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8.1 State THREE exhaust gas analyser readings that indicate a lean fuel mixture - NSC Mechanical Technology Automotive - Question 8 - 2022 - Paper 1

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8.1 State THREE exhaust gas analyser readings that indicate a lean fuel mixture. 8.2 State THREE possible causes of high levels of hydrocarbon (HC) readings in the ... show full transcript

Worked Solution & Example Answer:8.1 State THREE exhaust gas analyser readings that indicate a lean fuel mixture - NSC Mechanical Technology Automotive - Question 8 - 2022 - Paper 1

Step 1

State THREE exhaust gas analyser readings that indicate a lean fuel mixture.

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Answer

  1. High Oxygen (O2) levels.
  2. Low Carbon Dioxide (CO2) levels.
  3. High Nitrogen Oxide (NOx) levels.

Step 2

State THREE possible causes of high levels of hydrocarbon (HC) readings in the exhaust gas of an internal combustion engine.

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Answer

  1. Incomplete combustion.
  2. Improper valve timing.
  3. Faulty air management system.

Step 3

Tabulate TWO possible causes and their corrective measures when two adjacent cylinders have very low but similar readings when doing a compression test on a four-stroke internal combustion engine.

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Answer

CausesCorrective Measures
Blown cylinder head gasketReplace with new gasket
Cracked cylinder headReplace/repair cylinder head

Step 4

State TWO causes of bubbles in the radiator water when a cylinder leakage test is conducted on an internal combustion engine.

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Answer

  1. Oil pressure at idling speed.
  2. Oil pressure at high revolutions.

Step 5

Name THREE manufacturer's specifications that must be obtained before conducting an oil pressure test.

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Answer

  1. Oil pressure when engine is cold.
  2. Oil pressure when engine is hot.
  3. Oil pressure when engine is not running.

Step 6

State FOUR precautions that must be adhered to while setting up the fuel pressure tester.

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Answer

  1. Ensure correct PPE is worn.
  2. Clean the area around the sender unit before removal.
  3. Ensure the tester is in good working condition.
  4. Position the tester at a safe distance from the running engine.

Step 7

The pressure dropped during a radiator pressure test. State FOUR measures to correct the pressure drop.

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114 rated

Answer

  1. Repair leaks between components / gasket leaks.
  2. Repair leaking hoses.
  3. Repair or replace leaking water pump.
  4. Repair or replace leaking radiator.

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