Signs of a Broken Gas Cap (2024)

Importance of the Gas Cap

The fuel cap or gas cap on a vehicle contributes to vehicle efficiency and safety, and it helps keep your car performing well. Primarily, it’s intended to create an airtight seal on the fuel tank, preventing fuel vapors from escaping into the atmosphere. It helps to reduce harmful emissions, and it also helps you retain all of the fuel you’ve purchased.

Also, it’s necessary to maintain the evaporative emissions pressure. This system pressurizes the fuel tank and checks occasionally to ensure there isn’t loss of pressure – if there has been a loss of pressure, it indicates a leak that needs to be repaired. If you have an illuminated Check Engine Light, the gas cap can be the reason.

Then, there are the common, well-known reasons for a fuel cap. It protects from dirt and other contaminants from entering the fuel, prevents people from stealing your gas, and it keeps gas inside the tank in the even of an accident to prevent a fire or explosion.

Signs of a Broken Gas Cap

If you have a bad gas cap, symptoms can be wide-ranging, including:

• Check Engine Light – A broken or loose gas cap can trigger the Check Engine Light to come on, as it affects the evap emissions system’s pressure.
• Raw fuel smell – If you notice a strong smell of gasoline around your car, especially near the fuel filler area, it could be due to a damaged or improperly sealed gas cap.
• Poor fuel economy – A faulty gas cap may cause your vehicle to have reduced fuel efficiency, as it can allow fuel vapors to escape, leading to the appearance of increased fuel consumption.
• Difficulty tightening or removing gas cap – If you’re having trouble tightening or removing the gas cap, it could be a sign that the threads or locking mechanism are damaged.

Seldom does a bad gas cap affect how your vehicle performs, so it can go undetected for quite some time – until you need to fuel up again. And if there’s nothing visibly wrong, it’s easy to overlook it as the cause.

Consequences of a Broken Gas Cap

But if your gas cap is broken, there can be consequences to it. It’s a safety concern, since fuel vapors can easily ignite and lead to a fast-moving vehicle fire. It’s a rare occurrence, though.

The main consequence you’ll face is that the Check Engine Light is on. The diagnostic trouble codes (DTCs) are primarily evaporative emissions-related, with codes like P0455 and P0456 present in the onboard computer. Those codes can come up with any evap system leak, though. And with the Check Engine Light already illuminated due to a faulty gas cap, there’s no way to identify if there are any other faults. Left uncorrected, you might be oblivious to an even more concerning problem that needs your attention.

When your fuel cap is missing or badly broken and it doesn’t seal the filler neck, the fumes that evaporate from the tank will add up. Especially if you don’t fill up very often, a noticeable amount could escape into the atmosphere in a week’s time.

Lastly, there is an environmental impact if you don’t check the fuel cap and replace it if it’s bad. It contains hydrocarbons that can contaminate both air and water.

If you suspect you have a faulty fuel cap, we can check the DTCs for you and help narrow down the cause. And when you need a new gas cap, AutoZone can provide the perfect fit to help seal up your fuel system again.

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