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What Problems Can a Loose Gas Cap Cause for Your RV?

Are you wondering what problems can a loose gas cap cause?

It would be awesome if every part of an RV stayed just like the day that you bought it.

But they don't.

Even high-end RVs eventually wear down. And one thing that goes quite often on any RV is the gas cap.

So what problems can a loose gas cap cause you and your RV?

What Problems Can a Loose Gas Cap Cause?

After talking with my mechanic, my mother, and Google (in that order), I learned that a loose gas cap can cause three main problems for your vehicle.


First, it causes an engine light to come on. This is bad if you need an emissions test, but can also hide other, more serious, problems with your engine.


Also, if you've been smelling gas lately, it may be thanks to a loose gas cap.

Thirdly, it can cost you money in lost mileage.

Here's What Happens When You Have a Loose Gas Cap

white RV

Image by campingbil from Pixabay 

We've all been there at one point.


We're driving along when suddenly the engine light flicks on, and then we start to panic.

Oh no! We think to ourselves. I can't afford to fix anything right now!


Good news! When that engine light comes on, it's not always something horrible. In fact, the most common reason your engine light is on is because of a loose gas cap.


That's a good thing because it's easy and relatively cheap to fix a loose gas cap. Best of all, you can do it yourself. But you should absolutely fix it.


Delaying will cost you money. Face it, you're going to have to fix it anyways. And like everything in your RV, responsible ownership means keeping it well maintained, even if it's only a loose gas cap.


And there's more.


You see, a loose gas cap will cause your engine light to turn on. But that can also hide other, more serious issues. If you're convinced that the engine light is on because of a loose gas cap, then you may not notice that your fuel pressure valve is failing, or you're about to lose your alternator or any number of other mechanical problems.

So always fix things as soon as you're aware of them.

If you want to know what problems can a loose gas cap cause, then let's get to it.

Your dashboard yells at you


No doubt about it, the number one cause of your RV's engine light turning on is a loose gas cap.

Ask yourself this: where were you when you first noticed the light was on?

Chances are it was while driving, and often after pulling away from a gas station.

That's because there's a sensor in your fuel system which measures the vacuum pressure inside the gas tank.

If it detects a change in air pressure thanks to a small leak through the gas cap, it will trigger the engine light.

And you know how that feels. So what should you do?

First thing, take the gas cap off and check to see if it's cracked.

If you can't find any cracks, check the rubber gasket under the gas cap. If it's worn down or cracked, then that would cause a leak.

Next, try putting the gas cap on and turning it as far as you can, until you hear it clicking a couple of times.

Turn your RV back on. Is the check engine light still on?

Don't panic if it's still showing, because chances are you'll need to replace the gas cap.

But the check engine light isn't the only thing a loose gas cap will cause.

Your nose objects


It begins with a smell.

You feel that every time you start your RV, there's engine fumes leaking into the cab.

That's the smell of gas.

When looking for what problems can a loose gas cap cause, the smell of gas is high on the list.

Couple this stench with an engine light and you know what the problem is.

That's because a loose gas cap will leak pressurized fumes out of the gas tank into the air around your vehicle.

And because gasoline fumes are heavier than air, they tend to hover around the ground under your vehicle. When you start the engine, your air system sucks them up and into your RV. Yummy!

Sorry, you can't go that far


What problems can a loose gas cap cause your wallet?

For starters, you'll be filling up a lot more.

Did you know that your RV's engine doesn't actually burn liquid gasoline, but fumes?

It's true!

Your fuel system is finely pressurized to keep those fumes heading in one direction: towards the spark plugs.

The gas fumes pass through the spark plugs, which ignite them and this energy is transferred to the valves.

But a loose gas cap will cause those fumes to vent out of the fuel tank.

Thanks to the pressure in the gas tank, more and more fumes will leak out, and the end result is that you'll need to fill up more often.

So, think you can ignore that engine light? Your bank account doesn't.

The good news is that fixing a loose gas cap costs less than $10.

Your Gas Cap

gas cap

Image by bburnes from Pixabay 

You know what problems can a loose gas cap cause, but before you learn how to fix it, let's take a brief moment to look at what your gas cap actually is.

At its core, a gas cap is a solid piece of plastic with a screw cap that twists onto the gas intake.

There's a rubber gasket around the rim of the gas cap to seal it, keeping the fuel system pressurized.

But there's more.

That's because there are several types of gas caps, and the one you need to look at depends entirely on you.

Locking vs unlocked gas caps


Whether or not your gas cap locks is up to you.

An unlocked gas cap is simple. It screws into your gas intake and unscrews again when you need it. There's not much else to it.

But if you're afraid that someone might siphon gas out of your RV, then go for a locking gas cap. This is a gas cap with a lock on it. It requires a key to unscrew it.

Cool, but mostly unnecessary.

How to Fix a Loose Gas Cap

Fixing your loose gas cap is relatively straight forward. I figured it out in only a couple of hours, and I'm not a mechanically-inclined person.

Now you know what problems can a loose gas cap cause you and your vehicle, you can easily solve the issue.

Just think, no more engine light, no more gas smell, and increased mileage.

Let's get to it.

Step one


This can't be stressed enough. Don't try to eyeball a replacement gas cap. Instead, Google the exact specs of the gas cap on your vehicle, and then find that exact match.

Of course, that doesn't mean you need an exact factory-issued gas cap. But you don't want one that won't let the gas cap door close, or which is too small and continues to leak gas fumes.

So you need one that matches the exact size and width of your factory-installed gas cap.

Most parts dealers will keep an inventory of this for you, and if they don't have your size in stock, they can order it. Amazon is another great place to find gas caps, once you know what to look for.

Step two


Next, you'll want to remove the detention ring.

This is the plastic ring which keeps your gas cap attached to your RV.

Use a pair of needle-nosed pliers and gently slip the ring off the gas cap. Now the old gas cap should be free.

Slip the detention ring over the new gas cap.

Step three


Here's the easy part.

Once you've hooked the detention ring onto your new gas cap, it's ready to go.

Simply screw the gas cap on like you would your old one and wait to hear the familiar "click."

But get this.

Your check engine light won't turn off right away.

You see, the pressure in your gas tank needs to reset now that it's sealed off. If your engine light is still on, try driving a few miles.

Eventually, your fuel system will repressurize and that engine light should turn off.

And you're good to go!

Watch Your Engine Light

What repair could be easier?

Seriously, most RV issues are easily repaired by yourself, once you know what to look for. And a loose gas cap is one of those. It's up there with replacing a windshield wiper when it comes to ease.

Keep an eye on your engine light after you've replaced your gas cap, because if it comes back on again then there could be other things going on that your loose gas cap was hiding.

For instance, if the gas cap housing itself is damaged, then you'll need a mechanic. No gas cap is going to help that no matter how new it is.

Have you ever had to replace a loose gas cap before? Let us know in the comments!

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