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Home / Symptoms / Car Leaking Gas

Four common causes for a vehicle Leaking Gas and their related parts.

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Is Your Car Leaking Gas?

The gas leak is commonly caused by a crack or looseness in the fuel tank. However, it can also be caused by a misplaced gas cap, faulty fuel injectors, damaged fuel lines, valve leaks, or even a broken sensor allowing fuel leaks.

Gas powers our vehicles because of its flammability. So, when it leaks, it reasonably causes concerns. But, in addition to the fire hazard, gas vapors are toxic and harmful to the environment.

A vehicle's "check engine light" may indicate a fuel leak, and the "gas cap light" ensures your fuel system is sealed. Remember, this pressurized, sealed part is designed to safely contain fuel and harmful vapors.

Watch out: Gas leaks are easy to detect since they strongly smell and leave puddles under your vehicle. But, sadly, gas leaks don't only put the driver in danger but everyone around the car as well.

Let's Get To The Bottom Of It!

Do you have gas leaking under your vehicle wherever you park?

You might also smell gas fumes while driving or notice decreased fuel economy.

Fuel tanks are designed to reduce pollution by sealing fuel and vapors inside. But unfortunately, many modern vehicles have flexible plastic tanks that can weather, developing cracks in the seams. If this happens, a fuel puddle can build up under the car wherever it's parked.

Do you see a puddle of gasoline under your car when idling?

You may also smell gas fumes while parked or see a puddle of clear fluid under your car that changes colors on the surface.

The fuel line on a modern vehicle is a rigid, high-pressure plastic with quick-disconnect fittings that are formed on both ends. It's designed to carry the fuel from the gas tank to the injector rail. If the plastic line develops a crack or the rubber seals in the quick disconnects degrade, the line will start leaking as the fuel pump runs. Since the pump is idle, you'll notice gasoline puddling underneath the vehicle.

Do you smell gas when you are driving down the road?

You might also notice that the engine is difficult to start or the motor oil seems thin.

The fuel injectors are triggered electronically to open and spray atomized fuel into the intake. Some O-rings seal the injector to the intake and the fuel rail. These O-rings are rubber and can become brittle and crack over time. These seals start to leak during engine operation. Air pushed through the vehicle by the engine makes the gas smell more noticeable while driving.

Is your "gas cap light" on?

You may smell gas when opening the hood or have trouble starting the engine after fueling up.

The gas cap is sealed to the filter neck with an O-ring to prevent the escape of harmful vapors. However, these seals are rubber, which can rigidify and crack over time. When these cracks develop, the evaporative emission system cannot form a vacuum to hold pressure in the fuel system. This failure turns the gas cap light on.

Is your "check engine light" on?

You might also see a puddle of gasoline under the vehicle or smell gas fumes while driving.

The fuel pressure sensor on top of the fuel pump module detects pressure in the fuel tank to verify that no fuel vapor leaks into the atmosphere. If you lose pressure because of a seal leak, the "check engine light" will come on.

Is your vehicle hard to start after filling up with gas?

The engine might also be hard to start at other times, and you might smell gas when opening the hood.

The purge control valve is designed to stay closed, only occasionally opening to evacuate gas fumes accumulated in the charcoal canister. This helps to dry out the canister. However, if this valve fails and sticks open, adding fuel to the tank forces gas fumes into the intake, flooding the engine. You will experience this issue by struggling to start your car after getting gas.

The most common causes for a vehicle leaking gas

The most common causes for the car’s gas leaking:

Fuel tank leaking: The fuel tank stores your vehicle's fuel. Inside the tank, the fuel sits in the form of liquid and vapors. if the fuel tank cracks or becomes faulty, fuel vapor and liquid might leak out.
Fuel line leaking: Fuel lines are tubes that deliver fuel, transporting it to the places it needs to go. These fuel lines are constantly pushing fuel through, relying on seals and connections to avoid anything from leaking out. However, these lines can get damaged and lose sealing, resulting in gas leaks.
Fuel injector leaking: The fuel injector is essential for the vehicle's combustion system, spraying the right amounts of fuel inside the engine's chamber to provide proper power. However, if these injectors get damaged, they might start leaking fuel outside and inside the engine box.
Gas cap leaking: The gas cap is the plug that closes the gas tank. So, when you need to fill up fuel at the gas station, you need to remove the gas cap to put the nozzle in the tank's entrance. However, if the gas tank is faulty, it might allow vapor to leak out, resulting in a gas leak.
Fuel pressure sensor leaking: The fuel pressure sensor measures how high the pressure pushing fuel inside the vehicle's fuel system. The temperature sensor then sends the information to the engine control module, so it combusts with better performance. However, if the sensor is faulty and sends the wrong info, it might cause fuel overflow, resulting in gas leaks.
Purge control valve leaking: The purge valve controls how much fuel vapor goes from the charcoal canister, where they are temporarily stored, into the engine so it can be burned during combustion. However, if the purge control valve fails, it'll start sending more vapor than needed, resulting in gas leaks.

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Frequently Asked Questions

Do you have gas leaking under your vehicle wherever you park?

You might also smell gas fumes while driving or notice decreased fuel economy.

Fuel tanks are designed to reduce pollution by sealing fuel and vapors inside. But unfortunately, many modern vehicles have flexible plastic tanks that can weather, developing cracks in the seams. If this happens, a fuel puddle can build up under the car wherever it's parked.
Do you see a puddle of gasoline under your car when idling?

You may also smell gas fumes while parked or see a puddle of clear fluid under your car that changes colors on the surface.

The fuel line on a modern vehicle is a rigid, high-pressure plastic with quick-disconnect fittings that are formed on both ends. It's designed to carry the fuel from the gas tank to the injector rail. If the plastic line develops a crack or the rubber seals in the quick disconnects degrade, the line will start leaking as the fuel pump runs. Since the pump is idle, you'll notice gasoline puddling underneath the vehicle.
Do you smell gas when you are driving down the road?

You might also notice that the engine is difficult to start or the motor oil seems thin.

The fuel injectors are triggered electronically to open and spray atomized fuel into the intake. Some O-rings seal the injector to the intake and the fuel rail. These O-rings are rubber and can become brittle and crack over time. These seals start to leak during engine operation. Air pushed through the vehicle by the engine makes the gas smell more noticeable while driving.
Is your "gas cap light" on?

You may smell gas when opening the hood or have trouble starting the engine after fueling up.

The gas cap is sealed to the filter neck with an O-ring to prevent the escape of harmful vapors. However, these seals are rubber, which can rigidify and crack over time. When these cracks develop, the evaporative emission system cannot form a vacuum to hold pressure in the fuel system. This failure turns the gas cap light on.
Is your "check engine light" on?

You might also see a puddle of gasoline under the vehicle or smell gas fumes while driving.

The fuel pressure sensor on top of the fuel pump module detects pressure in the fuel tank to verify that no fuel vapor leaks into the atmosphere. If you lose pressure because of a seal leak, the "check engine light" will come on.
Is your vehicle hard to start after filling up with gas?

The engine might also be hard to start at other times, and you might smell gas when opening the hood.

The purge control valve is designed to stay closed, only occasionally opening to evacuate gas fumes accumulated in the charcoal canister. This helps to dry out the canister. However, if this valve fails and sticks open, adding fuel to the tank forces gas fumes into the intake, flooding the engine. You will experience this issue by struggling to start your car after getting gas.

Typical fixes to address the cause(s)

These are typical processes and repair services that fix a check engine light issue

The most common cause: Fuel tank leaking

The most common reason for a car leaking gas is due to a fuel tank leak. The fuel tank is a container that holds your vehicle's fuel. The fuel tank is commonly the cause of fuel leaks since it relies on many seals and a gas cap. If there's any crack in the tank, or even if the gas cap is loose, fuel vapor and liquid leak out.

Symptoms it causes: Apart from the fuel leaking you might notice bad fuel economy, engine sputtering, EVAP warning light on the dashboard, etc.
High risk of priority: A leaking fuel tank eventually leads to your vehicle losing fuel level. If your vehicle starts running low on fuel, most of its internal combustion won't operate, resulting in power loss, bad performance, and even a breakdown.

How exactly does the fuel tank leak?

The fuel tank is incredibly resilient and well-protected in most modern vehicles. However, since the tank relies on many seals, which are not as resilient in material, the tank can start leaking over time. What mostly damages these seals is rough driving, bumpy terrain, and fender benders.

Go safe: Ask for a mechanic to inspect your vehicle's fuel system to investigate if the fuel tank is leaking due to surrounding components and if there’s further damage to check out. Many shops do transparent vehicle inspections and lay out your options after investigating your vehicle’s conditions.

What’s a vehicle inspection? It’s “detective work” on your vehicle, checking its systems to see if anything prevents the car from working as expected. In this case, mechanics examine different parts of your vehicle to track if anything is causing the fuel tank to leak. They’ll also check the condition of components during their inspection, noting which are causing the problem and which got affected by it, recommending to replace them in order of priority.

Transparency example in a leaking oil pan service

A fuel system inspection is the most transparent process to understand why your vehicle’s fuel tank is leaking. This is because many components surrounding the fuel tank, fuel injectors, and fuel lines can have a say in the issue, indicating the real culprits that caused it all.

Let’s read an example of how this kind of inspection helps to service a leaking fuel tank.

A customer dropped off their vehicle after noticing a puddle of clear liquid underneath it in their garage. They also reported a powerful smell of gas. They checked the gas cap and ensured it was tight before bringing the car in.

The technician did not notice anything about the customer's concerns on the test drive.

During the vehicle health inspection, the technician lifted the vehicle and saw that its gas tank was wet and smelled like fuel; these elements could indicate a fuel leak. To further investigate the issue, the customer authorized the shop to perform additional tests to confirm a fuel leak suspicion.

The mechanic pressurized the fuel system with a smoke machine and dropped the gas tank low enough to check the top for leaks. They found the leak and verified that it was coming from the seam on the side. Unfortunately, the gas tank will need to be replaced.

Fuel tank leaking

In this case, the mechanic put the “Immediate Action” tag on the evaporator temperature sensor.

Similar Symptoms

Below are just a few examples of typical Symptoms and Fixes your car might be experiencing

Four common causes for a vehicle Leaking Oil and their related parts.

Is Your Car Leaking Gas?

Let's Get To The Bottom Of It!

The most common causes for a vehicle leaking gas

Find Professional Help

Frequently Asked Questions

Do you have gas leaking under your vehicle wherever you park?

Do you see a puddle of gasoline under your car when idling?

Do you smell gas when you are driving down the road?

Is your "gas cap light" on?

Is your "check engine light" on?

Is your vehicle hard to start after filling up with gas?

Typical fixes to address the cause(s)

The most common cause: Fuel tank leaking

How exactly does the fuel tank leak?

Transparency example in a leaking oil pan service

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Why Is My Evap System Leaking?

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Why Is There Pink Fluid Leaking From My Car?