Fuel Systems & Combustion Flashcards
6 cards from real Automotive and Mechanics practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Fuel Systems & Combustion flashcards as text
What is detonation (engine knock) caused by?
Answer: Fuel auto-igniting before the spark plug fires
Detonation occurs when the air-fuel mixture auto-ignites from heat and pressure before the spark plug fires, causing a damaging pressure spike.
Which fuel system test checks for injector leakage when the engine is off?
Answer: Leak-down (static leak) test
A static leak test measures fuel pressure drop with the pump off to determine if injectors are leaking fuel into the cylinders.
What is the role of the mass airflow (MAF) sensor in fuel management?
Answer: Measure the actual mass of air entering the engine for fuel calculation
The MAF sensor measures incoming air mass so the ECU can calculate the precise fuel quantity needed to achieve the target air-fuel ratio.
What does a vacuum leak do to the air-fuel mixture?
Answer: Leans the mixture by allowing unmetered air into the intake
A vacuum leak introduces unmetered air past the throttle body, leaning the mixture and causing rough idle, high idle, or lean misfire conditions.
Which type of fuel pump is used in modern high-pressure direct injection systems?
Answer: High-pressure mechanical pump driven by the camshaft
GDI systems use a cam-driven high-pressure mechanical pump to generate the 1,500–3,600 psi needed to inject fuel directly into the combustion chamber.
What is the effect of a clogged fuel filter on engine performance?
Answer: Causes fuel starvation, especially under load or at high RPM
A clogged fuel filter restricts flow, reducing fuel pressure and volume delivered to injectors, leading to lean conditions and power loss under load.