Which statement correctly describes when a fuel cap functional test is required?

Which statement correctly describes when a fuel cap functional test is required?

• A. It is optional and never required even with a cap adapter.
• B. It must be performed on all vehicles if a cap adapter is available.
• C. It must be performed only on diesel vehicles if cap adapters exist.
• D. It should be performed only after a failed smoke test.

Answer: (B)

Ensuring the fuel cap seals properly is key to the evaporative emissions system. When a cap adapter is available, the fuel cap functional test should be performed on every vehicle to verify the cap seals correctly and to catch any cap that could leak vapors. This is why the correct approach is that the test must be done on all vehicles if the adapter is available. It isn’t optional, it isn’t limited to diesel vehicles, and it isn’t something you only do after a failed smoke test—the cap test is part of the standard EVAP checks, regardless of smoke-test results.

Ensuring the fuel cap seals properly is key to the evaporative emissions system. When a cap adapter is available, the fuel cap functional test should be performed on every vehicle to verify the cap seals correctly and to catch any cap that could leak vapors. This is why the correct approach is that the test must be done on all vehicles if the adapter is available. It isn’t optional, it isn’t limited to diesel vehicles, and it isn’t something you only do after a failed smoke test—the cap test is part of the standard EVAP checks, regardless of smoke-test results.