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Symptoms Of Bad Gas Cap: Fixed & Revealed (Guide)

Last Updated on July 5, 2023 by Chase Manhattan

The gas cap may seem like an insignificant part of your vehicle, but it plays a crucial role in maintaining the efficiency and performance of your car. In this comprehensive guide, we will explore the various symptoms of a bad gas cap, the reasons behind its deterioration, and how to fix it. Furthermore, we will discuss the potential dangers of driving with a faulty gas cap and the lifespan of this essential component.

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Why Do Gas Caps Go Bad? header image

Can A Gas Cap Go Bad?

Yes, a gas cap can go bad over time. This seemingly simple component is responsible for sealing the gas tank, preventing dust, debris, and water from entering the fuel system, and maintaining the fuel system pressure. A gas cap is typically made of plastic or rubber, and constant exposure to harsh environmental conditions can cause it to wear out, crack, or lose its sealing ability. When this happens, it can compromise the performance of your vehicle and even cause damage to other parts of the fuel system.

Why Do Gas Caps Go Bad?

There are several reasons why a gas cap can go bad, such as:

  1. Wear and tear: Gas caps are frequently removed and replaced every time you refuel your vehicle. This constant usage can lead to wear and tear on the gas cap’s threads and sealing components.
  2. Environmental factors: Exposure to harsh weather conditions, temperature fluctuations, and corrosive elements can cause the gas cap’s materials to degrade over time.
  3. Physical damage: Accidents or mishandling of the gas cap can lead to cracks or damage that can compromise its sealing ability.

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Faulty Gas Cap Symptoms

A faulty gas cap can manifest in ways including:

  1. Cap does not tighten properly: A common symptom of a bad gas cap is when it no longer tightens correctly. Most gas caps click once they are sufficiently tightened. If the cap does not click or pops loose again, it may need to be replaced.
  2. Fuel smell from the vehicle: Another symptom of a bad gas cap is a fuel smell from the vehicle. If the gas cap seal becomes damaged or worn, it may cause fuel vapors to leak from the filler neck, resulting in a gasoline odor.
  3. Check Engine Light comes on: An illuminated engine light can indicate a faulty gas cap. The gas cap is a part of the vehicle’s evaporative emissions system and can cause problems if it is not sealing properly. An improperly sealing cap may cause an evap system leak, which will trigger the Check Engine Light.

How To Tell If A Gas Cap Is Bad

To determine if your gas cap is bad, you should:

  1. Inspect the gas cap: Regularly inspect your gas cap for visible damage, such as cracks, worn threads, or a damaged seal. If you notice any of these signs, it’s time to replace your gas cap.
  2. Check for fuel odors: If you smell gasoline near your vehicle, it could be an indication that the gas cap is not sealing properly, and fuel vapors are escaping.
  3. Monitor the Check Engine Light: If your Check Engine Light comes on, have your vehicle’s computer scanned for trouble codes. If the codes point to an issue with the evaporative emissions system, your gas cap could be the culprit.

Notes Worth Mentioning

It’s worth mentioning that the gas cap is part of the EVAP system. There’s always the potential of there being a greater issue at hand there. A bad gas cap will present itself as a faulty purge valve, so it’s recommended that you test the purge valve as well if a new gas cap does not fix the issue. If your tests are inconclusive, it’s easy enough to clean a purge valve in search of a potential quick fix.

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How To Fix A Bad Gas Cap Header Image

How To Fix A Bad Gas Cap

Fixing a bad gas cap usually involves replacing it with a new one. To do so, follow these steps:

  1. Locate the gas cap on your vehicle. It is usually found on the top of the gas tank or on the side of the vehicle near the gas tank.
  2. Remove the old gas cap by unscrewing it.
  3. Install the new gas cap by screwing it onto the filler neck.
  4. Tighten the gas cap until it clicks or feels snug. Be careful not to overtighten, as this can cause damage to the threads or the sealing components.

Related Info for Bad Gas Caps header image

Can A Bad Gas Cap Cause Hard Starting?

A bad gas cap can cause hard starting in some cases. If the gas cap is not sealing properly, it can allow air to enter the fuel system, which can lead to a lean fuel mixture. This lean mixture can make it difficult for the engine to start, especially in cold weather. Additionally, a bad gas cap can cause a drop in fuel pressure, which can also contribute to hard starting conditions.

Is It Bad To Drive With A Bad Gas Cap?

Similar to driving with a bad purge valve, driving with a bad gas cap is not advisable, as it can lead to several issues, such as:

  1. Decreased fuel efficiency: A faulty gas cap can allow fuel vapors to escape, which can result in decreased fuel economy.
  2. Increased emissions: Since the gas cap is a part of the vehicle’s evaporative emissions system, a bad gas cap can lead to increased emissions and potential environmental damage.
  3. Damage to other components: A bad gas cap can allow contaminants to enter the fuel system, potentially clogging fuel injectors, fuel filters, and causing issues with other components in the fuel system.

How Much Does It Cost To Fix A Gas Cap On A Car?

The cost of fixing a gas cap on a car depends on the make and model of your vehicle and whether you choose to purchase an original equipment manufacturer (OEM) or aftermarket replacement. Gas caps typically range in price from 50. If you choose to have a professional mechanic replace the gas cap for you, labor costs may add an additional 50 to the total expense.

How Long Do Gas Caps Last?

The lifespan of a gas cap can vary depending on several factors, such as the quality of the materials used, exposure to environmental conditions, and proper maintenance. On average, gas caps can last up to 50,000 miles or around five years. However, some gas caps can last longer with proper care and attention.

In conclusion, the gas cap is a small but vital component of your vehicle’s fuel system. Regular inspection and maintenance can help you identify and fix any issues with your gas cap, ensuring optimal performance and fuel efficiency. Remember to replace a faulty gas cap promptly to avoid potential damage to your vehicle and the environment.

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