Audi Fuel Cap

Diagnosing a Loose Fuel Cap in Your Audi

by admin December 1, 2019

Your Audi is the representation of decades of motoring research and refinement, meaning that when you hit the road, you are more intune with your vehicle than ever before, leading to breathtaking driving experiences. However, faults with simple systems, such as you fuel cap, can ruin this motoring ideal, which is why in this article, we will be exploring this issue further.

What is the fuel cap?

Also called the gas cap or fuel filler cap, the fuel cap is a very simple but essential part of your Audi. It prevents contaminants such as dust or dirt from getting into your gas tank. It also acts as a seal and a barrier to prevent gas fumes from leaking out also. Think of it like the lid on a soda bottle. It keeps dirt and dust out, but also keeps the liquid and the bubbles in.

Don’t Rush at the Pumps

We have all had days where we are late on the school run or we are late for work. Sometimes we are preoccupied when we are at the pumps, simply refuelling on autopilot. However, forgetting to properly reseal your fuel cap is a common issue and is the leading cause of gas cap issues! This lapse of concentration can result in worrying signs of a check engine light and is completely avoidable. So next time you are at the pumps, spare a moment to make sure your fuel cap is secure before driving off.

Safety Hazard

A loose fuel cap will mean that fuel is able to be lost through evaporation. Like the fuel itself, these vapours are highly flammable, and given the right circumstances or severity of the leak, these vapors could ignite, causing serious harm to yourself and others, particularly if you park your vehicle in a garage. Even when outside, a loose fuel cap is still harmful, as it allows the vapors to escape into the air. This will cause smog when it hits the ozone layer.

Symptoms of Fuel Cap Failure

There are several signs and symptoms of fuel cap failure which can impact the overall performance and safety of your Audi such as:

1. No Click

When returning your fuel cap after refuelling, you should also hear an audible click. This noise tells you that the cap is tightly affixed. If you don’t hear the click, then it is either because you haven’t tightened it enough or the cap has been damaged and will need replacing ASAP.

2. Fuel Smell

You should never be able to smell fuel from your vehicle. If you do, this is always a worrying sign. This often indicates that your fuel cap seal is damaged, meaning that the vapors are leaking.

3. Reduced Fuel Economy

Because it will allow fuel vapors to leak, a loose fuel cap can also quite significantly reduce your fuel economy. It’s amazing to think that a few seconds of time to check it is fitting can result in such an expense.


Aside from you noticing the symptoms, your Audi is also designed to detect fuel cap problems. Since 1996, all vehicles have been fitted with EPA-certified sensors, which trigger when fuel vapors are detected. This helps reduce air pollution and keeps you and your passengers safe. When it detects an issue, it will instruct your vehicle’s onboard computer to illuminate the check engine light as well as provide you vehicle with a diagnostic trouble code that signals an emission leak.

Older vehicles can also detect emissions leaks but with reduced efficiency. They will usually only illuminate the check engine light minus the exact trouble code. However, this is more than enough of a warning, as all competent drivers know that a check engine light should never be ignored. Check engine light illumination can also be a sign of much more serious and potentially dangerous problems with the engine or its associated systems. Therefore, if you want to avoid expensive part failures, lengthy repairs, and the increased risk of accidents, you should take action immediately.

McIlvain Motors

McIlvain Motors of Chandler, Mesa, Audi Loose Fuel Cap Issue Check Phoenix, Scottsdale, and Tempe, AZ are a friendly team of dedicated and experienced technicians who are always happy to help you with your vehicle. No matter how big or how small the issue may be, we will have our expert technicians resolve it for you. We are Audi specialists and have combined 100 years of automotive experience. Call us today or come by for a consultation. We look forward to meeting you and becoming your trusted Audi service and maintenance specialists.