How to avoid failing an emission test

It’s not that anyone wants to fail an emission test. People tend to maintain their cars well; the result is they pass an emissions test with flying colors. Did you know however, that gas caps have a significant impact on whether you pass or fail this test?

In the early days of the automobile a cap was placed on the fuel tank simply to keep dirt and water out. Anything would do the job, including a cork. As vehicles became more sophisticated so did the gas caps, they were vented to let air into the tank so that as the fuel was depleted, the tank would not collapse. These early vented caps also allowed fumes to escape as the fuel vapor expanded on a warm day.

All this changed drastically in 1970 when the EPA was established and the first clean air act was adopted. The industry was given six short years to reduce emissions from cars by 90 percent.

New rules in 1971:

One year after adoption of the clean air act cars were fitted with a device that contained activated charcoal; it captured the fuel vapors when the vehicle was parked. When the car was next started, the vapors were released into the engine where they were burnt. This resulted in a drastic drop in emissions and resulted in considerable savings for the car owner.

New rules again in 1996:

New emission laws were introduced in 1996; the new laws were far more stringent than ever before. The law stated that the car had to be self-testing for vapor leaks from the fuel tank, if there is a leak a warning lamp will show in the vehicle.

Should it be the gas cap that is defective the warning light will go on. In many cases the solution is simple; tighten the cap until it “clicks.” If the cap has failed it’s far better to buy a replacement than fail the emission test.

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