Check Fuel Cap – What Does It Mean? How to Fix?

It can be alarming to see the “Check Fuel Cap” message appear on your car’s dash. What do you do? What does “Check Fuel Cap” actually mean?

This Check Fuel Cap message indicates that the fuel cap has not been properly affixed onto the fuel tank filler tube, the fuel cap is missing from the filler tube, or the fuel cap is damaged.

These three issues will prevent the fuel cap from serving one or more of its many purposes.

If your fuel cap indicator light is on, it means that the car’s computer system has detected a leak. Most often, a loose gas cap is a culprit. If the fuel cap itself is not the problem, it means that there is a leak somewhere in the system and triggered the fuel cap indicator light to turn on.

If you check and the fuel cap looks okay, have a mechanic check the issue so he can pinpoint the issue.

Read on to find out more about what the Check Fuel Cap indicator light means and how to fix this issue.

“Check Fuel Cap” Light Meaning

check fuel cap

When the check fuel cap light goes on, a leak has been detected by your car’s computer. Usually, your fuel cap is loose, and if it is, tightening your gas cap will solve this. If the cause is not a loose fuel cap, have a mechanic check the issue.

Your fuel cap plays a vital role in your car’s fuel system as it prevents fuel evaporation and contamination.

Sometimes a leak somewhere in the system can trigger the fuel cap indicator to light up. Whatever the reason is, if your fuel cap indicator light goes on, do not ignore it.

You’ll notice that when the fuel cap indicator light is on, there will be a reduction in your engine performance, even if it is a very slight one.

Your engine will need to work a bit harder, and most likely, your gas mileage will slightly diminish, and you will be releasing toxic gases into the environment.

Where Is Your Fuel Cap Located?

Whether you’re driving a rental or brand-new car or truck, it has happened to many of us when you don’t know which side your gas cap is on. So, how do you know which side it is on?

Your car will have a fuel pump icon on your dashboard. It will usually have a bold arrow pointing either to the left or right side of the pump. This indicates which side your fuel cap is located on.

Some cars do not have this arrow. What you need to do is check the icon and see where the fuel handle is located. If the handle is on the right, your gas cap will be located on the right side of your car.

Note that the fuel pump icon’s position is not an indication of where your gas cap is located. Newer model cars will have the arrow as an indication of the location of the fuel cap.

Signs of a Faulty Fuel Cap

1. Fuel Cap Does Not Tighten

The easiest issue to spot with a faulty fuel cap is a cap that does not tighten. You will notice that fuel caps are designed to click when they are properly tightened.

If your gas cap doesn’t click when you tighten it, it needs to be replaced. Sometimes, it will click but will come loose again. This, too, is a sign that it needs a replacement.

2. You Smell Fuel Vapors

It’s normal to smell fuel vapors when you’re gassing up. But when you’re in your vehicle and haven’t recently loaded gasoline, and you get a fuel smell, it may be a symptom of a leaking fuel cap. Check the seal of your fuel cap, as it may be damaged.

3. Your “Check Engine” Light Goes On

When your Check Engine light goes on, a possible cause is your fuel cap. Your fuel cap is part of the evaporative emissions system of your car.

If your gas cap is not working properly, it can cause a leak in the system and allow the fuel to evaporate. This problem can trigger the Check Engine light to go on.

The fuel cap may seem to be a small issue and won’t really cause major issues on your car’s overall performance. However, if the Check Engine light goes on because of that issue, your car won’t pass the emissions test. If you suspect your fuel cap is the issue, replace it immediately.

What Causes the “Check Fuel Cap” Indicator Light to Turn On

When you have a loose or faulty fuel cap, fuel evaporation takes place and can, in the long run, interfere with the functioning of your engine system. There are various causes of why your indicator light turns on.

These are some of the reasons:

1. Your Fuel Cap

The most common reason is a loose-fitting or faulty fuel cap. The fuel cap is a simple but vital car part. Its role is simple. It seals the fuel in the tank and stops it from evaporating. The fuel cap plays an important part in the evaporative emissions system of your vehicle.

A fuel cap helps you reuse the fuel vapors that would otherwise only be emitted into the environment.

Check that your fuel cap tightens securely every time you close it. Check also for cracks and leaks. Even a tiny crack can make the fuel cap indicator light up. If you have a faulty fuel cap, replace it immediately.

2. Your Catalytic Converter

Your catalytic converter can be located underneath your car, near the exhaust outlet. The catalytic converter’s purpose is to change the toxic and harmful substances that come from your car’s exhaust into less harmful substances.

The converter changes substances like nitric oxide, carbon monoxide, and nitrogen dioxide into carbon dioxide and water vapor before released into the atmosphere. If you notice that your gas mileage has reduced, have a mechanic check your catalytic converter.

3. Your Fuel Filler Neck

The fuel filler neck is the basic entry point for fuel in your car. It serves to bring fuel from the nozzle of the gas pump into your fuel tank. Sometimes, a crack in the fuel filler neck causes the gas to leak.

No matter how often you tighten or even replace your fuel cap, if the culprit is a crack in the fuel filler neck, that fuel cap indicator light will still keep turning on. Have a mechanic check your fuel filler neck if your fuel cap light keeps turning on.

How to Reset the Fuel Cap Indicator Light?

  1. Turn off your engine. Push the button in your car that fuel cap door if there is a button in your car. If your fuel cap door needs a key, use your key to open the door;
  2. Open the fuel cap door;
  3. Check to see that the fuel cap is tightly on. Remove fuel cap and seal tightly;
  4. Close the fuel cap door; and
  5. If your fuel cap indicator light remains on, use an OBD-ii code scanner. (This is a diagnostic system that is included in every vehicle produced after 1996)

Note: It may take several minutes for your indicator light to turn off after replacing your fuel cap. If your indicator light keeps turning on and then goes off after you tighten the fuel cap, you have a loose or cracked fuel cap, and it may need to be replaced.

How to Clean the Fuel Cap?

Cleaning your fuel cap is just as important as cleaning your car itself. Your fuel cap is susceptible to grease and grime accumulation. Sometimes, when your fuel cap gets really dirty, it can lead to a blocked fuel pump or gas filter.

Here’s how you can clean your fuel cap:

  1. Remove the fuel cap from your fuel tank. Lay it on a table lined with layers of old newspapers. It will be oily and greasy, and you don’t want to stain a good table;
  2. Use a petroleum-based lube to clean the screwing mechanism of your fuel cap;
  3. Spray or apply the petroleum-based lube generously over the screwing mechanism;
  4. Leave on for a few minutes, and then use a rag to wipe it all off. The lube will dissolve the grease, and when you wipe it off, the grease will come off with the lube;
  5. If you notice any dirty spots left after you wipe them off, spray that part with the lube again and repeat the process;
  6. Use a silicone-based spray to cover your fuel cap completely. Petroleum can degrade the quality of plastic but spraying it with a silicone-based spray after can restore the quality of the plastic at the same time protecting it from wear and tear; and
  7. Screw back your fuel cap. Make sure that it is properly put on and tightened.

Again, what does Check Fuel Cap mean? The Check Fuel Cap message indicates that:

  • The fuel cap has not been properly affixed onto the fuel tank filler tube,
  • The fuel cap is missing from the filler tube, or
  • That the fuel cap is damaged.

These three issues will prevent the fuel cap from serving one or more of its many purposes.

How Long Does a Fuel Cap Last?

The role of your fuel cap is to keep dirt and water away from the fuel stored in your gas tank. Having clean fuel is vital to run your vehicle and provide the necessary material for the combustion process.

Your car’s fuel cap goes on top of the filler neck and seals it off to keep out dirt and water. The fuel cap is frequently used, and the wear and tear will mean that you will, eventually, need to get it replaced.

Your fuel cap will usually last anywhere from 40,000 to 50,000 miles, depending on usage. If properly cared for, however, it will last longer. It is vital to regularly clean and check your fuel cap for it to last longer.

Some studies show that a defective fuel cap can cause up to 114 liters of fuel to evaporate yearly.

Different Kinds of Fuel Caps

Yes, there are different types of fuel caps. Knowing what they are can make it easier to get a replacement when one is needed.

Vented Fuel Caps

These fuel caps were commonly used by cars that car companies manufactured before 1985. These caps come with a valve that makes it possible to release pressure when it becomes too high.

Non-Vented Fuel Caps

what does check fuel cap mean

These fuel caps are commonly found in cars produced after 1985. Car companies produced these caps to keep the integrity of your car’s fuel system. They don’t allow the release of fuel pressure from the system, required by the emission control regulations.

Is It Safe to Drive with the “Check Fuel Cap” Light On?

Your dashboard has many warning lights to alert you of the condition of your vehicle. Some lights alert you of serious problems, and some lights give information. The Check Fuel Cap light provides information.

It is telling you that your fuel cap is either loose or is completely missing. The best thing to do is to check it and see what the problem is. If you have checked and the alert light is still on, is it still safe to drive?

Yes, you can still drive with the Check Fuel alert light on. You need to know that driving with the fuel cap light on will not harm your engine. Driving with your fuel cap light on will not immediately cause you to lose fuel.

Your car’s gas tank has a flapper valve that stops fuel from spilling if the fuel cap is missing.

The danger here lies in having an ignition source like a lit cigarette come close enough in contact with the fumes escaping from the gasoline tank. So, if your Check Fuel light goes on, you can still drive your car, but you will still need to act on the problem.

Conclusion: Fuel Cap Check – What Does It Mean? How to Fix

The Check Fuel Cap message indicates that the fuel cap has not been properly affixed onto the fuel tank filler tube, the cap is missing, or it is damaged.

Because of this, the car’s computer system has detected a leak. Your gas cap most probably has not been screwed on properly. You’ll need to check if it is properly closed or if it has cracks.

If the fuel cap itself is not the problem, it means that there is a leak somewhere in the system and triggered the fuel cap indicator light to turn on. If you check and the fuel cap looks okay, have a mechanic check the issue so he can pinpoint the cause at the soonest possible time.

Again, it might be worth your time to check the following in case there’s no problem with your fuel cap:

  1. Your Catalytic Converter
  2. Your Fuel Filler Neck