As you may know, your car pumps liquid gasoline from the fuel tank to the engine to be ignited by the spark plugs. Your car may also contain some gasoline that has evaporated which is then sent to the engine to be used up. The evaporated gas gets collected in a separate tank called the charcoal canister. Once certain driving conditions are met, a valve opens to the engine and the fuel vapors get mixed in with the rest of the fuel being burned.
In order for this fuel system to work properly, it needs to be sealed from the outside air so that nothing escapes. Most fuel caps have a rubber O-ring to prevent vapors escaping when the cap is secured. As you drive, your car is able to monitor the system for any possible leaks in the system and display a warning light on the dashboard if a leak is detected.
What the fuel cap indicator means
Simply put, if your fuel cap light is on, it means that the computer has detected a leak in the system, typically from a loose gas cap. If this light comes on while driving, pull over in a safe spot and re-secure the cap. Continue driving normally with the light illuminated and it should go off within a day or two. If the light doesn’t turn off, inspect the gas cap for any damage and replace it if necessary.
A leak present somewhere else in the system can also trick the computer into thinking the gas cap is leaking. If the gas cap looks okay and the light does not turn off, have a certified technician investigate the issue and determine the cause.
Is it safe to drive with the fuel cap indicator on?
The main thing you may notice if the light is on is a slight reduction in performance. With less power, your engine has to work harder to get up to speed. As a result, your gas mileage will diminish slightly. On top of that, you are likely releasing harmful gases into the environment.
Without properly working EVAP systems in every car, our quality of air would be much worse due to the hydrocarbons released from the gasoline. Maintaining your EVAP system also ensures that you are getting the most out of the fuel you buy.
Our certified technicians are always available to assist you with diagnosing any problems related to your fuel cap indicator light.
This article originally appeared on YourMechanic.com as What Does the Fuel Cap Warning Light Mean? and was authored by Spencer Cates.