Mixed Deck — All EETC Topics Flashcards

How does a technician correctly set the ignition coil air gap on a small engine?

Answer: Use a wire feeler gauge between the coil armature legs and flywheel magnets while magnets are aligned

With the flywheel magnets aligned under the coil armature legs, a feeler gauge of the specified thickness is placed between them and the coil is tightened so it lightly grips the gauge.

What are the two benefits of a two-stroke engine design?

Answer: Lightweight and smaller size

Explanation: Two-stroke engines offer the benefits of lightweight construction and smaller size compared to their four-stroke counterparts. These characteristics make them desirable for applications where weight and space are significant considerations, such as handheld power tools, small recreational vehicles, and marine engines.

What symptom indicates a plugged or clogged cooling fin on an air-cooled engine?

Answer: Engine overheats and may shut down via thermal protection

Clogged cooling fins restrict airflow and heat dissipation, causing the engine to overheat and potentially trigger its thermal protection shutdown.

What symptom suggests ignition timing is too retarded (late) on a small engine?

Answer: Engine lacks power, runs hot, and has difficulty starting

Retarded ignition timing means combustion peaks too late in the power stroke, wasting energy as heat rather than pushing the piston, resulting in power loss and overheating.

In a piston-ported two-stroke engine, what two events occur simultaneously as the piston moves from Bottom Dead Center (BDC) to Top Dead Center (TDC)?

Answer: Intake (into crankcase) and compression

As the piston travels upward from BDC to TDC, it creates a low-pressure area in the sealed crankcase, drawing the fresh air-fuel mixture in through the intake port. At the same time, the piston is compressing the air-fuel mixture that was previously transferred into the cylinder.

Which of the following is a critical first step when diagnosing a 'crank, no start' condition on a modern compact diesel engine?

Answer: Checking for diagnostic trouble codes (DTCs) with a scan tool.

Modern diesel engines are heavily controlled by an Engine Control Module (ECM). Scanning for DTCs should be the first step, as a fault code can quickly direct the technician to the specific system (e.g., fuel pressure, sensor input, glow plug circuit) that is preventing the engine from starting, saving significant diagnostic time.

During the intake stroke in a four-stroke engine, what are the positions of the valves?

Answer: The intake valve is open and the exhaust valve is closed

Explanation: During the intake stroke of a four-stroke engine, the intake valve is open to allow the entry of air-fuel mixture into the cylinder from the intake manifold. Simultaneously, the exhaust valve remains closed to prevent any exhaust gases from escaping. This configuration ensures that a fresh air-fuel mixture is drawn into the cylinder for combustion during the subsequent compression stroke.

Which coolant additive prevents corrosion and scale buildup in liquid-cooled engine passages?

Answer: Corrosion inhibitor package in antifreeze

Modern antifreeze formulations include a corrosion inhibitor package that protects metal surfaces and prevents scale deposits in cooling passages.

What is the effect of air in a liquid-cooled engine's cooling system?

Answer: Creates hot spots and reduces cooling efficiency by forming air pockets

Air pockets in the cooling system do not transfer heat as efficiently as liquid coolant, creating localized hot spots that can damage engine components.

What does the kill switch (stop switch) on a small engine do to stop the engine?

Answer: Grounds the ignition coil primary circuit to prevent spark

The kill switch grounds the ignition coil's primary winding, which prevents the voltage collapse needed to produce a spark, stopping combustion and shutting the engine down.

When diagnosing the cause of a bent crankshaft on a lawnmower, which of the following is the most common cause?

Answer: Impact with an immovable object like a rock or tree stump

A bent crankshaft is most often caused by a sudden, forceful stop of the rotating blade assembly. When the blade strikes an immovable object, the rotational inertia is transferred directly to the crankshaft, which can bend under the extreme force.

A piece of equipment that was stored for several months with E10 gasoline in the tank now fails to start. The fuel lines appear swollen and soft, and the carburetor is clogged with a gel-like substance. Which of the following is the most likely cause of these issues?

Answer: Phase separation and water absorption by the ethanol

Ethanol is hygroscopic, meaning it absorbs water from the atmosphere. Over time, it can absorb enough water to cause "phase separation," where the ethanol/water mixture separates from the gasoline and sinks. This mixture can corrode metal parts, degrade rubber/plastic fuel lines, and form gums/gels that clog fuel passages.

A technician hears a high-pitched whining or a sound like marbles rattling inside a hydraulic pump. The suction line filter is found to be severely clogged. This noise is most likely caused by:

Answer: Cavitation

Cavitation is the formation and rapid collapse of vapor bubbles in a liquid when the pressure drops below the fluid's vapor pressure. A clogged suction filter restricts flow to the pump, causing a significant pressure drop at the inlet, which leads to cavitation. The noise is created by the shockwaves from the imploding bubbles.

Which of the following factors may affect the operating temperature of an air-cooled engine?

Answer: All of the above

Explanation: All of the listed factors—engine oil quality/quantity, spark plug heat range, and carburetor jetting—can influence the operating temperature of an air-cooled engine. Engine oil quality and quantity affect lubrication and cooling, while the spark plug heat range determines the temperature at which the spark plug operates, impacting combustion and engine heat. Similarly, carburetor jetting affects fuel mixture and combustion, which can influence engine temperature. Therefore, all these factors collectively contribute to the overall operating temperature of an air-cooled engine.

In what positions can a two-stroke leaf blower operate effectively?

Answer: Any position

Explanation: Two-stroke leaf blowers can operate effectively in any position due to their simple lubrication system, which does not rely on a sump and oil pump like four-stroke engines. This allows for flexibility in operation, making them suitable for various angles and orientations during use.

What is the air gap specification between the ignition coil armature and flywheel magnets used for?

Answer: Setting the magnetic coupling distance for proper coil charging and spark energy

The air gap between the coil armature and flywheel magnets controls how strongly the magnets induce current in the coil, directly affecting spark energy output.

Why is it important to use the spark plug type and heat range specified by the engine manufacturer?

Answer: Using the wrong heat range can cause fouling, pre-ignition, or engine damage

The manufacturer's specified plug heat range is matched to the engine's combustion temperature profile; a wrong heat range causes either fouling from a too-cold plug or pre-ignition from a too-hot plug.

Which condition causes a liquid-cooled engine to run consistently cool and never reach operating temperature?

Answer: Thermostat stuck in the open position

A thermostat stuck open allows continuous coolant flow through the radiator, preventing the engine from building up heat to reach its operating temperature.

Which of the following best describes the function of a Ground Fault Circuit Interrupter (GFCI) receptacle on a portable generator?

Answer: It protects the user from electric shock by detecting small imbalances in current flow.

A GFCI is a safety device designed to protect people. It constantly monitors the current flowing on the hot and neutral wires. If it detects a small imbalance (as little as 4-6 milliamps), it assumes the current is leaking to ground (potentially through a person) and trips the circuit in a fraction of a second to prevent a serious shock. It does not protect against overloads or short circuits.

An engine overheats only under heavy load but runs normal at idle. Which cooling system component is most likely faulty?

Answer: Partially clogged radiator or fins reducing capacity under high heat output

A partially restricted cooling system has enough capacity for light-load heat rejection but is overwhelmed during heavy-load conditions when heat output is greatest.