Why Is a Loose Fuel Cap a Real Problem?

March 30,2015


One of the most common and often most easily addressed car problems is the loose fuel cap. In 2010, loose fuel cap repairs made up 9.28 percent of all car repairs, according to statistics gathered by CarMD, an automotive diagnostic tool manufacturer. This fact, along with the very low cost of fixing the problem, means that the fuel cap is one of the first things that you should check when your check engine light goes on.

Why is a loose fuel cap a problem, then? It’s because it allows gas from the fuel tank to evaporate and therefore causes the car to have lowered fuel mileage than it would have with a tight seal. Additionally, any opening to the fuel tank allows hydrocarbons to vent into the atmosphere. This is a health and environmental concern, and it’s why automotive fuel systems have been regulated closed since the 1970s. To make sure they remain closed, vehicle fuel systems in cars manufactured over the last four decades have been programmed to trigger the “check engine light” when the fuel cap is loose or any other leak within the fuel system occurs.

Another function of a closed system is to assist the fuel pumps by allowing pressure to build within the fuel tank. Within a pressurized system the pumps do not have to work as hard and they last longer over time. The other parts of the fuel system that can leak, including vacuum lines, a purge valve, and a vent valve, could cause the check engine light to go on, but human error makes it far likelier that a loose fuel cap will be the culprit. If you need help remembering to tighten your cap after a fuel up, caps make a clicking noise to signal they are closed. Make it a habit to count to three clicks before you close the fuel door. At three clicks, it’s definitely tight and you shouldn’t have to worry about it.

Your car’s manufacturer included dashboard lights for a reason, which is ultimately to help you keep your car in great shape. So it’s advisable to check with your mechanic if that light comes on or if you have noticed lowered gas mileage. While tightening a fuel cap is a “repair” you can easily make yourself, if you do so and your check engine light remains on, Veenstra’s would be happy to help you solve this problem and make sure your car stays in top driving condition.