7 Reasons Why Your Car Smells Like Gas and What to Do About It?

It’s both annoying and worrying when you start asking in the middle of driving, “Why do I smell gas when I start my car?” So you’ll park in a bay and keep on sniffing anywhere in your car.

You cannot mistake that there’s a gas leak when you smell gas in car. Whether you are outside or inside your car, gas leaks in the car are one of the fluid leaks that you can easily recognize. Aside from the annoying gas smell in car, it leaves a breathing discomfort while on a parking lot or driving.  

Here we list common 7 reasons casused it and how to do.


Gasoline is a secondary fuel. It powers up a car’s combustion engine. Coming from crude oil, it composes different hydrocarbons mixed in the air. In 2018, the transportation sector used 69% of fuel in the United States.

Gas leaks are both dangerous to people and your car.

Why You Should Not Ignore a Car Leaking Gas?

It becomes troublesome when you wonder why the car smells like gas when I start but it goes away. And suddenly, the car smells like gas when parked. Never ignore the recurrences of gas leaks!

1. Gas leaks are flammable.

Gas leaks come from vapors of fuel. When fuel vapors mix with the air, these have a high potential of igniting the fire with a little spark. Gasoline stations have warning signs not to use cell phones or light cigarettes when topping up

2. Gasoline fumes in car are toxic.

Topping up with gasoline cannot be harmful unless inhaled in large amounts. It can result in gas poisoning. Never pump your vehicle too much in a closed area such as the garage. One may have difficulty in breathing, vision loss, headache, or loss of consciousness.

Too much exposure can lead to lung damage.

3. Gasoline leak means further repairs in the fuel system

There’s potential damage to your fuel system when your car smells like gas and has trouble starting. When the vehicle is incredibly low on fuel and started jerking, it means that there’s a problem with fuel delivery.

Causes of Gas Leaks

Missing, Loose, or Damaged Gasoline Caps

Missing Gasoline Cap

Car owners often mistake fuel leaks in the car for a missing cap after a repair or top-up. It pays to check the gas lid first before freaking out.

The cap secures the fuel vessel to prevent fuel from spilling. Rubber seals a cap. When the gas tank is not covered, vapor mixes into the air. It becomes one reason why the car smells like gas but no leaks.

What to Do? - Do not drive along with the uncovered gas tank. Buy a replacement cap.

Loose Gasoline Cap

Car owners or pump attendants often overlook tightening the cap after top-ups. Possible occurrences of a loose cap happen when filling gas during rush hours.

What to Do? - Regularly check the gas lid.

Faulty Gasoline Cap

Another possible reason is loose or lost rubber seal. In turn, the cap may flop out of the tank without any reason, decreasing engine performance. Faulty gas cap leads to gas smell, decreased mileage, and check engine light signage. 

What to Do? - A faulty cap needs replacement. Next time you notice that your car smells like gas after filling up, check your gasoline cap.

Reason 2. A Hole or Damage in Fuel Tank

External forces under the car chassis may bring damage to fuel tanks. Accidents, corrosion, rust, and leaks may damage your fuel tank. Filling up your tank with the wrong fuel can damage your fuel tank system.

Punctures and dents can lead to fuel leaks. Strong gasoline smell in the car means an excessive fuel loss in your tank.

The materials used for car fuel tanks can be steel, aluminum, or plastic High-Density Polyethylene. Holes in fuel tanks can be hard to find.

While manufacturers designed car fuel tanks to withstand heavy road bumps, it doesn’t excuse a tank from damages.

What to Do? - Bring your car to a mechanic. Mechanics have great eyes for spotting damages to your fuel tank. You can seal the tank with epoxy, weld the tank, or replace the tank if needed.

How to Seal the Car Fuel Tank with Epoxy?

Prepare the following:

  • Gas tank repair epoxy
  • Carjack
  • Jack stand
  • Safety shoes and glasses
  • Filtration mask
  • Sandpaper
  • Degreaser

Wear your safety gear. Jack up the car using a car jack and rest it with a jack stand. Space should be safe enough for you to find the hole and make the necessary fixes. Go under the vehicle, find the leak, and sand it.

Clean the hole or leaking area with a degreasing agent. Make sure it is clean and dry enough for the epoxy to hold on to the surface. Mix the epoxy and use it before it becomes dry.

Shape the epoxy into a cone and fill the hole. Insert it as much as it can go. Smooth the remaining epoxy. Wait for the epoxy to cure and dry. Test for further leaks before filling out with gas.

How to Weld Car Fuel Tanks?

Warning: Only professional welders should perform this job!

Remove all sources of ignition. Remove the battery before draining. Drain fuel using only approved siphoning equipment. Drain on well-ventilated places away from the inspection area. Ensure that the tank is clean and tested free from any flammable vapors or fumes. Another security measure before welding is to fill the tank with water along the welding area.

Wear protective gears before welding. Carefully weld directly on the arc at the center of the puddle without weaving or whipping to avoid burn-through and warping. Use a backing bar to dissipate the heat. Test the tank and make sure there is no gasoline smell in the car.

Reason 3. Holes or Cracks in the Fuel Lines

Fuel lines or hoses connect the engine and the fuel tank. Fuel distributes fuel to the engine.  The lines are prone to cracks and leaks because it sits under the car. Designed thick enough to hold the fuel pressure, a sudden drop of pressure indicates an efficiency failure. 

What to Do? - Replace broken fuel lines with new hoses.

How to Replace Broken Fuel Lines?

Using protective eye gear, jack up your car and place a jack stand to hold your car’s weight. Place drip pans under each connection to find out which line has leaks. Use open-end wrenches to loosen the fuel lines. Turn it counterclockwise. Use a flat crew driver to loosen mounting clamps. Fit into new lines clockwise to replace the broken lines.  Do not over tighten the lines.

Reason 4. Exhaust Fumes from Unburnt Gases

When a car smells like gas when AC is on, you have an exhaust leak. Unburnt vapor causes gasoline smell inside the car. When gas fumes leak, it goes through the passenger compartment.

Identify the exhaust leak when you accelerate your engine. A loud ticking noise near your engine, noisy acceleration, bad fuel efficiency, and bad odor is also an indication of exhaust leaks.

What to Do? - An exhaust leak could be small or big. To find the exhaust leak, use a car jack and a jack stand to lift your car. Go beneath your car and look for the leak. Clean the area affected with sandpaper to remove dirt and rust. Seal it with tape or epoxy.  Fix a leak of more than three inches with an aluminum patch or bring it to your mechanic.

Reason 5. Loose or Broken Spark Plugs

When your car smells like gas when idling, there’s a leak anywhere on your car mechanism. Although fuel doesn’t flow on spark plugs, a broken piece of it will not seal using the right torque. The crush washer or unsealed ring will leak fumes. If your car AC smells like gas, it means the vapors went through your car’s HVAC system. A gas smell when starting a car could be loose or broken spark plugs.

What to Do? - Check the condition of your spark plugs one by one. If there are no broken wires, it indicates that the crush or sealing washers are loose. If it’s broken, you have to replace spark plugs.

Reason 6. Fuel Injector Leaks

Fuel injectors serve as nozzles that release fuel to the fuel system. An O-ring or rubber seal serves as a sealer in fuel injectors that prevents the combustion chamber from releasing gas fumes. A broken or worn off O-ring or rubber seal will release fumes from the fuel injector.

What to Do? - Replace the O-ring when the injector is not faulty. It’s as simple as putting on a rubber band to your hands or fingers.

Reason 7. Faulty Charcoal Canister

A charcoal canister absorbs and stores the vapor from the fuel tank. Fuel floods the canister when spilled. It reduces its emission control efficiency. Spilled fuel comes from in faulty pump nozzles. Watch out on your next top-up!

What to Do? - When a gasoline smell from car becomes unbearable, go to your service advisor to replace your charcoal canister.


Gasoline - energy education

crude and petroleum products explained - US energy information administration

Causes of gasoline poisoning - health line

Gasoline Fumes Harmful - science reference

Fix a Car That Doesn't Start - wikihow

Bad or Failing Gas Cap - your mechanic

Fuel tank - wikipedia

Repair a Leaking Gas Tank - cars direct

Charcoal canister- toyota nation

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