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5.1 Describe how a wet compression test is done on an internal combustion engine - NSC Mechanical Technology Automotive - Question 5 - 2022 - Paper 1
Question 5
5.1 Describe how a wet compression test is done on an internal combustion engine. 5.2 Explain the functions of the following tests done on an internal combustion en... show full transcript
Worked Solution & Example Answer:5.1 Describe how a wet compression test is done on an internal combustion engine - NSC Mechanical Technology Automotive - Question 5 - 2022 - Paper 1
Step 1
Describe how a wet compression test is done on an internal combustion engine.
Answer
In a wet compression test, first, some oil is poured or squirted into the piston through the spark plug hole. This oil helps to seal any gaps that may exist in the rings or cylinder walls. The compression tester is then attached to the spark plug hole, and the engine is cranked to perform the compression test. The readings from this test are compared to the dry compression test readings to determine the condition of the engine.
Step 2
Explain the functions of the following tests done on an internal combustion engine: Compression test.
Answer
The compression test indicates the amount of compression pressure created by the piston in the cylinder. This pressure measurement helps to assess the engine's health, revealing issues such as worn piston rings, valve problems, or blown head gaskets.
Step 3
Explain the functions of the following tests done on an internal combustion engine: Cylinder leakage test.
Answer
The cylinder leakage test measures the amount of compressed air leaking from the cylinder. It also helps identify the location of any leakage, whether it’s through the valves, piston rings, or cylinder walls. This information is crucial in diagnosing the integrity of the engine's cylinders.
Step 4
State FOUR precautions to be taken when using a gas analyser.
Answer
- Ensure the inlet hose is not stepped on and remains free of obstructions.
- Check that the hose connection is airtight, and the valve is closed.
- Make sure there are no exhaust leaks present.
- Regularly blow out any condensate from the hose and pick-up probe, and drain the condenser after each use.
Step 5
Explain how the optical alignment gauges are used to measure wheel alignment after they have been calibrated.
Answer
To measure wheel alignment using optical alignment gauges, follow these steps: First, center the steering on the vehicle. Then, position the tracking gauge against the front wheels. Use a periscope to identify the alignment mark and adjust if necessary. Look through the periscope and align the vertical line with the triangle by making necessary adjustments. Finally, record the toe-in and toe-out values.
Step 6
Describe how you would conduct a computerised diagnostic test on a vehicle using the on-board diagnostics (OBD-II) scanner.
Answer
To conduct a computerised diagnostic test using an OBD-II scanner, first plug the diagnostic tool into the OBD-II port of the vehicle. Next, ensure the vehicle's ignition is turned on. Then, start the diagnostic scan with the scanner while it retrieves trouble codes from the vehicle. Finally, analyze these codes to assist in diagnosing the vehicle's issue.
Step 7