What Does It Mean When Your Jeep Says Gas Cap?


Thanks to the on-board diagnostic system on most vehicles today, you will identify issues with your vehicle before they exacerbate. 

If your engine has a problem, the engine light comes on, and you can take your car to the mechanic before driving any further. 

The diagnostics system also monitors the gas cap, and when there is a problem, a gas cap warning message shows up. 

But what does this message mean?

What Does It Mean When Your Jeep Says Gas Cap? 

The gas cap warning message in your Jeep comes on if it is not secured, missing, or clogged with grime or there is extra pressure on the gas cap due to an issue with the fuel tank. If anything passes through the gas cap, the warning message will come on

The function of the gas cap is to ensure that fuel is well sealed in the fuel tank. 

This ensures there are no leaks and dust and debris do not get into the tank. 

The cap also forms part of the Jeep’s Evaporative Emission System (EVAP) system that ensures that fuel vapors do not escape from the fuel tank and pollute the environment. 

If you have driven your car for about 50,000 miles or longer, the gas cap might be old and weary. 

Such a gas cap might let in pollutants into the fuel chamber of your engine and result in a clogged filter. 

When the fuel supply to the engine is interrupted, the engine light comes on. 

In most cases, the gas cap is only out of position and there is no danger in that. 

You may only need to re-cap it into position and start driving. 

If the gas cap message is still on even after re-capping it back on, then you will need to see a mechanic or replace the cap. 

What are the Functions of a Gas Cap? 

The gas cap is the lock to the fuel chamber. If this cap is not properly fixed, the engine might suffer performance problems and issues with the EVAP system. 

For starters, the fuel cap ensures there is a vacuum pressure seal in the fuel chamber. 

This ensures that the fuel is able to flow with ease through the fuel system as it is pressurized. 

When you tightly secure the cap, you create a vacuum seal. 

Pressurization then ensures that the fuel pump is able to send fuel to the system as needed. 

Further, when it is tightly sealed, the cap ensures that no pollutants and fumes can leak from the fuel tank. 

The EVAP system ensures that drivers and passengers will not inhale toxic fumes while in the vehicle. 

This system also protects the atmosphere from the fumes. 

Your gas cap also ensures there is no dirt or debris in the fuel tank, which may cause corrosion and sediment in the fuel system. 

It also keeps out moisture, which can cause rust in the tank. 

If the fuel cap is missing, damaged, is loose, or too tight, it will not perform one of these functions and the engine detects and sends a message. 

Can I Drive with a Gas Cap Warning Message On? 

It is advisable that you check the gas cap immediately when the light comes on. 

If the cap is missing or is loose, there may be a leak from the gas chamber, and this can pose serious danger to the driver and other passengers. 

If the gas cap damage doesn’t cause a leak, then you will notice reduced engine performance. 

You may also smell gas in your cabin. 

While this does not cause any obvious danger to you at the moment, they will cause damage to your engine and to your respiratory system with time. 

If the EVAP system fails, the quality of air in your Jeep deteriorates. 

The engine will release hydrocarbons, which are harmful to you and to the environment. 

Further, your Jeep’s fuel efficiency reduces significantly. 

How Do You Solve Gas Cap Problems? 

The gas cap problem is easy to fix in most cases. 

You do not need any special skills to fix a loose gas cap or replace an old cap that won’t keep fumes in the gas chamber. 

The first thing you need to do is turn off the engine and then open your Jeep’s gas cap door. 

With a Jeep, there is a depressed section near the door where you need to slip in your fingers and pull the door open. 

Once open, you can see the gas cap.

Inspect the gas cap for any obvious signs of damage. 

Check whether there is a tear, crack, chips, or if the seal between the cap and the filler tube is missing. 

If there is damage that can cause a leak, then replace the cap. 

If the cap is missing altogether, you need to replace it immediately.

However, the cap may have no damages and may not be missing. 

In such a case, open the cap and close it, ensuring it is well in position. 

When replacing the gas cap, ensure that you do it properly so that you do not leave it out of position again. 

Ensure the threads sit and seal as they should on the filler tube. 

Turn your cap until you hear it click three times. 

After replacing your gas cap, check if the engine light is still on when you drive. 

In most cases, you will have solved the problem. 

If the steps above do not help, you need to see a mechanic for further diagnostics. 

There are cases where dust and debris in the fuel chamber causes the gas cap warning message to come up. 

In such cases, the mechanic should help you clean the fuel tank to unclog the fuel system filter. 

If the problem is simple, and you do not need to replace the gas cap, keep monitoring the cap for signs of wear and tear. 

The cap needs replacement once in a while. 

Avoiding The Gas Cap Message

You can avoid the gas cap message by:

  • Ensuring the gas cap is in position after you refuel
  • Listen to the gas cap and ensure it clicks when you close it 
  • Keep the area around the gas cap clean so that dirt and grime do not break the vacuum seal of your cap
  • Check that the gas pump is in position when you refuel 
  • Always close the gas cap door to ensure the cap doesn’t disappear

Picking the Right Gas Cap for Your Jeep

You do not have to wait until your gas cap fails for you to replace it. 

If you suspect your gas cap has a problem, you can take it to the mechanic for a test. 

The smoke test uses a smoke machine to test whether the gas cap has any cracks or any loopholes that can cause a leak. 

The most important factor to consider is the fit of the gas cap. 

You need to test the cap to ensure it fits snugly on the gas tank spout. 

If after installing the cap the light goes off, then you have yourself the right gas cap. 

You can also buy a locking gas cap to protect your fuel from thieves. 

However, if you can only release the fuel cap door from inside the Jeep, then you do not need to buy a locking gas cap. 

With most Jeeps, you can access the gas cap door by slipping your fingers and opening the door.

Newer models may even open the gas cap door when opening the trunk. 

If you live in an area where thieves siphon fuel out of parked cars, you should get a locking gas cap. 

Some gas caps may be green and others yellow and others black. 

Most gas caps are black and this is an indication that the engine runs on gas with less than 10 percent ethanol. 

If your gas cap is green, then your engine runs on diesel and if you have a yellow cap, then your engine runs on gas with between 15 and 85 percent ethanol. 

It is good to replace the cap with one of the same colors in case you sell your Jeep and someone needs to know what kind of gas to use. 

Closing Thoughts

Jeeps have a strong brand reputation. 

They have had their popularity as the ultimate off-road vehicles since the first days as military vehicles. 

Today, people see Jeeps the same. 

The design of the Jeep makes it look rugged and reliable. Truth to the look, Jeeps have impeccable off-road driving and towing capabilities. 

When you need a car to take you through a beaten path or through mud or ice, a Jeep is an ideal choice. 

Even with their high levels of reliability, they suffer minor issues, such as a loose gas cap like all other vehicle makes.

If that happens to your Jeep, it is advisable that you check the problem immediately and find a solution. 

John Nelson

You can find John stringing a hammock from the back of his SUV to a tree camping in the outdoors most weekends during warmer weather. John loves the outdoors and the freedom four-wheel-drive vehicles offer.

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