ATVs are prone to getting water in the fuel from rough off-road use or sitting without being used for extended periods.

Too much water mixed with the fuel may cause severe engine damage, so you must troubleshoot and resolve the problem.

Knowing what symptoms to look for can help identify an issue like this early on.

Common Symptoms of Water in the Gas

Your ATV needs clean, high-quality fuel of a grade specified by the manufacturer to run correctly. If water gets into the gas tank, it typically manifests as a sudden change in engine performance.

When water enters the combustion chamber, it turns into steam, and the spark plug cannot ignite. Also, the steam doesn’t compress like vaporized fuel, which interferes with engine compression.

The severity of the symptoms depends on how much water there is in the gas. Typically, the symptoms gradually worsen as the water content increases.

Difficulty Starting

Most engines can start with a minor amount of water in the fuel. However, if the water level becomes too high, it can disrupt the ignition process and potentially prevent the engine from starting.

In this scenario, the engine cranks and might occasionally show signs of wanting to fire up without succeeding.

Rough Idling

A healthy ATV should idle at a steady engine speed between 1100 and 1700 RPM. If the engine does not run appropriately at idle, like if it’s about to stall out, there might be water in the fuel.

Stalling

While you might be able to start the engine, water in the gas may cause the engine to stall out, especially when idling or at low speeds.

Intermittent Misfires (Sputtering)

A misfire happens when a lack of fuel, spark, or compressed air randomly prevents the spark plug from igniting the fuel.

When an engine misfires, it feels like it shuts off for a fraction of a second before it resumes normal operation, causing the engine to run rough. This behavior is often referred to as engine sputtering.

Engine misfires can happen for various reasons, one being water in the fuel. Misfires due to water in the gas are typically more noticeable at idle or during acceleration.

Engine Hesitation

When you apply more throttle, you expect the engine to speed and the ATV to accelerate immediately. But if the engine hesitates for a short second before it begins to speed up, as it’s coughing, it displays a behavior known as engine hesitation.

Engine hesitation can be caused by a weak fuel pump or fuel/air mixture that is too lean, but it can also happen when there is water in the fuel.

Power Surges

A power surge is a sudden and irregular fluctuation in engine power, often occurring intermittently and without a regular pattern.

This usually involves the engine sputtering or hesitating, followed by an unexpected and excessive increase in engine speed.

Like many of the symptoms on our list, power surges can be caused by a range of issues like fuel injector problems, sensor problems, or a fuel pump going bad. Or, it can be caused by water in the gas.

Engine power surges due to water in the fuel can happen out of the blue without any warning and with no apparent pattern.

Reduced Engine Power

If you’re noticing reduced engine performance from what you’re used to, water in the gas should be one of the first things on your list of possible causes.

Poor Fuel Economy

When water interferes with ignition, the engine no longer optimally burns fuel, negatively affecting your ATV’s fuel economy.

Check Engine Light

If your ATV displays a check engine light, having the fault code read can tell you there’s an issue with too much water in the fuel.

How to Know the Symptoms Are From Water in the Gas?

Many of the symptoms listed above are not exclusive to a water-in-the-gas scenario, making it harder to determine if they are caused by water-contaminated fuel or other things.

The first thing to do is to note whether the symptoms appeared suddenly or occurred gradually over time.

If the symptoms came shortly after you filled your tank, the gas you used likely contained water. In rare cases, even pump gas can be contaminated by water for different reasons.

If you’re experiencing one or more of these symptoms in your ATV, ensuring the gas is good might be a good start before working through other possible causes.

How Does Gas Get Contaminated by Water?

There is always a tiny amount of water in the gas from condensation, but what could be the cause when there is so much water that it’s starting to cause an issue?

Through the Gas Tank Vent Tube

The gas tank needs a way to let air into the tank as the fuel level drops. Otherwise, there would be a vacuum buildup inside the tank, and the gas pump would struggle to get more gas out.

Air is let into the tank through a vent in the gas cap or a separate vent tube. In extreme weather conditions with heavy rain, when washing with a pressure washer or submerging the ATV in mud or water, water may get into the tank through the air vent.

Through a Leaky Gas Cap

Gas caps usually do an excellent job of keeping water out of the tank, but if the seal is damaged or the lid is not on correctly, it may not seal.

Gas Containing Ethanol Going Bad

Most gasoline sold in the US has an ethanol content between 10% (E10) and as high as 85% (E85).

Ethanol likes to bond with water vapor in the air, causing the water content in the gas to increase as the gas breaks down.

From Condensation

Rapid temperature swings can, in theory, cause condensation to form inside the gas tank, but this is not common as the tank is part of a sealed system.

However, large storage tanks are more prone to condensation or leaks, and there’s always a chance the fuel was already contaminated when you bought it at the pump.

Can Water in the Gas Damage the ATV?

All petroleum contains a small amount of water. For E10 gas, the water content by volume is typically up to 0,5%.

Minute amounts of water in the fuel like this won’t cause any of the above symptoms or damage the ATV.

However, if the water content gets too high, it has the potential to cause severe engine damage.

In carbureted ATVs, water in the fuel may cause corrosion inside steel gas tanks, leading to carburetor issues. Replacing the tank and rebuilding the carburetor typically solves the problem.

In fuel-injected ATVs, the damage potential is more significant.

Water entering the fuel injectors expands rapidly as it passes through the injector tips due to the high temperature. The expanding water can deform the injector, potentially leading to a costly fuel injector replacement.

What To Do if Your ATV Gets Water in the Gas?

When you suspect having water in the fuel, you want to remove it and not continue burning it to ensure it doesn’t cause any damage.

The safest and best alternative would be to drain the fuel tank and flush the fuel lines to replace the contaminated fuel with fresh new fuel.

Water is denser than gasoline and always drops to the bottom of the tank. If your tank has a drain plug, you might be able to drain out most of the water while leaving the gas in the tank.

However, if your ATV has only a tiny amount of water in the fuel, you can remove the water by using a water remover additive. These additives contain methanol or isopropyl alcohol that mixes with the water and turns it into a combustible substance.

Products like ISO HEET, designed to remove water, are said to be up to five times more effective in eliminating water from the system than standard antifreeze.

Another alternative is filling the tank with premium fuel to dilute the water content as much as possible.

How to Prevent Water From Getting Into the Gas Tank

The best alternative is preventing water from getting into your ATV’s gas tank in the first place. Here are a few simple steps that will drastically reduce the chance of getting your fuel contaminated by water.

Buy your gas from a busy gas station with a high fuel turnover rate where the gas is always as fresh as possible.
Ensure the gas cap seal is undamaged and that the gas cap is on tight.
Never direct the nozzle of a pressure washer towards the gas cap or vent-tube area.
Never drive in waters deeper than the gas cap, even if your ATV has a snorkel kit installed.
Fill up the tank and add a fuel stabilizer before long-term storage.
Store the ATV indoors to keep it out of the worst weather.

The Bottom Line

Getting water in your ATV’s gas tank can be annoying, but it isn’t the end of the world. If you resolve the issue before running for too long, it will likely not cause any long-term damage to your ATV.

9 Symptoms of Water in Your ATV’s Gas & How to Fix It