cylinder tester Interview Questions and Answers

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Cylinder Tester Interview Questions and Answers

  1. What is a cylinder tester and how does it work?

    • Answer: A cylinder tester is a diagnostic tool used to assess the condition of internal combustion engine cylinders. It measures compression pressure, indicating the health of piston rings, valves, and head gasket. It works by screwing into the spark plug hole, then cranking the engine to measure the pressure built up within the cylinder. Low pressure indicates leaks or malfunctions.

  2. Describe the different types of cylinder testers.

    • Answer: There are analog and digital cylinder testers. Analog testers use a gauge with a needle to display pressure, while digital testers offer a more precise reading with a digital display, often including features like data logging and peak pressure hold.

  3. What are the safety precautions when using a cylinder tester?

    • Answer: Always wear safety glasses. Ensure the engine is off and cool. Never use the tester on a running engine. Use appropriate adapters to fit different spark plug sizes. Be aware of moving parts during engine cranking.

  4. How do you interpret the readings from a cylinder tester?

    • Answer: Consistent readings across all cylinders indicate good health. Significant variations suggest problems in a specific cylinder, possibly due to worn piston rings, leaking valves, or a blown head gasket. Consult the vehicle's specifications for acceptable pressure ranges.

  5. What are the common causes of low compression in a cylinder?

    • Answer: Worn or broken piston rings, burned or leaking valves, a blown head gasket, cracked cylinder head or block, and excessive valve clearance are common culprits.

  6. How does the compression ratio affect cylinder pressure readings?

    • Answer: A higher compression ratio results in higher cylinder pressure readings under ideal conditions. Lower compression ratios result in lower pressure readings.

  7. What is the significance of a wet and dry compression test?

    • Answer: A wet compression test involves adding a small amount of oil into the cylinder before the test. If the pressure increases significantly, it suggests worn piston rings are the likely cause of low compression. If not, the issue may lie with the valves or head gasket.

  8. What tools are needed besides the cylinder tester for a complete compression test?

    • Answer: You'll need spark plug sockets, a wrench to remove the spark plugs, an assistant to crank the engine, engine oil (for a wet compression test), and a shop rag to clean up any oil spills.

  9. How do you ensure accurate readings from a cylinder tester?

    • Answer: Fully charge the battery, ensure the engine is at operating temperature, use the correct adapter, crank the engine consistently for the appropriate number of revolutions, and repeat the test several times per cylinder for average readings.

  10. What are some limitations of a cylinder compression test?

    • Answer: A compression test doesn't pinpoint the exact cause of low compression; it only indicates that a problem exists. Minor leaks might be missed, and other factors like ignition timing or fuel delivery aren't evaluated.

  11. How often should a cylinder compression test be performed?

    • Answer: It depends on the vehicle and its usage. Regular maintenance schedules may recommend it, or it might be performed when symptoms like rough running or loss of power are noticed.

  12. What are the typical pressure readings for a healthy cylinder in a gasoline engine?

    • Answer: This varies widely by engine design and size but generally ranges from 120 to 180 PSI (pounds per square inch). Consult the vehicle's repair manual for specifications.

  13. Explain the procedure for performing a wet compression test.

    • Answer: After the dry compression test, add a small amount (typically one tablespoon) of engine oil into the cylinder through the spark plug hole. Re-install the spark plug, then repeat the compression test. Compare the before and after readings.

  14. How do you troubleshoot a cylinder tester that's not working correctly?

    • Answer: Check the gauge for accuracy, verify the connections and adapters are secure and fitting properly, ensure the battery is adequately charged for sufficient cranking speed. Inspect the tester for any damage.

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