The last thing every driver wants is a car leaking gas when running. This issue not only means spending more on gas but can also cause poor performance and severe damage to the car. If you encounter this problem, pull over and locate the source of the leak.
In most cases, a damaged gas cap, excessive shaking, or a damaged gas tank will cause gas to leak when driving. Identifying the cause of a fuel leak can help you determine the best way to resolve this problem.
I explain why your car leaks gas only when running. I’ll also provide practical solutions so you can continue driving stress-free.
Answer: Reasons Your Car Leaks Gas When Running
The most common reasons for a car leaking gas when running are:
- Loose gas cap
- Damaged gas tank
- Excessive shaking
- Faulty gas lines
- Leaking gas injectors
Loose or Damaged Gas Cap
The gas cap covers/seals the opening of your car’s fuel tank. Doing so prevents gas from spilling out when driving, particularly on bumpy roads.
Gas in the tank creates high vapor pressure due to the enclosed nature of the tank. If the gas cap is loose, the high vapor pressure might escape. When this happens, your car will smell like gas when driving.
The gas cap can fail to close properly if its gasket is missing or brittle. This issue is common in old cars. Besides, an accident or excessive wear can cause the cap to bend or get damaged, leading to gas spillage. Thankfully, issues with the gas cap are easy to spot.
Remove the gas cap and ensure no debris prevents it from closing correctly. Tighten the cap if necessary. If the gas cap looks worn, bent, or broken, replace it.
Damaged Gas Tank
A gas tank will last for a decade without developing leaking problems. However, exposure to elements can cause the tank’s walls to become thin and brittle. With time, your gas tank might develop thin cracks or tiny holes.
Furthermore, physical damage from an accident can damage the tank. If the cracks or holes are on the upper section of the tank, gas might leak when driving. In this case, gas will shake in the tank and reach these holes or cracks. You’ll also experience a leakage problem if you overfill the fuel tank.
Replacing a leaking gas tank is the only solution to this problem. Keep in mind that gas tank replacement can cost you up to $1,500, depending on the car model and the tank you choose.
Excessive Shaking
If your car leaks gas only when running, the cause could be excessive shaking. This issue happens when you drive on rough or rocky terrain. The shaking or vibration destabilizes gas in the fuel system, making it leak from various parts.
Gas in the tank might hit and open a loose gas cap if riding over a rocky road. As a result, your gas will start to spill out as you continue driving.
Driving on such a road can trigger premature wear of parts in the fuel system. Usually, rocks and other debris will knock fuel line connections and other components, making them loose or worn. As the fuel shakes, it might hit these parts and leak.
Ensure the gas cap is tight before driving on rough or rocky terrain. If the leak comes from worn or loose parts in the fuel system, allow a professional to inspect and replace them.
To reduce shaking while driving on rocky terrain, improve your shock absorbers and ensure your tires are in good shape. You can also consider wheel balancing and alignment to reduce vibrations.
Faulty Gas Lines and Hoses
The gas intake system has several lines and hoses that channel gas into the combustion chamber. These lines and hoses must be in tip-top condition to supply the engine with sufficient gas. But like other car components, gas lines and hoses can wear out and start to leak gas.
Debris and contaminants in metal gas lines can cause corrosion and premature wear. While this is rare, the worn fuel lines might start to leak fuel when you drive.
High temperatures can melt your hoses, leading to gas leakage. The pressurized gas will hit the worn, cracked, or damaged parts and leak. If you suspect the gas lines and hoses are to blame, allow an experienced mechanic to repair or replace them.
Leaking Gas Injectors
Gas injectors introduce/inject pressurized gas into the internal combustion engine. They spray fuel in the engine when you start the engine and as you continue driving. When the injectors are in good shape, they will ensure your engine has the proper fuel mixture for complete combustion.
So, how can gas injectors leak fuel when driving? Gas injectors have O-ring seals at the base. These parts provide vacuum pressure to help the injectors work properly. If they’re in good condition, they act as a seal, preventing gas vapors from leaking or air from leaking into the injectors.
Unfortunately, the O-rings can become brittle or cracked and fail to seal the injectors. They usually fail due to age, wear, and exposure to chemicals or high temperatures. Damaged O-ring seals will cause gas to leak when driving.
In this case, you should remove the injectors and pull out the O-ring seals. Replace the old O-ring seals if they look worn or damaged.
Before installing your injectors, soak them in an injector cleaner to remove accumulated deposits. You can also use an injector bore cleaning brush to remove stubborn gunk.
Symptoms of Car Leaking Gas Only When Running
You might notice the following symptoms if your car leaks gas only when running:
- Car smelling like gasoline: If your car is leaking gas when driving, the first sign you might notice is a distinct smell of gasoline. The smell is prevalent when operating at full throttle, especially when driving uphill or accelerating.
- Drop in gas levels: A car leaking gas when driving will cause an abnormal drop in fuel levels. You can tell there’s an issue with the gas depending on how the gas gauge drops.
- Engine misfiring: Gas leakage and a significant drop in gas level can lead to various engine performance issues. The cylinders will sputter and misfire. If you continue driving, the engine will gradually lose power and stall.
Question: Is It Safe to Drive a Car With a Gas Leak?
While you can continue driving the car, a gas leak can be a safety hazard. Gasoline is flammable. It can leak on a heat source, ignite, and cause a fire.
Gas fumes are toxic, thanks to benzene and other harmful chemicals. Inhaling vapors from leaking gasoline can cause nausea, headache, dizziness, and confusion. Exposure to extremely high levels of gas vapors can cause fainting.
Wrapping Up
You now know what to look for if your car leaks gas only when running. The first thing you should do is find a safe spot to pull over. Then, inspect the fuel system to identify the source of the leak.
Usually, a damaged gas tank, loose gas cap, excessive shaking, worn injector O-rings, and damaged gas hoses are to blame. If you’re not a DIY enthusiast, contact a reputable towing company or an authorized mechanic to get the leaking part fixed.