Postal Exam 943/944/945
Study Guide USPS EXAM
1. When diagnosing a battery that repeatedly goes dead overnight, the most
important first test is:
A. Radiator pressure test
B. Parasitic draw test
C. Compression test
D. Fuel pressure test
Answer: B
Rationale: An overnight battery drain is usually caused by an excessive
parasitic electrical draw.
2. A fully charged 12-volt battery should read approximately:
A. 10.5 volts
B. 11.2 volts
C. 12.6 volts
D. 14.8 volts
Answer: C
Rationale: A healthy fully charged battery is typically around 12.6 volts.
3. The primary purpose of the alternator is to:
A. Store electrical energy
B. Start the engine
C. Recharge the battery and supply electrical power
D. Reduce engine compression
Answer: C
Rationale: The alternator provides current after the engine starts and
maintains battery charge.
4. A slipping serpentine belt can cause:
A. Lower alternator output
B. Higher oil pressure
C. More compression
, D. Better fuel atomization
Answer: A
Rationale: Belt slip reduces alternator drive and charging performance.
5. The device that prevents engine overheating by regulating coolant flow is
the:
A. Thermostat
B. Fuel injector
C. Catalytic converter
D. PCV valve
Answer: A
Rationale: The thermostat controls coolant flow to maintain engine
temperature.
6. If engine oil appears milky, the most likely cause is:
A. Overfilled transmission fluid
B. Coolant contamination
C. Low tire pressure
D. Broken alternator belt
Answer: B
Rationale: Milky oil commonly indicates coolant entering the oil system.
7. A cylinder leakage test is used to detect:
A. Tire wear
B. Internal engine sealing problems
C. Brake fade
D. Alternator ripple
Answer: B
Rationale: It helps locate leaks past valves, rings, or head gaskets.
8. Air escaping through the radiator during a leak-down test most likely points
to:
A. Worn spark plugs
B. Defective head gasket
C. Low washer fluid
D. Faulty starter motor
Answer: B
Rationale: Bubbles in the radiator suggest combustion gases entering the
cooling system.
Study Guide USPS EXAM
1. When diagnosing a battery that repeatedly goes dead overnight, the most
important first test is:
A. Radiator pressure test
B. Parasitic draw test
C. Compression test
D. Fuel pressure test
Answer: B
Rationale: An overnight battery drain is usually caused by an excessive
parasitic electrical draw.
2. A fully charged 12-volt battery should read approximately:
A. 10.5 volts
B. 11.2 volts
C. 12.6 volts
D. 14.8 volts
Answer: C
Rationale: A healthy fully charged battery is typically around 12.6 volts.
3. The primary purpose of the alternator is to:
A. Store electrical energy
B. Start the engine
C. Recharge the battery and supply electrical power
D. Reduce engine compression
Answer: C
Rationale: The alternator provides current after the engine starts and
maintains battery charge.
4. A slipping serpentine belt can cause:
A. Lower alternator output
B. Higher oil pressure
C. More compression
, D. Better fuel atomization
Answer: A
Rationale: Belt slip reduces alternator drive and charging performance.
5. The device that prevents engine overheating by regulating coolant flow is
the:
A. Thermostat
B. Fuel injector
C. Catalytic converter
D. PCV valve
Answer: A
Rationale: The thermostat controls coolant flow to maintain engine
temperature.
6. If engine oil appears milky, the most likely cause is:
A. Overfilled transmission fluid
B. Coolant contamination
C. Low tire pressure
D. Broken alternator belt
Answer: B
Rationale: Milky oil commonly indicates coolant entering the oil system.
7. A cylinder leakage test is used to detect:
A. Tire wear
B. Internal engine sealing problems
C. Brake fade
D. Alternator ripple
Answer: B
Rationale: It helps locate leaks past valves, rings, or head gaskets.
8. Air escaping through the radiator during a leak-down test most likely points
to:
A. Worn spark plugs
B. Defective head gasket
C. Low washer fluid
D. Faulty starter motor
Answer: B
Rationale: Bubbles in the radiator suggest combustion gases entering the
cooling system.
