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100+ Free Automotive Servicing NC I Practice Questions
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2026 Statistics
Key Facts: Automotive Servicing NC I Exam
Competent
Passing Grade
TESDA
1 day
Typical Duration
Assessment centers
₱660.00
Standard Fee
Official TESDA rate
288-469h
Training Duration
Standard program length
5 years
Certificate Validity
TESDA NC I
Any time
Retake Wait Time
For reassessment
The TESDA Automotive Servicing NC I assessment in the Philippines is a competency-based exam consisting of a hands-on practical demonstration, oral questioning, and a written test. It covers gas and diesel engine tune-ups, electrical unit replacement, and underchassis systems. The standard assessment fee is ₱660.00.
Sample Automotive Servicing NC I Practice Questions
Try these sample questions to test your Automotive Servicing NC I exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 100+ question experience with AI tutoring.
1A technician is checking the resistance of a diesel glow plug using a digital multimeter. What is the typical resistance value of a good glow plug at room temperature?
A.Less than 2 ohms (typically 0.5 to 1.5 ohms)
B.Between 10 and 20 ohms
C.Between 50 and 100 ohms
D.Infinite resistance (open circuit)
Explanation: A good diesel engine glow plug has a very low resistance when cold, typically ranging from 0.5 to 1.5 ohms. This low resistance allows high current to flow through the heating element, heating it up rapidly to assist in diesel combustion during cold starts. High resistance or infinite resistance indicates a failing or open glow plug that must be replaced.
2After replacing the fuel filters on a conventional diesel engine, the engine cranks but refuses to start. What is the most appropriate next step?
A.Bleed the air from the diesel fuel system starting from the lowest pressure point to the highest pressure point.
B.Keep cranking the engine continuously until it starts to build fuel pressure.
C.Spray starting fluid directly into the air intake to force the engine to start.
D.Loosen the fuel tank cap to relieve any vacuum build-up in the tank.
Explanation: Diesel fuel systems must be completely free of air to function correctly because air is compressible, preventing fuel pressure from opening the injectors. After replacing fuel filters, air becomes trapped and must be bled out starting at the primary filter, then the injection pump gallery, and finally at the injectors if necessary. Continuous cranking can damage the starter motor and battery, while starting fluid can cause pre-ignition and engine damage.
3When installing a spin-on type diesel fuel filter, which procedure should the technician follow to prevent air lock and dry running of the transfer pump?
A.Fill the new filter with clean diesel fuel before installing it and lubricate the gasket with clean engine oil or diesel.
B.Install the filter dry, then crank the engine for 30 seconds to prime the system.
C.Coat the filter threads with thread locker and tighten it with a filter wrench as hard as possible.
D.Leave the filter half-full of water to allow the water separator to function immediately.
Explanation: Filling the new diesel fuel filter with clean diesel fuel before installation minimizes the amount of air introduced into the fuel lines, preventing hard-starting and air-lock conditions. Lubricating the rubber gasket with clean oil or diesel ensures a proper seal and allows for easy removal in the future. Installing the filter dry leads to extensive air entrapment and dry running of the transfer pump.
4What is the primary difference in combustion chamber design between a direct injection (DI) diesel engine and an indirect injection (IDI) diesel engine?
A.In DI engines, fuel is injected directly into a combustion chamber formed in the piston crown, whereas IDI engines inject fuel into a small pre-chamber.
B.DI engines use spark plugs for combustion, whereas IDI engines rely purely on heat of compression.
C.DI engines inject fuel into the intake manifold, whereas IDI engines inject fuel directly into the cylinder.
D.DI engines have the fuel injectors mounted in the crankcase, whereas IDI engines mount them in the cylinder head.
Explanation: Direct Injection (DI) engines inject fuel directly into the main combustion chamber, which is typically shaped into the top of the piston crown. Indirect Injection (IDI) engines inject fuel into a separate, smaller chamber (pre-combustion chamber or swirl chamber) located in the cylinder head, where combustion starts before spreading to the main cylinder. Spark plugs are not used in either diesel design, and injectors are never mounted in the crankcase.
5A diesel passenger vehicle emits heavy black smoke from the exhaust during acceleration. What is the most likely cause of this symptom?
A.An excessive amount of fuel relative to available air (rich mixture) due to a restricted air intake or faulty injectors.
B.Coolant leaking into the combustion chamber due to a blown cylinder head gasket.
C.Engine oil leaking past the valve stem seals or piston rings into the combustion chamber.
D.The fuel tank containing a high concentration of gasoline instead of diesel fuel.
Explanation: Black smoke from a diesel engine indicates incomplete combustion of fuel, which occurs when there is an over-rich mixture (excessive fuel or insufficient air). Common causes include a dirty or restricted air filter, a faulty turbocharger, or failing fuel injectors that deliver too much fuel. Coolant leaks produce white smoke, while engine oil burning produces blue or gray smoke.
6When performing a compression test on a diesel engine, why must a specialized high-pressure diesel compression gauge be used instead of a standard gasoline compression gauge?
A.Diesel engines have much higher compression pressures (typically 300 to 500 psi) which would exceed the limit and damage a gasoline gauge.
B.Diesel engines require the gauge to be filled with diesel fuel during testing.
C.Gasoline compression gauges only read vacuum and cannot measure positive pressure.
D.Diesel compression gauges are electronic and connect to the vehicle's OBD-II port.
Explanation: Diesel engines operate on much higher compression ratios than gasoline engines to generate the heat needed for self-ignition. As a result, diesel compression pressures reach 300 to 500 psi (or higher), whereas gasoline engines typically generate 125 to 180 psi. Using a gasoline engine gauge on a diesel engine would peg the needle, blow the internal seals, or rupture the gauge, posing a safety hazard.
7What is the primary function of the fuel injection pump in a conventional distributor-type (VE) diesel fuel system?
A.To pressurize fuel to the required injection pressure and distribute it to each cylinder in the correct firing order.
B.To mix fuel and air in the correct ratio before delivering it to the intake manifold.
C.To filter out water and fine dirt particles from the fuel tank before it reaches the lift pump.
D.To cool down the fuel before returning it to the main fuel tank.
Explanation: In conventional diesel systems, the fuel injection pump is the heart of the engine. It pressurizes the diesel fuel to the high levels required to open the mechanical injectors and timed distribution to each cylinder according to the engine's firing order. Mixing air and fuel occurs inside the cylinder itself, and filtering is handled by the fuel filters.
8A technician notices the 'water-in-fuel' warning light illuminated on the instrument cluster of a diesel vehicle. What service procedure must be performed immediately?
A.Open the drain valve at the bottom of the fuel filter/water separator to drain the accumulated water until clean diesel flows.
B.Add alcohol to the fuel tank to absorb the water and burn it through the engine.
C.Replace the high-pressure common rail fuel pump because it has failed.
D.Drain and discard the entire contents of the fuel tank at an approved disposal site.
Explanation: The fuel filter/water separator collects water because water is denser than diesel fuel and settles to the bottom of the housing. When the sensor detects accumulated water, the warning light turns on. The technician must open the petcock or drain plug at the bottom of the filter to drain the water until clean fuel appears. Draining the entire tank or replacing the pump is unnecessary unless severe contamination or pump damage has occurred.
9On a modern Common Rail Direct Injection (CRDI) diesel engine, what is the role of the rail pressure sensor?
A.It monitors actual fuel pressure in the common rail and sends a signal to the ECU to regulate pressure via the control valve.
B.It measures the boost pressure of the intake air from the turbocharger.
C.It detects the presence of air bubbles in the low-pressure fuel return line.
D.It measures the temperature of the exhaust gas before it enters the catalytic converter.
Explanation: The rail pressure sensor monitors the high pressure of the fuel inside the common rail (which can exceed 20,000 psi). It provides continuous voltage feedback to the Engine Control Unit (ECU), which adjusts the fuel metering valve or pressure regulator to maintain the optimum pressure for current engine operating conditions. Boost pressure is measured by the MAP sensor, not the rail pressure sensor.
10When testing a mechanical diesel injector using a manual nozzle tester, what three characteristics should the technician look for?
A.Opening pressure (pop pressure), spray pattern atomization, and seat leakage (dripping).
B.Electrical resistance, solenoid response time, and voltage drop.
C.Fuel return temperature, fuel flow rate in liters per minute, and housing vibration.
D.O-ring sealing compression, nozzle tip color, and nozzle tip diameter.
Explanation: A manual diesel injector tester (pop tester) is used to verify mechanical injectors. The technician checks: 1) the opening (pop) pressure to ensure it matches specifications; 2) the spray pattern to verify fine, uniform atomization without solid streams; and 3) seat tightness to make sure the injector nozzle does not drip or leak fuel before reaching opening pressure. Solenoid checks only apply to electronic injectors.
About the Automotive Servicing NC I Practice Questions
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