Water in the fuel tank of your vehicle is a huge problem and should be addressed immediately. Water may enter your gas tank while filling it at the pumping station. It may even condense into your tank due to the weather. Water may collect in the fuel tanks of older vehicles with rusty fuel tanks. This may also happen in a tank with bad tank breathing conditions.

Tank breathing occurs when the fuel is held in the tank. The concentration of the gasoline vapors in the space above the liquid level may vary according to the temperature and pressure of the area the tank is in and the operating conditions.

If it gets too hot, the liquid fuel evaporates into the vapor state. If it is too cold the fuel vapors condense back into the liquid. But water condensation along the inner and outer surface of the fuel tank may occur. This condensed water may mix in the fuel held in the tank – leading to fuel contamination.

When you turn on the ignition the fuel flows into the combustion chamber and the spark plug ignites the mixture of fuel and oxygen. This mixture creates an explosion that cranks the crankshaft to rev your engine and move the car.

But what will happen if water enters the combustion chamber instead of the regular or correct mixture? There will be no ignition or a weak explosion when the spark plug tries to ignite the mix.

Symptoms of Water Contaminating the Fuel

Here are the symptoms that indicate there is water in your fuel tank.

Rough acceleration – occurs when the water tricks the air and fuel sensors. The Mass Air Flow (MAF) sensors pick the air and fuel mixture entering the combustion engine. The air mass is important as the engine control unit delivers the right amount of fuel to the engine. In this case, the fuel is mixed with water. It tricking the engine into running water instead of gas. This causes the engine to splutter due to incorrect mixture leading to a rough acceleration. This is the most common sign of water in the gas tank.Symptoms of Water in Gas Tank and How to Fix It in 2020

Fuel Injection Failure – Nowadays petrol or MPFI engines have injectors that supply fuel to the combustion chamber instead of the carburetor. The pore size of the injectors is designed to spray just the right amount of fuel in all conditions. The injector’s efficiency depends on the right density of the fuel. Water is denser than petrol thus cannot be sprayed as easily as the oil. This produces stress in the injector leading to its failure. In diesel engines, the fuel filters can remove foreign elements to a certain extent. But high amounts of water in the fuel can cause problems as fuel injectors in diesel engines work at higher spray pressure.

Engine misfires – This occurs when the water enters the combustion chamber of the carburetor’s cylinders. This misfiring occurs due to the same reason – water mixing with the fuel.

Rough idle – is when you feel the car run bouncy and rough when you turn the ignition. This may damage the engine and maybe cause due to clogged filters and water in the fuel. When a faulty air-fuel mixture enters the idle engine, it is susceptible to mistakes and damage. Most symptoms associated with water in the gas tank become evident when the engine is idle.

Check the Engine Light – Most modern cars have a built-in monitoring system for the sensors in the engine. If a sensor reads faulty values, it sends information to the engine control unit. Sometimes it stores the trouble code in its memory; at other times it lights up to indicate a serious problem.

Steam in the Exhaust – Weather there is water in the exhaust pipe or in the combustion chamber it will evaporate on heating and you will see steam. If you notice more steam emitted from your car’s exhaust than usual. This is a sign there is water in your fuel tank.

Slow Acceleration – All the sensors fitted in the car ensure that a correct mixture of air and fuel go into the carburetor. If the mixture is faulty the reading will differ to indicate the engine is run too lean or too rich. This affects the power of the engine. When power reduces, the acceleration will be slow.

Lubrication Issues – If the gasket in the engine is faulty, the water may get into the engine and leak into the oil sump. If large amounts of water get in then it forms a sluggish mixture with the engine oil that affects the lubrication in the engine.

Difficult Starting Condition – The moment of the startup of the engine is critical. If the fuel-air mixture is not Symptoms of Water in Gas Tank and How to Fix It in 2020perfect the spark plug will not ignite it to rev up the motor engine. If the mix does not have sufficient fuel – the spark plug will not ignite the fuel. If there is too much fuel the spark may be doused or drowned. If you have water in the fuel tank – most probably the latter may be the case. If you have longer crank-up times for your engine – it is an indication – there is water in your tank.

Hydro-locked engine – When you have too much water in the fuel tank the engine will not start up or crank up at all. This condition is called hydro-locking. This happens because water cannot be compressed like air. Normally the pistons compress air in the pistons and push the fuel into the carburetor. But water does not behave like oil as the compression ratio is different. This will cause the engine to seize and lock up. The friction will also damage the internal parts such as the crankshaft rods. Though it is not common; but for this eventuality to occur the fuel should have a lot of water in it. If this does happen then unscrew the spark plug to ensure that the crankshaft engages.

Vehicle stationary for a while – Usually when the car moves the fuel and water mix and churn due to the motion of the car and the suction of the fuel pump. But when the vehicle has been immobile for a while the water and oil separate. The oil floats on water. Most fuel pumps pull in fuel from the bottom of the tank. This means that when you rev up a car that has been stationary for a while the pump will pull up water into the engine.

How Does the Water Get into The Tank?

Now you know the symptoms of water mixed in your fuel. You would like to prevent it thus would like to know – how does water get into the tank?

There may be many reasons;

The fuel tanks cap may be loose – The caps have a gasket at the mouth that forms an airtight seal for the fuel tank. If the gasket is loose, if the seal is incorrect then the running water from the rain can enter the fuel tank. The water can even condense on the inside as the difference in the pressure inside and outside the tank may pull in the humid air. The humid air when cooled further during the night or in cooler weather may cause water to condense out of this trapped air and drip along the tank’s sides into the fuel. To prevent this eventuality, ensure the cap is closed tightly and the tank is sealed correctly.

The tank may have a leak near the top – Older vehicles had steel tanks that could develop rust holes near the top of the fuel tank. First of all, rust is porous and allows water to soak through. And if the holes are not treated the water will flow into the tank while it is raining, at the car wash or other similar conditions. As there is no airtight seal on the fuel tank humid air can get into the tank via these leaky and rusted spots. If you have an old car – correct this condition with waterproofing and replacing the gasket to make the tank airtight and leakproof. Newer vehicles have plastic tanks whereSymptoms of Water in Gas Tank and How to Fix It in 2020 these conditions are unlikely to occur.

Bad tank breathing or EVAP – If your Evaporative Control System (EVAP) is not working correctly or there is a leak in your tank, condensation can enter the gas tank.

Check the control valves of the EVAP system – there should not be any leaks and they should be in good condition. The best way to check this system is to get an EVAP Smoke machine. If you are not sure where to get one and what to check – call a mechanic.

If your vehicle has been standing for a long time and has not been refilled during this time. It may gather water due to condensation.

Sabotage – Now you have checked the cap of the gas tank and the vehicle’s EVAP system. You found that both are in good condition but you don’t know where the water in the fuel tank came from? Then the only likely answer maybe – someone deliberately put water in the tank to harm you.

Water in The Gas Tank – How to Fix It?

Now you know the causes of water getting into the fuel tank. You may be looking for solutions on how to get this water out and dry the tank from inside. So as to prevent the engine seize-ups and other damage to your wheels.

Empty the tank – The best thing to do would be to empty the tank and let it dry completely. Then refill it with clean uncontaminated fuel. This can be time-consuming and may require some equipment such as a siphoning pump etc. Remember this that the fuel pump of your car is fitted a few millimeters above the bottom of the tank and some water may be left behind. Ensure you have removed all of it by allowing it to evaporate. To ascertain this job has been done well – take your care to its doctor – the mechanic.

Fuel Storage Gas Caddy – These are portable cans that have a two-way rotary pump. It can fill and siphon off fuel by reversing the crank. You can put the hose to the bottom of the tank to siphon off all the water and fuel from the tank.

Replace the fuel filters – to prevent the water from entering the engine. Replacing the fuel filters is imperative as water-soaked filters affect the efficiency of fuel filtration.

Fuel additives – There are some fuel additives that emulsify water by bonding to them and encapsulating them. This removal or binding of water turns the non-combustible contaminated fuel into a combustible organic compound. As the engine runs the water is burnt along with the gas and released as steam. This steam helps clean your engine.

Putting this additive will prevent the blockage of fuel lines and filters. It will prevent damage to the injector tips, prevent acid formation, and corrosion. It will also prevent microbial growth in the fuel tank. These additives also stabilize old fuel, reduce emissions, lubricate the system, eliminate water, and clean the automobile system.

Methanol-based additives and petroleum distillates can be used to cut out the effect of water contaminated fuel. But they work only when very small amounts of water contaminate the fuel.

Rubbing alcohol – sinks to the bottom of the gas tank and absorbs or mixes with the water. This mixture eventually enters the engine and burns with the fuel. However, it is recommended that this procedure should be done only by highly experienced and skilled mechanics.


In conclusion, water in your car tank can dramatically affect your car’s performance and lead to costly repairs. Symptoms of Water in Gas Tank and How to Fix It in 2020Replacing your corroded fuel pump damaged by water can be quite costly. There are many ways water can get into the gas tank such as rainy weather. If you do not shut the fuel cap properly – water can flow or drip into the tank. A bad water filter from the fuel station can cause water to get into your tank along with the gas.

There are many indicators of water contaminating your fuel. The first being your engine not starting or staying on. Water prevents fuel from combusting. Your car may hesitate or not accelerate properly. This because the engine is not getting the correct fuel mix. This may also cause the engine to rev, sputter, or jolt upon acceleration.

It is very important to remove the water from the gas tank as it can damage the fuel injectors or cause rust all over the fuel system over time. Do not empty the fuel tank by driving the car to empty. As water can cause more damage to the engine this way.

Instead, try these recommended methods. The first one being – remove all the contaminated gas and replace it with higher octane fuel. This displaces the deluded gas from before. You can drain the tank by unplugging the tank under most vehicles or siphon off the fuel.

You can even leave the cap open to allow the vapors to evaporate out of the tank. You can even add some additives if there is only a small amount of water contaminating the fuel. It is always recommended that you consult the experts as you may end up hurting yourself or harming the car and the environment.