Why Your Car Is Leaking Gas


You’re driving along when all of a sudden, you notice the smell of gas inside your vehicle where there was no gas smell before. Such a smell is almost always a cause for concern, as it indicates that there is a fuel leak happening somewhere within your car’s fuel delivery system. 

While the cause of a car gas leak always has to do with the fuel system, there are several components within this system that can cause the leak. You may have a hole in your gas tank, a fuel line that is broken or not connected properly, or old and worn-out fuel injectors.

In this article, we’ll be going over the different components in your car’s fuel system that can cause a leak, how to determine if you have a leak and how to fix one, and other information about car gas leaks that you may want to know.

What Causes a Car Gas Leak?

As we’ve mentioned, car gas leaks are generally the result of an issue with your car’s fuel system. The various parts of your fuel system can fail due to wear and tear, or they can sometimes break prematurely.

Related: How to Start a Car With a Bad Fuel Pump

In any case, properly maintaining your car will help you catch fuel leaks before they get too serious, which will, in turn, decrease the cost of any repair bills you might end up with. If you suspect that your car might have a fuel leak, these are some of the potential culprits:

Broken Fuel Tank

Since the fuel tank is obviously the main reservoir of gas in your car, it’s important to ensure that your fuel tank is always in good condition. To that end, you should periodically inspect it to make sure it isn’t wearing out.

The fuel tanks in most cars are designed to last about a decade before they need to be replaced, but they may wear out more quickly if you tend to drive your car in certain conditions.

In particular, if you live in a moist climate where there is a lot of salt around (for example, if you live near the ocean or in an area where they salt the roads during the winter) then there’s a higher chance that your fuel tank will rust out prematurely.

Holes can appear in your fuel tank if it gets rusty enough, but they can also develop if a piece of road debris gets kicked up hard enough into the tank.

Broken Fuel Lines

Fuel lines, as you may know, are what transports the fuel from your car’s fuel tank to its engine. Your fuel lines can wear out on their own over time, but they can also be damaged by blunt force. Leaks from your fuel lines may also be the result of shoddy installation.

The majority of vehicles currently on the road generally use rubber fuel lines, while newer vehicles sometimes use nylon fuel lines. Rubber fuel lines are more prone to failure as they get old, but nylon fuel lines melt more easily and are harder to repair.

Regardless of what kind of fuel line you have, however, they can be damaged in similar ways. A well-aimed rock kicked up from one of your tires can potentially puncture your fuel line and cause a leak that way. If you manage to high-center your vehicle at any point, this can also be the cause of a broken fuel line.

Lastly, leaks in your fuel line can occur if the fuel line is not properly sealed at one or both of its mounting points. 

Broken Fuel Injection System

The fuel injectors in your car are what actually deliver gas to the engine. The fuel injectors spray a carefully timed and measured amount of fuel into the engine, which ensures that the engine runs as powerfully, smoothly, and efficiently as possible.

The injectors are connected to the fuel lines via the fuel rail, and in between each injector and the fuel rail is a rubber O-ring, which helps maintain an airtight seal between the two components. With time, this rubber can get brittle from the heat coming from the engine, and eventually break. If the nozzle or the body of the injector develops a crack, this will also cause a leak. 

Related: Can You Drive a Car With a Bad Fuel Injector?

How to Tell If Your Car Has a Gas Leak

The most obvious sign that your car has a gas leak is the smell of gas inside the cabin. The fuel system in your car is not airtight as it is, but nonetheless, you should be unable to detect any kind of fuel smell if your fuel system is properly sealed.

Another sign of a gas leak is, as you might expect, a puddle of gas underneath your car. Depending on whether or not you tend to park in the same spot, it can sometimes be hard to determine just by looking if your car is actually leaking anything onto the ground.

  • One way you can check for leaks is to put a layer of something under your car that will catch any leaking liquids, like cardboard, newspapers, or aluminum foil.
  • Not only will this help you determine if your car is leaking, but it can also help you figure out if any fluids other than gas are also leaking out (different types of fluids will have different colors).

You should also take note of your gas gauge when parking your car for the night. If your car is leaking, the gas gauge will show a smaller amount of fuel in the tank when you return to your car the next day, since there will obviously be less fuel still in the tank.

One more sign of a car fuel leak is a rough idle, which is the result of the engine running lean as a result of fuel being lost from the system.

How Much Does it Cost to Fix a Gas Leak in Your Car?

This depends on what part of your fuel system is broken and whether or not you’re fixing your car yourself. Taking your car to a dealership for repairs will obviously be more expensive, but unless you have experience with these kinds of repairs, you may not have much of a choice.

Assuming you’re just talking about the cost of parts, again, this depends on what you’re trying to fix. Fuel lines are relatively cheap to replace, and even the most expensive ones shouldn’t run you more than $120.

Fuel injectors are more expensive and can cost between $150 and $600 depending on which ones you get, while fuel tanks are the most expensive part to replace and can cost upwards of $1,000 for a new one. 

How to Fix a Gas Leak in Your Car

While gas leaks are certainly a serious issue, many of them can, fortunately, be repaired without a ton of effort or money in many cases. Here’s how to repair some of the issues that might cause your fuel system to leak:

How to Fix a Bad Fuel Tank

If the damage to your fuel tank is really bad, you’ll probably just have to replace it outright. If the damage is less severe, however, you may be able to repair your tank with some purpose-built epoxy.

To repair your fuel tank:

  1. Jack your car up, and place it on jack stands so that you have access to the underside.
  2. Inspect the gas tank and find the source of the leak, if you haven’t already done so.
  3. Take a piece of sandpaper and sand the area over and around the leak. 
  4. Using a rag soaked in alcohol or a degreaser, thoroughly clean the area you just sanded. Sanding and cleaning the tank will help the epoxy adhere to the tank much more strongly.
  5. Mix the epoxy according to the manufacturer’s instructions.
  6. If you’re repairing a crack, apply the epoxy over the surface of the crack, making sure to press it in.
  7. If you’re repairing a small hole, instead take a small piece of the epoxy and shape it into a cone that will fit into the hole.
  8. Press the epoxy cone into the hole in the fuel tank, and smooth over the remaining epoxy on top of it. 
  9. Wait for the epoxy to dry, and then fill up your tank with some gas to test your repairs.

How to Fix Bad Fuel Lines

If your fuel lines have actually broken, there’s no way to fix them as such; you will have to replace your old fuel lines with new ones.

Of course, there’s a chance that your fuel lines were simply installed incorrectly, in which case you just need to make sure that your fuel lines are connected to their mounts in the right way.

In either case, here’s how to properly install fuel lines:

  1. Jack up your car and secure it in place with jack stands.
  2. Get under your car and look for the fuel lines. If you find the fuel filter, the fuel lines will be connected to it.
  3. You’ll need to relieve the pressure in your fuel system, or gas will spray everywhere when you remove the fuel lines. To do so, start your car, then locate the fuse in your fuse box that is connected to the fuel pump and pull it. The car will shut off and the pressure in the fuel system will have dissipated.
  4. Place a catch can under the fuel filter, and loosen the hose clamps that secure the fuel lines to the filter. Once this is done, remove the fuel lines from their other mounting point.
  5. Attach the new fuel line to both of its mounting points. Once you’ve confirmed that the fuel lines are the right length and aren’t kinked up, use hose clamps to secure each end of the fuel line to its mounting point.

How to Fix Bad Fuel Injectors

Once again, if your fuel injectors are broken, replacing them is the only way to actually fix them. Here’s how to do so:

  1. Make sure the engine is cold and the battery is disconnected before you begin.
  2. Disconnect the bolts and brackets that keep the fuel rail secured. You may also need to remove the fuel line from the fuel rail in order to remove it from the intake manifold.
  3. Remove the plastic engine cover.
  4. Disconnect the electrical connector for each injector.
  5. Lift the fuel fail off of the intake manifold. The injectors will be lifted along with it. Take care not to bend the fuel rail during this step.
  6. The fuel injectors may be held in the fuel rail with clips. Remove these clips, and then pull the injectors from the fuel rail. Watch out, as they’ll probably drip some gas when you do this.
  7. Wet the tips of your new injectors with a bit of engine oil before putting them into the fuel rail. This will make the seal between the two parts more effective.
  8. Press the new injectors fully into the fuel rail, and reinstall the clips if required. 
  9. Reattach the fuel rail, making sure the injectors are properly seated in their holes.
  10. Plug the electrical connectors into the injectors, and reattach the fuel line if necessary.
  11. To test your repairs, turn the ignition to the “On” position, and give the fuel pump a few seconds to fill the fuel lines. Then, start your car and run it for a few minutes. Afterwards, turn your car off and check the injectors to see if they’re still leaking.

Can I Drive My Car If It Has a Gas Leak?

Can you drive your car if it’s leaking fuel? Technically yes. But should you drive your car if it has a fuel leak? Probably not.

Gas is flammable, and if your leak happens to be over a part of the car that gets hot, then you’ve got a pretty severe fire hazard waiting to happen. Even if the fuel leak is in the tank or another part of the car that isn’t subject to extreme heat, why take that chance?

If you notice that your car is leaking gas, you should either repair it yourself or take it to a repair shop as soon as possible. 

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