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The Four Symptoms of a Bad Toyota Sienna Fuel Tank Cap

The fuel tank cap in your Toyota Sienna is a simple but very important device. If problems develop with it, you run the risk of decreased engine performance, fuel wastage, and poor gas mileage. You should check your fuel tank cap for proper function every time you visit the gas station. These are the four symptoms you ought to know about bad fuel tank caps.

The scent of gas

Gasoline is a volatile material that when exposed, it usually travels quickly in the air. The most evident sign of a fuel tank cap that has been tampered is a lingering smell of gasoline. An improperly sealed gas cap can cause this. However, this doesn't happen frequently. Be sure to check other parts like the gas tank or the fuel line for leaks.

Low mileage

Again, due to the highly volatile nature of gasoline, it evaporates very easily. If your fuel tank cap is leaking gas or is not sealed properly, the fuel in your tank may evaporate at a surprisingly alarming rate. If you notice a sudden decrease in fuel efficiency and you couple that with the strong smell of gasoline hovering in and around your vehicle, check your fuel tank cap and other fuel related parts.

"Check engine light" is on

Normally, vehicles like your Toyota Sienna are equipped with a check engine light that may illuminate for a myriad of reasons. Figuring it out will be a tough nut to crack. One of the obscure causes for this light to come on could from a defective fuel tank cap.

Impure emissions

Cars that drive around with a bad fuel tank cap may emit harmful waste products such as smog. Smog is a mixture of unburned fumes that aren't properly combusted and filtered through the engine and exhaust systems. A bad fuel tank cap may contribute to this problem because openings in it may allow contamination of the fuel. Once the fuel becomes contaminated with foreign material, the combustion process might get disturbed. For one, water could get into the engine through a fuel tank cap with a damaged seal. This will usually form a misfire. Over time, repeated misfires will cause permanent damage to your engine.

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  • Four Tips on Prolonging Your Toyota Sienna Fuel Tank Cap's Life 27 February 2013

    The fuel tank cap in your Toyota Sienna is more important than it looks. Although very simple looking, it has a lot going under its belt. A fuel tank cap provides a number of critical functions with regards to safety and efficiency. A fuel tank cap prevents gasoline from exiting the gas tank in the form of fumes. A gas cap also seals the tank and protects the fuel from outside contaminants that may harm the tank and the engine. By doing this, it helps to keep gasoline flow under pressure to make gasoline flow easily into the engine. As you can see, the fuel tank cap is extremely significant and maintaining it is top priority. Here are some tips on how to do it.


    Clean the fuel tank cap.


    Fuel tank caps are susceptible to dirt and grease. This can sealing and unsealing it hard to do. But perhaps the biggest hazard is the fact that a dirty fuel tank cap might leave some residue behind, and drop some of that into the tank. If that happens, Spray a petroleum-based lube all over the screwing mechanism on the gas cap. This lube makes a great cleaner, and it will dissolve any dirt on the gas cap. Wipe it off clean. Afterwards, cover the cap completely with a silicone-based spray. Petroleum-based lube will eventually degrade the fuel tank cap if it is not removed properly. Covering the cap with a silicon spray lube will protect it from wear and tear.


    Diagnose error codes.


    Once the check engine light goes up, it's time to pull out your diagnostic scanner. One common error code that you may encounter upon scanning is "P0440", which indicates a loose fuel tank cap. However, this is not the only code involving the fuel tank. Other codes will typically be in the "P0400" series. Some of them could indicate something worse than a loose gas cap, such as a broken seal or even a leak in the gas tank.


    Defrost the fuel tank cap.


    If you find yourself unable to open the fuel tank cap due to freezing, you might want to take this advice for make defrosting the fuel tank cap. Carefully pour warm water on the fuel tank cap. Then scrape away the slush from around the fuel tank cap. This should get rid of most of the ice that holds the cap closed. When water isn't enough, you can use a hairdryer to quickly thaw the ice. To prevent future difficulties, spray some nonstick cooking spray around the seal of the gas cap.


    Tether the fuel tank cap.


    Tethering the fuel tank cap is great for detachable caps. Since the fuel tank cap no longer needs to be set down on surfaces that carry debris, the fuel tank won't be in danger of being contaminated. Tethering also helps prevent gas theft. Installing a tether to a fuel tank cap is easy to do. Just drill a hole on the center of the cap, attach the tether and then anchor it to the body of the car.