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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
Question 8
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.
Answer
- High oxygen (O₂) levels: This indicates incomplete combustion due to a lean fuel mixture.
- Low carbon dioxide (CO₂) levels: A lean mixture can lead to insufficient combustion products.
- High nitrogen oxide (NOₓ) levels: Excess air in the combustion process produces more NOₓ.
Step 2
State THREE possible causes of high levels of hydrocarbon (HC) readings in the exhaust gas of an internal combustion engine.
Answer
- Incomplete combustion: This can occur if there is insufficient fuel or improper air-fuel mixture.
- Improper valve timing: Incorrect timing can prevent the efficient intake and exhaust of gases, resulting in HC emissions.
- Faulty ignition system: Issues with spark plugs or ignition timing can lead to misfires and increased HC levels.
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.
Answer
| Causes | Corrective Measures |
|---|---|
| Blown cylinder head gasket | Replace with new gasket |
| Cracked cylinder head | Replace or 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.
Answer
- Oil pressure at idling speed: If the oil pressure is too low, it can cause bubbles in the coolant.
- Oil pressure after few revolutions: Oil pressure fluctuations can introduce air into the cooling system.
Step 5
Name THREE manufacturer's specifications that must be obtained before conducting an oil pressure test.
Answer
- Oil pressure at idling speed: Must be within manufacturer’s specifications.
- Oil pressure at high revolutions: Must be checked according to specs to ensure engine integrity.
- Oil pressure when engine is cold: This is crucial to ensure proper lubrication and prevention of damage.
Step 6
State FOUR precautions that must be adhered to while setting up the fuel pressure tester.
Answer
- Wear the correct PPE, such as gloves and goggles, to ensure safety.
- Ensure the tester can read the fuel pressure accurately.
- Keep the area clean before removing the sender unit to prevent contamination.
- Place the tester away from flammable materials while the engine is running.
Step 7