NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
Question 1
A diesel engine relies on which principle to ignite the air-fuel mixture?
A. Spark ignition
B. Compression ignition
C. Glow plug ignition only
D. Battery ignition
Correct Answer: B
END OF
PAGE
1
, NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
Rationale: Diesel engines ignite fuel through the heat generated by
compressing air. Spark plugs are not used during normal engine
operation.
Question 2
A diesel engine that cranks normally but fails to start after sitting
overnight most likely has:
A. Excessive tire pressure
B. Air entering the fuel system
C. Worn windshield wipers
END OF
PAGE
2
, NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
D. Low coolant level
Correct Answer: B
Rationale: Air leaks in the fuel system can allow fuel to drain back to the
tank, making starting difficult after extended periods.
Question 3
The primary purpose of the fuel-water separator is to:
A. Increase fuel pressure
B. Remove water from diesel fuel
END OF
PAGE
3
, NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
C. Cool the injectors
D. Lubricate the injection pump
Correct Answer: B
Rationale: Water contamination can damage fuel injection components
and reduce engine performance.
Question 4
Black exhaust smoke from a diesel engine usually indicates:
A. Excessive fuel or insufficient air
END OF
PAGE
4
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
Question 1
A diesel engine relies on which principle to ignite the air-fuel mixture?
A. Spark ignition
B. Compression ignition
C. Glow plug ignition only
D. Battery ignition
Correct Answer: B
END OF
PAGE
1
, NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
Rationale: Diesel engines ignite fuel through the heat generated by
compressing air. Spark plugs are not used during normal engine
operation.
Question 2
A diesel engine that cranks normally but fails to start after sitting
overnight most likely has:
A. Excessive tire pressure
B. Air entering the fuel system
C. Worn windshield wipers
END OF
PAGE
2
, NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
D. Low coolant level
Correct Answer: B
Rationale: Air leaks in the fuel system can allow fuel to drain back to the
tank, making starting difficult after extended periods.
Question 3
The primary purpose of the fuel-water separator is to:
A. Increase fuel pressure
B. Remove water from diesel fuel
END OF
PAGE
3
, NYC AUTO MECHANIC LATEST
(DIESEL) (DCAS)
CERTIFICATION
PRACTICE EXAM
QUESTIONS AND
ANSWERS 2026 - 2027
C. Cool the injectors
D. Lubricate the injection pump
Correct Answer: B
Rationale: Water contamination can damage fuel injection components
and reduce engine performance.
Question 4
Black exhaust smoke from a diesel engine usually indicates:
A. Excessive fuel or insufficient air
END OF
PAGE
4
