8.1 Answer the following questions with reference to an exhaust gas analysis - NSC Mechanical Technology Automotive - Question 8 - 2021 - Paper 1
Question 8
8.1 Answer the following questions with reference to an exhaust gas analysis.
8.1.1 State TWO causes of a low CO₂ exhaust gas reading.
8.1.2 State TWO corrective m... show full transcript
Worked Solution & Example Answer:8.1 Answer the following questions with reference to an exhaust gas analysis - NSC Mechanical Technology Automotive - Question 8 - 2021 - Paper 1
Step 1
State TWO causes of a low CO₂ exhaust gas reading.
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Answer
Too rich air/fuel mixture due to excessive fuel delivery or improper operation of the fuel system.
Ignition misfire or a blown cylinder head/block.
Step 2
State TWO corrective measures for the causes stated in QUESTION 8.1.1.
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Answer
Reset the fuel mixture to achieve the correct air/fuel ratio.
Replace the air filter to ensure proper airflow.
Step 3
State TWO exhaust gas readings, as detected by a gas analyser, which are caused by a lean air/fuel mixture.
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High oxygen (O₂) levels indicate incomplete combustion.
High carbon dioxide (CO₂) levels as a result of low combustion efficiency.
Step 4
State ONE cause and ONE corrective measure for the following cylinder leakage test results: Hissing sound at the exhaust pipe.
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Answer
Cause: Leaking exhaust valve.
Corrective Measure: Replace the exhaust valve to ensure proper sealing.
Step 5
State ONE cause and ONE corrective measure for the following cylinder leakage test results: Bubbles in the radiator water.
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Answer
Cause: Blown head gasket.
Corrective Measure: Replace the head gasket to restore the engine's integrity.
Step 6
Explain why an internal combustion engine should be at normal operating temperature when diagnostic tests are performed.
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Answer
An internal combustion engine must be at normal operating temperature to allow for proper expansion of components and accurate diagnostic readings. Cold components may lead to misleading results, as certain diagnostic conditions may only arise at the engine’s optimal temperature.
Step 7
Complete the table below by writing down the question numbers (8.5.1 to 8.5.4) and the answer.
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8.5.1: Replace fuel filter.
8.5.2: Clean the strainer of any obstructions.
8.5.3: Check and correct the voltage to the pump.
8.5.4: Replace the pump if it is found to be non-operational.
Step 8
State THREE manufacturer’s specifications required before an oil pressure test can be done.
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Ensure the oil temperature is at the manufacturer's specified operating range.
Confirm the oil pressure is assessed while the engine is at idle.
Ensure oil pressure readings are taken when the engine is at various RPM levels, as per manufacturer guidelines.
Step 9
Explain FOUR steps to perform a radiator cap pressure test.
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Obtain the radiator cap’s opening pressure specifications, usually stamped on the cap.
Install the cap onto the adapter of the cooling system pressure tester.
Pump up the tester while watching the pressure gauge to determine if the pressure achieves the specified opening level.
Note the reading when the pressure is released to check for leakage or malfunction.
