8.1 TABLE 8.1 below shows the results of the gas analysis of an internal combustion engine - NSC Mechanical Technology Automotive - Question 8 - 2023 - Paper 1
Question 8
8.1 TABLE 8.1 below shows the results of the gas analysis of an internal combustion engine. Complete TABLE 8.1 by giving ONE cause and ONE appropriate corrective mea... show full transcript
Worked Solution & Example Answer:8.1 TABLE 8.1 below shows the results of the gas analysis of an internal combustion engine - NSC Mechanical Technology Automotive - Question 8 - 2023 - Paper 1
Step 1
8.1 High oxygen (O2) reading
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Answer
One cause for a high oxygen (O2) reading could be a too lean air-fuel ratio. To correct this issue, the fuel mixture should be reset.
Step 2
8.1 High hydrocarbon (HC) reading
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A possible cause for a high hydrocarbon (HC) reading is excessive unburned fuel. The appropriate corrective measure would be to reset the fuel mixture.
Step 3
8.2.1 Explain why the high-tension lead is removed.
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This step is conducted to prevent the distribution of high voltage and to avoid electrical shock while performing the test.
Step 4
8.2.2 Explain why the fuel-injection system is unplugged.
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Unplugging the fuel-injection system prevents fuel from entering the exhaust system, which is crucial for accurate compression readings.
Step 5
8.2.3 Explain the reason for fully opening the throttle valve.
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Opening the throttle valve allows air to enter the cylinder freely, ensuring an accurate measurement of the cylinder compression.
Step 6
8.2.4 Explain why the readings are recorded.
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Recording the readings helps to compare them against the specifications and to check if the pressure is correct or not.
Step 7
8.3.1 Hissing sound at the air intake
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A likely cause is leaking inlet valves. This can be rectified by replacing or reseating the valves.
Step 8
8.3.2 Hissing sound at the dipstick
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This sound indicates worn piston rings. The appropriate corrective measure would be to overhaul the engine and fit new piston rings.
Step 9
8.4 State THREE causes of a high oil-pressure reading.
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Three possible causes of a high oil-pressure reading may include:
Blocked oil passages.
Too little crankshaft bearing clearance.
Oil viscosity being too high.
Step 10
8.5.1 State TWO manufacturer’s specifications before conducting the fuel pressure test.
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Fuel pressure should be verified when the engine is idling.
Fuel pressure must also be checked on high revolutions.
Step 11
8.5.2 Where is the fuel-pressure tester inserted?
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The fuel-pressure tester is inserted at the fuel line.
Step 12
8.5.3 Explain why the rubber pipe may not be worn.
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If the rubber pipe is worn, it could lead to fuel leaks, which would provide inaccurate results and pose a fire hazard.
Step 13
8.6 State FOUR causes of pressure drop during a cooling system pressure test.
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Four possible causes for pressure drop may include:
Coolant leaks from between gaskets/seals of the cooling system.
