8.1 Which gases are analysed with a gas analyser? 8.2 State THREE manufacturer's specifications that must be obtained for a specific engine when conducting a gas analysing test - NSC Mechanical Technology Automotive - Question 8 - 2018 - Paper 1

Three key manufacturer's specifications needed for conducting a gas analysing test are:

1. Percentage of Hydrocarbon (HC)
2. Maximum permissible levels of Carbon monoxide (CO)
3. Levels of Nitrogen oxides (NOₓ)

Two possible results from a cylinder leakage test include:

1. Hissing noise at the intake manifold, indicating a potential leak.
2. Hissing noise at the exhaust pipe, which suggests leakage in the exhaust system.

Two common causes of cylinder leakages are:

1. Worn cylinder walls
2. Leaking exhaust valves

The procedures for conducting a compression test are as follows:

1. Start the engine and warm it up to normal operating temperature.
2. Disconnect the fuel supply and ignition system to prevent accidental starts.
3. Remove spark plugs to allow for easier access.
4. Connect the compression tester securely to the first cylinder.
5. Depress the throttle fully and crank the engine for a few revolutions.
6. Record the pressure reading and compare it against manufacturer specifications for each cylinder.

Two important reasons for low oil pressure might include:

1. A worn oil pump which may be unable to maintain adequate pressure.
2. Blocked oil pump screen or filter, restricting oil flow.

To conduct a cooling system pressure test, follow these steps:

1. Start the engine and allow it to warm up. Make sure the radiator pressure tester is fitted to the radiator.
2. Pressurize the cooling system according to the manufacturer’s specifications.
3. Monitor the pressure reading; if it drops, there may be leaks.
4. Make a visual check for leaks around hoses and fittings.
5. Inspect the radiator cap and its seal for cracks and damage.
6. Check the vacuum valve for proper function.