3.1 Name TWO devices that are used to test the hardness of a metal - NSC Mechanical Technology Automotive - Question 3 - 2017 - Paper 1

Using a compression tester on an engine is crucial for several reasons:

1. Check for worn cylinders: This helps in diagnosing the condition of the cylinder walls, ensuring optimal engine performance.
2. Identify issues with piston rings: A compression tester can reveal if the piston rings are worn, which could lead to loss of compression.
3. Detect leakage in the engine: By measuring compression, one can identify problems such as leaks in valves or head gaskets that affect engine efficiency.

A tensile tester measures the resistance of a material to a static or slowly applied tensile axial force. The primary function is to determine how much force a material can withstand before failing, providing valuable information about its mechanical properties.

Two reasons for a high carbon monoxide (CO) reading in exhaust gases are:

1. Rich mixture setting: This occurs when there's too much fuel relative to air in the combustion process, leading to incomplete combustion and higher CO emissions.
2. Incorrect idle speed: If the engine idle speed is set too low, it can cause inefficient combustion, resulting in elevated CO levels in the exhaust.

When using a multi meter, it is essential to adhere to the following operating rules:

1. Ensure correct socket connections: Always check that the measuring leads are inserted into the correct sockets for the intended measurement.
2. Select the appropriate function: Turn the multi meter's function switch to the desired measurement type before taking readings.
3. Start with the highest range: If uncertain about the expected measurement, begin with the highest range setting and adjust downward as needed for accurate results.