regulator issues. Fuel leaks or inconsistent spray patterns indicate a physical fault in lines, seals, or injectors, causing leaks or irregular atomization, which directly corrupts combustion quality. When these indicators appear together, they provide a clearer picture of fuel system problems you need to inspect, such as the pump, regulators, filters, lines, and injectors.

Other options miss one or more key signs. Focusing on unstable pressure alone without considering flow changes or leaks ignores a critical part of how the system operates. Abnormal flow by itself doesn’t capture pressure stability or physical leakage/atomization issues. Engine vibration during idle is a broad symptom that can arise from many non-fuel-system causes, and it doesn’t specifically point to fuel-delivery problems.