EETC Technician Certification Exam — Questions and Answers

Question 1: In a multi-grade engine oil designation like "SAE 10W-30," what does the "W" stand for?

Water-resistant
Winter (Correct answer)
Wear-protection
Weight

Correct answer: Winter

The "W" stands for "Winter" and indicates the oil's viscosity (flow characteristics) at colder temperatures. The first number (10) represents its viscosity when cold, while the second number (30) represents its viscosity at the engine's normal operating temperature.

Question 2: A customer's small engine will not start. A compression test reveals a reading of 40 PSI, which is significantly below the manufacturer's specification. Performing a 'wet' compression test, where a small amount of oil is added to the cylinder, results in the compression reading increasing to 95 PSI. What is the most likely cause of the low compression?

A cracked cylinder head
A stuck open intake valve
A blown head gasket
Worn piston rings (Correct answer)

Correct answer: Worn piston rings

When oil is added to the cylinder, it temporarily creates a better seal between the piston rings and the cylinder wall. A significant increase in compression during a wet test indicates that the piston rings are worn and are the source of the compression loss.

Question 3: What is the stoichiometric (ideal) air-to-fuel ratio for gasoline combustion?

14.7:1 (Correct answer)
8:1
10:1
20:1

Correct answer: 14.7:1

A 14.7:1 ratio provides just enough air to completely burn all the fuel, minimizing unburned hydrocarbons and emissions.

Question 4: While testing an electronic ignition coil with a multimeter set to ohms, a technician measures the resistance of the secondary winding. What would a reading of 'OL' or infinity most likely indicate?

There is an open circuit or break within the secondary winding. (Correct answer)
The secondary winding has an internal short circuit.
The coil is functioning correctly within specifications.
The primary winding is shorted to ground.

Correct answer: There is an open circuit or break within the secondary winding.

The secondary winding is a very long, fine wire. A reading of 'OL' (Over Limit) or infinity indicates infinite resistance, meaning there is a break in the winding and the circuit is open. A short circuit would show as a very low resistance reading, not an open one.

Question 5: On equipment with an electronic ignition module, what common failure symptom occurs when the module overheats?

Engine runs fine when cold but dies after reaching operating temperature and restarts after cooling down (Correct answer)
Battery drains overnight
Engine runs rough only at idle
Engine surges at full throttle only

Correct answer: Engine runs fine when cold but dies after reaching operating temperature and restarts after cooling down

A failing electronic ignition module often breaks down electrically when hot, causing the engine to run normally when cold, die after warming up, and restart only after the module cools.

Question 6: A technician is servicing a compact diesel engine equipped with a Diesel Particulate Filter (DPF). The operator reports frequent DPF warning lights and poor performance, primarily during low-speed, stop-and-go operation. What is the most likely reason for these symptoms?

A cracked exhaust manifold.
Failure of the passive regeneration process. (Correct answer)
The engine oil is of the wrong viscosity.
The fuel's cetane rating is too high.

Correct answer: Failure of the passive regeneration process.

Passive regeneration requires high exhaust temperatures, typically achieved during highway driving or high-load conditions, to burn off soot. In low-speed, stop-and-go operation, the exhaust temperature is often too low for passive regeneration to occur effectively, leading to soot accumulation and the triggering of active or forced regeneration cycles and warning lights.

Question 7: What is the primary function of a carburetor in a small engine?

To regulate oil pressure throughout the engine
To generate electrical current for the ignition system
To mix air and fuel in the correct ratio for combustion (Correct answer)
To cool the engine during operation

Correct answer: To mix air and fuel in the correct ratio for combustion

The carburetor mixes air and fuel in the proper ratio so the mixture can ignite and combust efficiently in the cylinder.

Question 8: A customer complains their chainsaw, a two-stroke engine, is producing excessive blue smoke and has a fouled spark plug. Which of the following is the most likely cause?

Worn piston rings causing oil to leak from a sump
An incorrect fuel-to-oil ratio (too much oil) (Correct answer)
A malfunctioning ignition coil
A clogged air filter causing a lean mixture

Correct answer: An incorrect fuel-to-oil ratio (too much oil)

In a two-stroke engine, lubrication is provided by oil mixed with the gasoline. An incorrect, overly rich oil mixture will not burn completely, leading to excessive blue smoke and oily carbon deposits on the spark plug.

Question 9: Which type of hydraulic pump is generally more tolerant of contamination, has a simpler design, and is typically lower in cost, but is only available as a fixed displacement unit?

Vane pump
Gear pump (Correct answer)
Axial piston pump
Radial piston pump

Correct answer: Gear pump

Gear pumps are known for their ruggedness, simple design with few moving parts, and lower cost compared to piston pumps. While piston pumps offer variable displacement and higher pressure capabilities, gear pumps are fixed displacement and are more tolerant of fluid contamination.

Question 10: What is the primary principle that allows a carburetor's venturi to draw fuel from the float bowl into the intake airstream?

The Coandă Effect
Archimedes' Principle
Bernoulli's Principle (Correct answer)
Pascal's Law

Correct answer: Bernoulli's Principle

Bernoulli's Principle states that as the velocity of a fluid (air) increases, its pressure decreases. The venturi is a restriction in the carburetor throat that forces air to speed up, creating a low-pressure area that siphons fuel from the higher-pressure float bowl.

Question 11: What is the most common type of valve used in a two-stroke engine?

Rotary valve
Reed valve (Correct answer)
Sleeve valve
Poppet valve

Correct answer: Reed valve

Explanation: The most common type of valve used in a two-stroke engine is the reed valve. Reed valves are thin, flexible plates typically made of metal or composite materials. They are positioned between the carburetor and the crankcase intake port and function to control the flow of air-fuel mixture into the engine. Reed valves are preferred in two-stroke engines due to their simplicity, reliability, and effectiveness in optimizing engine performance.

Question 12: Which of the following is a critical first step when diagnosing a 'crank, no start' condition on a modern compact diesel engine?

Immediately performing an engine compression test.
Testing the output of the starter motor.
Replacing the fuel filter and bleeding the system.
Checking for diagnostic trouble codes (DTCs) with a scan tool. (Correct answer)

Correct 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.

Question 13: A technician is diagnosing an engine that starts easily when cold but stalls after 5-10 minutes of operation. Once it stalls, it cannot be restarted until it has cooled down for a significant period. What is the MOST likely cause of this issue?

Clogged fuel filter
Faulty ignition coil (Correct answer)
Incorrect valve lash
Worn piston rings

Correct answer: Faulty ignition coil

Ignition coils can develop internal shorts that only manifest when the component heats up and its internal windings expand. This creates an open circuit, killing the spark. As the coil cools, the connection is restored, allowing the engine to start again. A clogged fuel filter would likely cause issues under load, not consistently after a specific runtime. Worn rings and incorrect valve lash would cause consistent problems like low power or hard starting, regardless of temperature.

Question 14: 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:

Detonation
Cavitation (Correct answer)
Aeration
Vibration

Correct 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.

Question 15: What is the correct initial starting position for a typical carburetor mixture screw before fine-tuning?

3 turns out from lightly seated
Fully open to maximum travel
1 to 1.5 turns out from lightly seated (Correct answer)
Fully closed (seated) with zero turns out

Correct answer: 1 to 1.5 turns out from lightly seated

Starting at 1–1.5 turns out from lightly seated provides a safe baseline mixture that allows the engine to start for final adjustment.

Question 16: What is the most likely cause of a broken compression ring in a four-stroke engine?

Valve timing issues
Overheating
Poor lubrication
Detonation (Correct answer)

Correct answer: Detonation

Explanation: Detonation, also known as engine knock, is the most likely cause of a broken compression ring in a four-stroke engine. Detonation occurs when the air/fuel mixture ignites prematurely or unevenly in the combustion chamber, leading to a rapid increase in pressure that can cause mechanical damage, including broken piston rings. Addressing detonation issues through proper fuel quality, ignition timing, and engine tuning is essential to prevent such damage in four-stroke engines.

Question 17: What type of coolant is recommended for aluminum engine components in modern small engines?

Traditional green IAT coolant
OAT or HOAT coolant designed for aluminum protection (Correct answer)
ATF fluid
Plain distilled water

Correct answer: OAT or HOAT coolant designed for aluminum protection

Organic Acid Technology (OAT) or Hybrid OAT (HOAT) coolants contain additives specifically formulated to protect aluminum from corrosion, which is critical for modern aluminum engine components.

Question 18: A technician measures the output of a North American standard mobile generator and finds the frequency is stable at 62.5 Hz with no load connected. What is the most likely cause for this reading?

The stator has a shorted winding.
The engine speed is set slightly too high. (Correct answer)
The main circuit breaker is faulty.
The Automatic Voltage Regulator (AVR) is malfunctioning.

Correct answer: The engine speed is set slightly too high.

The output frequency of a generator is directly proportional to the engine's speed (RPM). For a standard 60 Hz output in North America, the engine must run at 3600 RPM. A frequency of 62.5 Hz indicates the engine is running slightly faster than required. This is often a deliberate setting (no-load droop) to ensure the frequency remains within an acceptable range once a load is applied.

Question 19: Why do two-stroke engines generally cost less to manufacture compared to four-stroke engines?

They operate more efficiently
They have fewer parts (Correct answer)
They are made from cheaper materials
They require less precision in manufacturing

Correct answer: They have fewer parts

Explanation: Two-stroke engines cost less to manufacture primarily because they have a simpler design with fewer parts compared to four-stroke engines. This simplicity reduces the complexity of the manufacturing process, leading to lower production costs.

Question 20: What causes a cooling fan shroud to be critical on an air-cooled engine?

It directs airflow over all cylinder fins evenly to prevent hot spots (Correct answer)
It seals the crankcase from external debris
It supports the fuel tank
It reduces engine noise only

Correct answer: It directs airflow over all cylinder fins evenly to prevent hot spots

The shroud channels and directs air from the flywheel fan uniformly over all cylinder and head fins, preventing localized overheating or hot spots.

Question 21: What symptom indicates a plugged or clogged cooling fin on an air-cooled engine?

Engine RPM surges at idle
Engine runs rich
Engine produces black smoke
Engine overheats and may shut down via thermal protection (Correct answer)

Correct 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.

Question 22: A contractor wants to power a 13-amp circular saw (running watts: 1560W, starting watts: 2500W) and a 10-amp air compressor (running watts: 1200W, starting watts: 2000W) with a generator rated for 4000 running watts and 5000 surge (starting) watts. Which statement is correct?

The total running watts exceed the generator's rated capacity.
The generator can run both tools but cannot start them simultaneously. (Correct answer)
The generator can start either tool individually but cannot run both at the same time.
The generator can start and run both tools without any issues.

Correct answer: The generator can run both tools but cannot start them simultaneously.

The total running watts (1560W + 1200W = 2760W) is well below the 4000W rating. However, the combined starting watts if both tools start at the exact same moment (2500W + 2000W = 4500W) is below the 5000W surge rating. The most common and correct method for calculation is to take the total running watts (2760W) and add the single highest starting watts (2500W), which equals 5260W. This exceeds the 5000W surge capacity. Therefore, the generator can run both tools, but attempting to start them at the same time will overload it.

Question 23: What is cavitation in a liquid-cooled engine water pump?

Pump impeller spinning in reverse
Air being trapped in the cooling jacket
Formation and collapse of vapor bubbles that erode pump surfaces (Correct answer)
Coolant overheating due to blocked passages

Correct answer: Formation and collapse of vapor bubbles that erode pump surfaces

Cavitation occurs when low pressure causes coolant to vaporize, forming bubbles that collapse violently and erode the pump impeller and housing.

Question 24: Which type of bearing is best suited for applications with high radial loads in a compact space, such as in the connecting rod or as crankshaft main bearings in some small engines?

Plain sleeve bearings without rolling elements
Thrust ball bearings
Magnetic bearings
Needle roller bearings (Correct answer)

Correct answer: Needle roller bearings

Needle roller bearings use long, thin cylindrical rollers. This design distributes the load over a larger surface area, allowing them to handle high radial loads within a small, compact housing, making them ideal for applications like connecting rod ends and transmissions where space is limited.

Question 25: Which of the following components in a small engine's charging system is specifically designed to act as a voltage regulator by allowing current to flow in reverse once a specific voltage is reached?

Rectifier Diode
Zener Diode (Correct answer)
Stator
Capacitor

Correct answer: Zener Diode

A Zener diode is a special type of diode designed to operate in the reverse-biased condition. When the voltage across it reaches the 'Zener voltage,' it conducts in reverse, effectively shunting excess voltage to ground. This characteristic allows it to be used as a simple and effective voltage regulator in small engine charging circuits.

Question 26: In a hydraulic system, what is the primary function of a relief valve?

To regulate the speed of hydraulic motors.
To cool the hydraulic fluid as it returns to the reservoir.
To limit the maximum pressure within the system. (Correct answer)
To filter contaminants from the hydraulic fluid.

Correct answer: To limit the maximum pressure within the system.

A hydraulic relief valve is a critical safety component designed to protect the system from over-pressurization. When the system pressure exceeds a preset limit, the relief valve opens, diverting excess fluid back to the reservoir, thereby preventing damage to pumps, hoses, and other components.

Question 27: In a splash lubrication system, how is oil primarily distributed to the various moving parts of the engine?

The fuel/oil mixture lubricates the components.
A dipper on the connecting rod splashes oil from the sump. (Correct answer)
Gravity feeds oil from a reservoir above the engine.
A high-pressure pump forces oil through galleries.

Correct answer: A dipper on the connecting rod splashes oil from the sump.

In a splash lubrication system, a dipper or slinger attached to the bottom of the connecting rod cap scoops up oil from the crankcase sump with each rotation of the crankshaft. This action splashes and throws oil onto the cylinder walls, bearings, and other moving parts.

Question 28: During which phase of the four-stroke cycle are both the intake and exhaust valves momentarily open at the same time?

Intake stroke
Power stroke
Valve overlap (Correct answer)
Compression stroke

Correct answer: Valve overlap

Valve overlap is the period at the end of the exhaust stroke and the beginning of the intake stroke where both valves are open. This process uses the momentum of the exiting exhaust gases to help draw the new fuel/air mixture into the cylinder, improving engine efficiency at higher RPMs.

Question 29: In a typical two-stroke engine's port timing sequence, which port is the first to open as the piston moves downward on the power stroke?

The boost port
The transfer port
The intake port
The exhaust port (Correct answer)

Correct answer: The exhaust port

The exhaust port must open first on the downstroke to release the high-pressure exhaust gases. This process, called 'blowdown', lowers the cylinder pressure enough so that when the transfer ports open shortly after, the fresh charge can effectively enter the cylinder and scavenge the remaining exhaust without being blown back into the crankcase.

Question 30: How many camshaft revolutions are equivalent to one revolution of the crankshaft in a four-stroke engine?

Two
Half (Correct answer)
Double
One

Correct answer: Half

Explanation: In a four-stroke engine, the camshaft revolves at half the speed of the crankshaft. This means that for every one revolution of the crankshaft, the camshaft completes half a revolution. This timing relationship ensures that the intake and exhaust valves are actuated at the appropriate times during the engine cycle.

Question 31: When using a multimeter to test the resistance of a glow plug, what would a reading of 'OL' (Over Limit) or infinity most likely indicate?

The glow plug is functioning correctly.
A short circuit to ground.
The engine block is not properly grounded.
An open circuit within the glow plug element. (Correct answer)

Correct answer: An open circuit within the glow plug element.

A reading of 'OL' or infinity on a multimeter set to measure resistance (Ohms) indicates an open circuit. In the context of a glow plug, this means the internal heating element is broken and cannot complete the electrical circuit, rendering it inoperative.

Question 32: What does a black, sooty spark plug indicate about engine combustion?

Ignition timing is too advanced
Lean fuel mixture
Correct air-fuel ratio
Rich fuel mixture or oil fouling (Correct answer)

Correct answer: Rich fuel mixture or oil fouling

Black, sooty deposits on a spark plug indicate excess unburned carbon from a rich fuel mixture or oil entering the combustion chamber.

Question 33: What symptom suggests ignition timing is too retarded (late) on a small engine?

Engine knocks and detonates under load
Engine lacks power, runs hot, and has difficulty starting (Correct answer)
Engine overspeeds uncontrollably
Engine runs smoothly at all speeds

Correct 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.

Question 34: 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)?

Exhaust and intake (into crankcase)
Intake (into crankcase) and compression (Correct answer)
Power and exhaust
Scavenging and intake (into cylinder)

Correct 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.

Question 35: A customer's zero-turn mower clicks once when the key is turned to the start position, but the engine does not crank. The battery is fully charged and the connections are clean and tight. Which of the following is the MOST likely cause?

A seized engine.
A clogged fuel filter.
A faulty starter solenoid. (Correct answer)
An open in the primary ignition coil winding.

Correct answer: A faulty starter solenoid.

The single click indicates that the starter solenoid is being energized (receiving power from the key switch) but is failing to make the high-current connection to power the starter motor itself. This can be due to burnt internal contacts or a mechanical failure within the solenoid. A seized engine would typically result in a loud 'thud' and no crank, while ignition and fuel issues would allow the engine to crank but not start.

Question 36: Which stroke follows the exhaust stroke in a four-stroke engine?

Compression
Expansion
Intake (Correct answer)
Power

Correct answer: Intake

Explanation: In a four-stroke engine, the intake stroke follows the exhaust stroke. After the exhaust stroke, the intake valve opens, allowing the piston to move downwards and draw in a fresh air-fuel mixture from the intake manifold into the cylinder during the intake stroke. This cycle ensures the continuous operation of the engine.

Question 37: What is the primary function of the flyweights within a mechanical governor system on a small engine?

To sense changes in engine speed (RPM) (Correct answer)
To advance the ignition timing as engine speed increases
To counterbalance the crankshaft for smoother operation
To splash lubricate the internal engine components

Correct answer: To sense changes in engine speed (RPM)

As the engine speed increases, centrifugal force causes the flyweights to move outward. This movement is transferred through a linkage to the carburetor's throttle plate to maintain a set speed. When the engine slows under load, the flyweights move inward, opening the throttle. Their movement directly corresponds to engine RPM, allowing the system to sense and react to speed changes.

Question 38: What is the correct method for verifying carburetor adjustment after making changes?

Test performance at idle, mid-range, and full throttle under actual load (Correct answer)
Check the color of fuel remaining in the bowl after shutdown
Run the engine at idle for 30 seconds and listen for smoothness
Rev the engine to full throttle briefly with no load attached

Correct answer: Test performance at idle, mid-range, and full throttle under actual load

Each throttle range uses a different carburetor circuit, so adjustment must be verified across all operating conditions to confirm proper tuning.

Question 39: In a final drive that uses a planetary gear set, what is the primary purpose of this arrangement?

To allow for quick changes in the direction of rotation.
To act as a hydraulic clutch between the motor and the axle.
To provide significant torque multiplication and speed reduction. (Correct answer)
To increase the output speed while decreasing torque.

Correct answer: To provide significant torque multiplication and speed reduction.

Planetary gear sets are used in drivelines and final drives to achieve significant speed reduction in a compact space. This reduction in speed results in a proportional increase in output torque, which is essential for driving wheels or tracks on equipment.

Question 40: 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?

Phase separation and water absorption by the ethanol (Correct answer)
Varnish buildup from non-ethanol gasoline
The fuel's octane rating being too low for the engine
An incorrect two-stroke oil mixture in the fuel

Correct 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.

Question 41: What are the two disadvantages of a two-stroke engine?

Reduced fuel efficiency and shorter lifespan
Higher maintenance costs and lower power output
Limited torque and larger size
More noise and greater emissions (Correct answer)

Correct answer: More noise and greater emissions

Explanation: Two-stroke engines are known for producing more noise and emitting greater levels of pollutants compared to four-stroke engines. These factors can be drawbacks in applications where noise pollution and environmental concerns are significant considerations.

Question 42: Which of the following factors may affect the operating temperature of an air-cooled engine?

Carburetor jetting
Engine oil quality/quantity
All of the above (Correct answer)
Spark plug heat range

Correct 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.

Question 43: An engine has good compression and fuel but will not start. A spark test shows a weak orange spark. What is the most likely cause?

Dirty carburetor bowl
Low engine oil level
Worn ignition coil or incorrect coil-to-flywheel air gap (Correct answer)
Clogged air filter

Correct answer: Worn ignition coil or incorrect coil-to-flywheel air gap

A weak orange spark indicates insufficient coil output, most commonly caused by a deteriorating ignition coil or an incorrect air gap between the coil armature and flywheel magnets.

Question 44: Which type of cooling system uses fins on the cylinder and head to dissipate heat directly into the surrounding air?

Liquid cooling
Air cooling (Correct answer)
Oil cooling
Evaporative cooling

Correct answer: Air cooling

Air-cooled engines use cast fins on the cylinder and head to maximize surface area and radiate heat directly into the airflow around the engine.

Question 45: During the intake stroke in a four-stroke engine, what are the positions of the valves?

Both intake and exhaust valves are open
Both intake and exhaust valves are closed
The intake valve is closed and the exhaust valve is open
The intake valve is open and the exhaust valve is closed (Correct answer)

Correct 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.

Question 46: What is the purpose of the resistor built into many modern spark plugs?

Reduce required ignition coil voltage
Prevent electrode wear
Increase spark energy
Suppress radio frequency interference (RFI) from the ignition system (Correct answer)

Correct answer: Suppress radio frequency interference (RFI) from the ignition system

The resistor inside the spark plug suppresses electromagnetic interference generated by the ignition spark, protecting electronic controls and nearby radio equipment.

Question 47: The process of using the incoming fresh air-fuel charge to push the burnt exhaust gases out of the cylinder is known as:

Porting
Pressurization
Combustion
Scavenging (Correct answer)

Correct answer: Scavenging

Scavenging is the critical process in a two-stroke engine where the fresh mixture entering the cylinder through the transfer ports displaces the exhaust gases from the previous power stroke, pushing them out through the exhaust port.

Question 48: What symptom most clearly indicates the idle mixture screw is set too lean?

Excessive fuel consumption during normal operation
Black smoke emitting from the exhaust at idle
Engine runs rough and tends to stall at idle speed (Correct answer)
Fouled, black-coated spark plug electrode

Correct answer: Engine runs rough and tends to stall at idle speed

A lean idle mixture provides insufficient fuel for stable combustion at low rpm, causing rough running or stalling.

Question 49: A two-stroke engine has a power stroke once _______.

every full revolution (Correct answer)
every half revolution
every three revolutions
every two revolutions

Correct answer: every full revolution

Explanation: In a two-stroke engine, a power stroke occurs once every full revolution of the crankshaft. This contrasts with a four-stroke engine, which has a power stroke once every two revolutions of the crankshaft.

Question 50: On a magneto-based ignition system, what component triggers spark at the correct crankshaft position?

Governor spring
Carburetor float
Battery
Points or electronic trigger module aligned with the flywheel magnets (Correct answer)

Correct answer: Points or electronic trigger module aligned with the flywheel magnets

Breaker points or an electronic trigger module detect the passing of flywheel magnets and signal the coil to collapse its magnetic field and fire the spark plug.

Question 51: A two-stroke engine uses ________ fuel than a four-stroke engine.

less
more (Correct answer)
the same amount of
variable amounts of

Correct answer: more

Explanation: A two-stroke engine typically uses more fuel than a four-stroke engine because it completes a power cycle with every revolution, leading to higher fuel consumption. Additionally, some of the air-fuel mixture in a two-stroke engine can be lost through the exhaust port, further increasing fuel usage.

Question 52: When performing a bench setting for the Height of Cut (HOC) on a reel mower, the measurement should be taken from a flat surface plate to the:

Centerline of the front roller
Top front edge of the bedknife (Correct answer)
Bottom of the rear roller
Lowest point of the reel blades

Correct answer: Top front edge of the bedknife

The Height of Cut is determined by the vertical distance between the bottom of the rollers (representing the ground plane) and the cutting edge of the bedknife. Therefore, when using a gauge on a flat surface, the measurement is taken from the surface plate to the top, front cutting edge of the bedknife.

Question 53: The term 'Frequency of Clip' (FOC) is calculated using which three variables?

Reel diameter, number of blades, and engine RPM
Ground speed, height of cut, and reel speed (RPM)
Reel speed (RPM), number of blades, and ground speed (Correct answer)
Number of blades, bedknife angle, and reel diameter

Correct answer: Reel speed (RPM), number of blades, and ground speed

Frequency of Clip (FOC) is the distance the mower travels forward between each cut. It is a function of how fast the mower is moving (ground speed), how many cutting edges are on the reel (number of blades), and how fast those blades are rotating (reel RPM).

Question 54: During a cooling system pressure test, pressure drops steadily over 10 minutes. What does this indicate?

The thermostat is functioning correctly
A leak in the cooling system (hose, gasket, or component) (Correct answer)
Coolant concentration is too high
Normal thermal contraction of the system

Correct answer: A leak in the cooling system (hose, gasket, or component)

A steady pressure drop during a static pressure test indicates coolant is escaping the system through a leak that must be located and repaired.

Question 55: The primary function of a turbocharger's wastegate on a compact diesel engine is to:

Increase exhaust gas temperature for DPF regeneration.
Cool the compressed intake air before it enters the engine.
Limit the maximum boost pressure to protect the engine. (Correct answer)
Reduce engine noise during high RPM operation.

Correct answer: Limit the maximum boost pressure to protect the engine.

A wastegate is a valve that diverts a portion of the exhaust gas flow around the turbine wheel of the turbocharger. This action limits the turbine's speed, which in turn regulates the speed of the compressor and controls the maximum boost pressure, preventing engine damage from over-boosting.

Question 56: A compact diesel engine is difficult to start, especially in cold weather, and produces excessive white smoke upon starting. Which of the following is the MOST likely cause?

A faulty starter motor
Malfunctioning glow plugs (Correct answer)
Low engine compression
Clogged fuel filter

Correct answer: Malfunctioning glow plugs

Faulty glow plugs are a primary cause of hard starting in cold weather for diesel engines. Glow plugs are heating elements that warm the combustion chamber to aid in ignition. When they fail, the engine struggles to reach the temperature needed for combustion, resulting in hard starting and white smoke (unburnt fuel).

Question 57: What are the two benefits of a two-stroke engine design?

Higher fuel efficiency and lower emissions
Longer lifespan and reduced maintenance requirements
Lightweight and smaller size (Correct answer)
Quieter operation and smoother performance

Correct 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.

Question 58: What is the air gap specification between the ignition coil armature and flywheel magnets used for?

Setting carburetor float height
Controlling fuel metering
Adjusting valve clearance
Setting the magnetic coupling distance for proper coil charging and spark energy (Correct answer)

Correct 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.

Question 59: A technician is troubleshooting a zero-turn mower with a hydrostatic transaxle that is noisy and has a lack of power after a short period of operation. The fluid level is correct. Which of the following is the MOST likely first step in the diagnostic process?

Check the condition of the drive belt and tensioner.
Purge the air from the hydrostatic system. (Correct answer)
Disassemble the hydraulic pump for internal inspection.
Perform a hydraulic pressure test at the pump outlet.

Correct answer: Purge the air from the hydrostatic system.

Noisy operation and a lack of power in a hydrostatic system, especially after a fluid change or service, are classic symptoms of air in the hydraulic fluid (aeration). Purging the system is a non-invasive first step to remove any trapped air, which is critical for proper operation as air compresses and causes inefficient power transfer and noise.

Question 60: An engine overheats only under heavy load but runs normal at idle. Which cooling system component is most likely faulty?

Partially clogged radiator or fins reducing capacity under high heat output (Correct answer)
Carburetor main jet
Fuel cap venting issue
Thermostat stuck open

Correct 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.

Question 61: When diagnosing the cause of a bent crankshaft on a lawnmower, which of the following is the most common cause?

Impact with an immovable object like a rock or tree stump (Correct answer)
Using the wrong viscosity oil
A sheared flywheel key
Over-tightening the spark plug

Correct 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.

Question 62: What causes pre-ignition in a four-stroke engine?

Low engine temperature
A hot spot in the combustion chamber (Correct answer)
Faulty spark plug
Excessive fuel pressure

Correct answer: A hot spot in the combustion chamber

Explanation: Pre-ignition in a four-stroke engine occurs when the air/fuel mixture ignites before the spark plug fires, often due to a hot spot in the combustion chamber. This premature ignition can lead to knocking, engine damage, and reduced performance. Identifying and addressing hot spots is crucial in preventing pre-ignition issues in four-stroke engines.

Question 63: A technician is setting the reel-to-bedknife adjustment. After achieving a clean cut on a single sheet of paper across the full width of the reel, they notice the reel is very difficult to turn by hand and makes a heavy grinding sound. What is the most likely issue?

The bedknife attitude is too aggressive.
The backlapping compound was not fully cleaned off.
The reel-to-bedknife contact is too tight. (Correct answer)
The reel bearings are failing.

Correct answer: The reel-to-bedknife contact is too tight.

The goal is to achieve a clean cut with the lightest possible contact between the reel and bedknife. Excessive contact, even if it cuts paper, creates unnecessary friction, heat, and rapid wear on both the reel and bedknife. The reel should spin relatively freely after adjustment.

Question 64: What ratio of antifreeze to water is typically recommended for year-round protection in most US climates?

25% antifreeze / 75% water
50% antifreeze / 50% water (Correct answer)
75% antifreeze / 25% water
100% antifreeze

Correct answer: 50% antifreeze / 50% water

A 50/50 mixture of antifreeze and water provides freeze protection to approximately -34°F and optimal heat transfer and corrosion protection for most US climates.

Question 65: What physical principle draws fuel from the bowl into the airstream inside a carburetor?

Fuel pump pressure pushing fuel upward
Float buoyancy forcing fuel through the main jet
The venturi effect creating low pressure at the narrowed passage (Correct answer)
Gravity feeding fuel from a raised bowl

Correct answer: The venturi effect creating low pressure at the narrowed passage

Air accelerating through the venturi's restricted passage drops in pressure, creating a vacuum that pulls fuel up from the bowl.

Question 66: How many revolutions of the crankshaft are required to complete one power cycle in a four-stroke engine?

Four revolutions
One revolution
Three revolutions
Two revolutions (Correct answer)

Correct answer: Two revolutions

Explanation: In a four-stroke engine, one power cycle—consisting of intake, compression, power, and exhaust strokes—requires two revolutions of the crankshaft. This means that each piston completes its four-stroke cycle (intake, compression, power, and exhaust) once every two revolutions of the crankshaft.

Question 67: A technician is troubleshooting a generator with a consistently low voltage output of 95V. The engine speed is confirmed to be correct (producing 60 Hz), and swapping the AVR with a known-good unit does not fix the problem. What is the most logical next diagnostic step?

Test the fuel for water contamination.
Replace the main circuit breaker.
Measure the resistance of the rotor windings through the slip rings and brushes. (Correct answer)
Perform an engine compression test.

Correct answer: Measure the resistance of the rotor windings through the slip rings and brushes.

With the engine speed and AVR ruled out, the problem likely lies in the excitation circuit or main windings. The brushes and slip rings are critical components that transfer excitation current from the AVR to the rotor. Worn brushes, dirty slip rings, or high resistance in the rotor windings can weaken the magnetic field, leading to low voltage output. Measuring the resistance across these components is the next logical step.

Question 68: What component in a float-type carburetor controls the fuel level in the bowl?

The needle valve and float assembly (Correct answer)
The throttle plate position
The main jet orifice
The venturi tube diameter

Correct answer: The needle valve and float assembly

The float rises with the fuel level and pushes the needle valve closed to stop fuel flow and maintain the correct bowl height.

Question 69: A technician is servicing a four-stroke engine that runs erratically under changing loads. Which component is most likely responsible for maintaining a consistent engine speed?

Ignition coil
Crankshaft
Flywheel
Governor system (Correct answer)

Correct answer: Governor system

The governor system is designed to automatically adjust the throttle to maintain a steady engine speed regardless of the load being placed on the engine. An erratic speed under changing loads points to a malfunction in this system.

Question 70: Why is it important to use the spark plug type and heat range specified by the engine manufacturer?

Using the wrong heat range can cause fouling, pre-ignition, or engine damage (Correct answer)
Specification only matters for warranty purposes
All spark plugs are interchangeable regardless of specification
Aftermarket plugs are always inferior in quality

Correct 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.

Question 71: Which type of scavenging directs the incoming charge upward in a looping path to force exhaust gases out, with both transfer and exhaust ports located on the same side of the cylinder?

Loop scavenging (Correct answer)
Uniflow scavenging
Cross-flow scavenging
Piston-port scavenging

Correct answer: Loop scavenging

In loop scavenging, the transfer ports are shaped to direct the fresh charge up one side of the cylinder, across the combustion chamber, and down the other side, effectively 'looping' to push out the exhaust gases.

Question 72: A V-twin, air-cooled engine is running rough, overheating, and pushing oily smoke from the crankcase breather tube. A compression test reveals one cylinder has significantly lower compression than the other. What is the MOST likely failure?

A sheared flywheel key
A blown head gasket (Correct answer)
A clogged fuel injector
A failed ignition coil on one cylinder

Correct answer: A blown head gasket

A blown head gasket can create a leak between the combustion chamber and the crankcase (often via the pushrod gallery). This allows hot combustion gases to enter the crankcase, pressurizing it and forcing out oily smoke through the breather. It also directly causes the loss of compression in that cylinder, leading to a rough run condition and overheating. A bad coil would cause a misfire but not pressure in the crankcase. A clogged injector would cause a lean condition. A sheared key affects ignition timing.

Question 73: A lawnmower engine abruptly stopped after the blade struck a large tree root. Now, the engine has a weak or non-existent spark, and the starter rope kicks back violently. What is the MOST likely cause of these symptoms?

The carburetor float is stuck
The impact fouled the spark plug
The flywheel key has sheared (Correct answer)
The low-oil sensor has failed

Correct answer: The flywheel key has sheared

The soft metal flywheel key is designed to shear during a sudden crankshaft stoppage to protect the crankshaft from damage. When it shears, the flywheel spins on the crankshaft, misaligning the flywheel's magnet with the ignition coil. This severely alters the ignition timing, causing a weak/absent spark or a spark at the wrong time, which leads to violent kickback. A fouled plug is possible but less direct. A stuck float affects fuel, not spark.

Question 74: Why do two-stroke engines typically produce more emissions compared to four-stroke engines?

The combustion chamber is larger
They use more fuel per cycle
Two-stroke oil and loss of air-fuel mixture through the exhaust port (Correct answer)
They operate at higher temperatures

Correct answer: Two-stroke oil and loss of air-fuel mixture through the exhaust port

Explanation: Two-stroke engines produce more emissions primarily because they mix oil with the fuel, which burns and produces more pollutants. Additionally, the design of the engine leads to a loss of the air-fuel mixture through the exhaust port, contributing to unburned hydrocarbons and other emissions.

Question 75: What is the purpose of the overflow reservoir connected to a radiator cap on liquid-cooled engines?

Filter coolant before it enters the pump
Capture expanding coolant and return it to the radiator when the system cools (Correct answer)
Store extra fuel
House the thermostat

Correct answer: Capture expanding coolant and return it to the radiator when the system cools

The overflow reservoir captures coolant pushed out by thermal expansion and draws it back in as the system cools, preventing coolant loss and air entry.

Question 76: On a two-stroke engine, the crankshaft turns how many degrees to complete one full cycle:

270 degrees
720 degrees
180 degrees
360 degrees (Correct answer)

Correct answer: 360 degrees

Explanation: In a two-stroke engine, the crankshaft completes one full cycle in 360 degrees of rotation. This means the engine completes all four stages of the combustion process (intake, compression, power, and exhaust) in just one crankshaft revolution, unlike a four-stroke engine which requires 720 degrees.

Question 77: A technician is servicing a commercial-grade V-twin engine and notes it is equipped with an oil filter, an oil pump, and drilled passages in the crankshaft. This combination of components indicates which type of lubrication system?

Pressure-fed lubrication (Correct answer)
Splash lubrication
Two-stroke premix lubrication
Wick-feed lubrication

Correct answer: Pressure-fed lubrication

A full-pressure lubrication system uses an oil pump to draw oil from the sump and force it under pressure through an oil filter and then through drilled passages (galleries) to critical components like crankshaft and connecting rod bearings. The presence of an oil pump and an external, replaceable oil filter are key indicators of this system.

Question 78: A powershift transmission in a piece of utility equipment is exhibiting delayed, rough shifting and a noticeable shudder upon acceleration. Which of the following is the MOST likely cause of these symptoms?

A clogged transmission fluid filter.
A failing clutch pack or contaminated clutch surfaces. (Correct answer)
An incorrectly adjusted shift linkage.
Low hydraulic fluid temperature.

Correct answer: A failing clutch pack or contaminated clutch surfaces.

Shuddering, jerking, and rough or delayed shifting are common symptoms of problems within the clutch packs of a powershift transmission. These issues can be caused by excessive wear on the clutch discs or contamination from leaking seals, which prevents the clutches from engaging smoothly.

Question 79: What is the primary function of the lobes on a camshaft in a four-stroke engine?

To actuate the intake and exhaust valves at the correct time (Correct answer)
To balance the crankshaft's rotation
To create the spark for ignition
To splash lubricate the cylinder walls

Correct answer: To actuate the intake and exhaust valves at the correct time

The egg-shaped lobes on a camshaft are precisely designed to push against valve lifters or rocker arms, converting the camshaft's rotational motion into the linear motion needed to open and close the intake and exhaust valves. The shape and timing of the lobes dictate when the valves open, how long they stay open, and how far they open, which is critical for the engine's performance.

Question 80: A technician performs a voltage drop test on the starter motor's positive cable. With the engine cranking, the multimeter reads 0.8 volts. What does this reading indicate?

The starter motor has excessive internal resistance and should be replaced.
There is high resistance in the positive side of the starter circuit. (Correct answer)
The ground connection between the engine and the battery is faulty.
The battery is fully charged and providing adequate voltage.

Correct answer: There is high resistance in the positive side of the starter circuit.

A voltage drop test measures the amount of voltage 'lost' due to resistance in a circuit. A reading of 0.8 volts on the positive cable during cranking is excessive; a general rule of thumb is that it should not exceed 0.5 volts. This indicates a problem such as a corroded connection, a damaged cable, or a faulty solenoid contact on the positive side of the circuit.

Question 81: What material is most commonly used for small-engine carburetor body construction?

Zinc die-cast alloy (Correct answer)
Stainless steel casting
Stamped steel sheet metal
Machined brass

Correct answer: Zinc die-cast alloy

Zinc die-cast alloy (Zamak) is lightweight, corrosion-resistant to fuel, and easily cast into the complex internal passages a carburetor requires.

Question 82: When testing the AC voltage output from a stator on a small engine, where should the multimeter leads be placed?

One lead on the positive battery terminal and the other lead on the stator output wire.
One lead on the stator output wire and the other lead on the engine block (ground).
One lead on the voltage regulator output and the other lead on the negative battery terminal.
Across the two stator output wires (or pins) coming from under the flywheel housing. (Correct answer)

Correct answer: Across the two stator output wires (or pins) coming from under the flywheel housing.

The stator produces alternating current (AC) voltage. To measure its total output, the multimeter, set to AC volts, must be connected across the two output leads from the stator itself, before the voltage regulator/rectifier. This tests the stator's ability to generate voltage independently of the rest of the charging system.

Question 83: What electrical test can confirm a faulty ignition coil on a small engine without a spark tester?

Measure battery voltage at the coil terminal
Test coil by grounding it to the frame
Check coil for physical cracks only
Measure coil primary and secondary winding resistance with an ohmmeter and compare to specifications (Correct answer)

Correct answer: Measure coil primary and secondary winding resistance with an ohmmeter and compare to specifications

Measuring primary and secondary winding resistance with an ohmmeter and comparing values to the manufacturer's specifications can identify open or shorted coil windings.

Question 84: How does a technician correctly set the ignition coil air gap on a small engine?

Set gap by feel with no measurement needed
Use a dial indicator on the flywheel
Tighten the coil bolts fully without measuring gap
Use a wire feeler gauge between the coil armature legs and flywheel magnets while magnets are aligned (Correct answer)

Correct 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.

Question 85: Upon starting a four-stroke engine for a customer complaint of high oil consumption, a technician observes a consistent stream of blue-tinted smoke from the muffler. This symptom is a classic indicator of which internal engine problem?

The engine is running rich
Coolant is leaking into the cylinder
The fuel is contaminated with water
The engine is burning oil (Correct answer)

Correct answer: The engine is burning oil

Blue or grayish-blue smoke is the result of engine oil entering the combustion chamber and being burned with the fuel/air mixture. This is typically caused by worn piston rings, valve guides, or seals. Black smoke indicates a rich fuel mixture, while heavy white smoke often points to a coolant leak (on liquid-cooled engines) or a blown head gasket.

Question 86: When testing a common rail fuel injector, a technician performs a return flow (back-leak) test. What is the primary purpose of this test?

To identify excessive internal leakage within the injector. (Correct answer)
To check for external fuel leaks around the injector body.
To measure the volume of fuel delivered to the cylinder.
To verify the electrical resistance of the injector solenoid.

Correct answer: To identify excessive internal leakage within the injector.

The return flow, or back-leak, test measures the amount of fuel that bypasses the nozzle and returns to the tank. Excessive return flow indicates internal wear or damage, such as a worn valve seat, which prevents the injector from holding proper pressure for efficient atomization.

Question 87: Which of the following is a primary function of the flywheel in a four-stroke engine?

To store rotational energy (Correct answer)
To open and close the valves
To mix the fuel and air
To provide lubrication to the cylinder

Correct answer: To store rotational energy

The flywheel's main purpose is to store kinetic energy from the power stroke. This stored energy maintains the crankshaft's rotation through the non-power strokes (exhaust, intake, compression), ensuring smooth engine operation.

Question 88: A technician is diagnosing a parasitic draw on a piece of equipment. With the ignition off and all accessories turned off, the multimeter, connected in series with the negative battery cable, reads 250 mA. What is the most appropriate next step?

Begin pulling fuses one by one while observing the multimeter reading. (Correct answer)
Perform a voltage drop test across the main power and ground cables.
Start the engine to check if the charging system can overcome the draw.
Replace the battery, as it is likely failing to hold a charge.

Correct answer: Begin pulling fuses one by one while observing the multimeter reading.

A parasitic draw of 250 mA (0.25 A) is excessive; a normal range is typically under 50 mA. The standard procedure to isolate the source of the draw is to pull fuses one at a time. When the fuse for the problematic circuit is pulled, the amperage reading on the multimeter will drop significantly, identifying which circuit contains the fault.

Question 89: What is the primary purpose of applying an abrasive backlapping compound to a reel and bedknife assembly?

To remove large nicks and damage from the bedknife
To set the initial reel-to-bedknife clearance
To hone and mate the cutting edges of the reel and bedknife (Correct answer)
To establish a relief angle on the reel blades

Correct answer: To hone and mate the cutting edges of the reel and bedknife

Backlapping is a maintenance procedure that uses an abrasive paste to sharpen the reel and bedknife. By spinning the reel in reverse, the compound lightly hones both cutting surfaces, creating a perfectly matched, sharp edge between them. It is used for maintaining a sharp edge between grindings, not for heavy material removal or initial setup.

Question 90: A technician is servicing a portable generator that starts and runs smoothly but produces no AC voltage at the receptacles. The circuit breakers are confirmed to be in the 'ON' position. What is the MOST likely initial diagnostic step?

Measure the engine's RPM to ensure it is at 3600 RPM.
Disassemble the generator end to inspect the stator windings.
Check for residual magnetism and flash the field windings if necessary. (Correct answer)
Replace the Automatic Voltage Regulator (AVR) immediately.

Correct answer: Check for residual magnetism and flash the field windings if necessary.

Generators rely on a small amount of residual magnetism in the rotor to begin generating voltage when started. If this magnetism is lost due to long periods of storage or improper shutdown, the generator cannot 'excite' itself to produce power. Flashing the field with a DC voltage source (like a 12V battery) is a common, non-invasive first step to restore this magnetism before suspecting component failure.

Question 91: What is used to ignite the air/fuel mixture inside the cylinder in a four-stroke engine?

A spark plug (Correct answer)
Fuel injector
Glow plug
Compression stroke

Correct answer: A spark plug

Explanation: In a four-stroke engine, the ignition of the air/fuel mixture inside the cylinder is achieved by a spark plug. The spark plug generates an electric spark that ignites the compressed air/fuel mixture, initiating the combustion process. This controlled ignition leads to the expansion of gases, driving the piston downwards during the power stroke.

Question 92: Which of the following describes the primary function of reed valves in a two-stroke engine?

To mix the oil and fuel automatically before they enter the crankcase.
To act as a one-way check valve for the intake tract, preventing blowback. (Correct answer)
To control the flow of coolant through the engine.
To regulate the timing of the exhaust port opening.

Correct answer: To act as a one-way check valve for the intake tract, preventing blowback.

Reed valves are positioned in the intake tract and open due to the vacuum created in the crankcase as the piston rises. When the piston descends, the pressure in the crankcase forces the flexible reeds to close, preventing the air-fuel mixture from being pushed back out through the carburetor (a phenomenon known as blowback).

Question 93: A two-stroke engine on a string trimmer starts and idles properly, but bogs down and loses all power as soon as the throttle is applied. The carburetor has been cleaned and fuel flow is confirmed to be good. Which of the following components should be inspected next for a potential restriction?

The piston rings
The spark arrestor screen (Correct answer)
The ignition coil
The air filter

Correct answer: The spark arrestor screen

A clogged spark arrestor screen in the muffler is a very common cause of this symptom, especially in two-stroke engines. The carbon buildup prevents exhaust gases from escaping efficiently, creating excessive backpressure that chokes the engine under load. While a dirty air filter can cause low power, it usually presents as a rich running condition (black smoke). A bad coil or rings would likely affect idle as well.

Question 94: What is the correct method for measuring spark plug gap on a small engine?

Gap is factory-set and never needs checking
Flat feeler gauge slid between electrodes
Visual inspection only
Wire-type feeler gauge inserted between center and ground electrode (Correct answer)

Correct answer: Wire-type feeler gauge inserted between center and ground electrode

A wire-type feeler gauge provides an accurate measurement of the spark plug gap because the rounded wire matches the curved electrode shape better than a flat gauge.

Question 95: Which carburetor circuit provides fuel to the engine during idle operation?

Idle circuit (Correct answer)
Choke enrichment circuit
Accelerator pump circuit
Main metering circuit

Correct answer: Idle circuit

The idle circuit meters fuel when the throttle plate is nearly closed and engine speed is low, where the main circuit cannot produce enough vacuum.

Question 96: Which carburetor adjustment directly sets the engine idle speed?

Turning the throttle stop screw in or out (Correct answer)
Replacing the venturi insert with a different size
Rotating the main jet to a larger orifice
Raising or lowering the float height

Correct answer: Turning the throttle stop screw in or out

The throttle stop screw mechanically limits how far the throttle plate closes, setting the minimum airflow and engine idle speed.

Question 97: What is the primary function of the ignition coil in a small engine?

Regulate fuel delivery timing
Step up low battery voltage to high voltage needed to fire the spark plug (Correct answer)
Control valve timing
Filter electrical noise from the charging system

Correct answer: Step up low battery voltage to high voltage needed to fire the spark plug

The ignition coil transforms low primary voltage into the high-voltage spark (typically 20,000–40,000 volts) needed to jump the spark plug gap and ignite the air-fuel mixture.

Question 98: What is the recommended method for cleaning debris from air-cooled engine fins during maintenance?

High-pressure water wash
Wire brush scrubbing
Compressed air blown in the direction of normal airflow (Correct answer)
Solvent soak

Correct answer: Compressed air blown in the direction of normal airflow

Compressed air directed in the normal airflow direction effectively clears debris from fins without damaging the thin metal structures.

Question 99: What does float height measurement determine in a carburetor?

The size of the air bleed passage
The throttle plate angle at idle position
The diameter of the main jet orifice
The fuel level maintained in the float bowl (Correct answer)

Correct answer: The fuel level maintained in the float bowl

Float height determines how high the fuel rises in the bowl before the needle valve closes, directly affecting the fuel level and mixture richness.

Question 100: A technician performs a compression test on a single-cylinder engine and gets a reading of 45 PSI, which is well below the manufacturer's specification. To quickly help determine if the low compression is caused by worn piston rings or a poor valve seal, what is the immediate next diagnostic step?

Check and adjust the valve lash
Perform a cylinder leak-down test
Add a small amount of oil to the cylinder and re-test (Correct answer)
Replace the head gasket

Correct answer: Add a small amount of oil to the cylinder and re-test

This procedure is known as a 'wet' compression test. Adding about a teaspoon of engine oil into the cylinder through the spark plug hole temporarily helps seal the piston rings. If the compression reading increases significantly on the re-test, it indicates the rings are worn. If the reading stays about the same, the leak is likely at the valves or head gasket. This is a faster initial diagnostic step than a leak-down test.

Question 101: A technician is having difficulty pulling the starter rope on a high-compression four-stroke engine. The resistance is extremely high. Which mechanism is designed to make starting easier by slightly opening a valve during the initial part of the compression stroke?

An automatic compression release (ACR) (Correct answer)
A flywheel brake
A rewind spring assist
A governor system

Correct answer: An automatic compression release (ACR)

An automatic compression release (ACR) system, typically mounted on the camshaft, uses a centrifugally activated mechanism. At low cranking speeds, it creates a small bump on the cam lobe that slightly opens the exhaust valve, bleeding off some compression and making the engine easier to turn over. Once the engine starts and RPMs increase, centrifugal force disengages the mechanism.

Question 102: Why is it not advisable to perform a leak-down test on a two-stroke engine?

You can damage the crank seals (Correct answer)
It can cause the engine to flood
It can lead to incorrect compression readings
It may damage the piston rings

Correct answer: You can damage the crank seals

Explanation: Performing a leak-down test on a two-stroke engine can potentially damage the crank seals. These seals are crucial for maintaining proper compression and preventing air or fuel leaks. Applying excessive pressure during the test can cause these seals to fail or become compromised, leading to issues with engine performance and reliability. Therefore, it is not recommended to conduct a leak-down test on a two-stroke engine.

EETC Technician Certification Exam

The EETC Technician Certification Exam evaluates knowledge of small engine technology, covering two-stroke and four-stroke engines, compact diesel, electrical systems, driveline/hydraulics, and mechanical systems. Passing all six areas earns Master Certified Technician status.

100

Questions

120 min

Time Limit

70%

To Pass

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Sources & references

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eetc.org — Fees, exam format, passing score, retake fee, test delivery, eligibility, renewal, test dates, time limit, score validity · verified Oct 2026
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