Final answer:
During a compression check, a weak cylinder must be inspected for issues with valves, piston rings, cylinder wall, and the cylinder head gasket. It's crucial to ensure there are no gas leaks and that the cylinder maintains its integrity.
Step-by-step explanation:
When a compression check reveals a weak cylinder, it is essential to inspect several components. First, check the cylinder's valves for proper sealing. If the valves are not the issue, proceed to inspect the piston rings and the cylinder wall for wear or damage. Additionally, the cylinder head gasket should be examined for signs of failure. It's important to ensure that the gas is not leaking out, the cylinder integrity is maintained, and that it does not change size, especially given that it won't change significantly as it warms, according to the reference provided.
In context with the references cited, a scenario where the cylinder contains 500 g of helium at 120 atm and 20 °C and the valve is leaky could relate to an understanding of the importance of cylinder integrity in maintaining pressure, though the specifics of this situation pertain to a gas escape rather than a compression check in an engine or similar system. Nonetheless, ensuring a leak-proof system is crucial in both cases.