Fuel Pressure Drop: Why Your Atv Loses Power When Accelerating

If your ATV is stalling when you accelerate, it could be due to a number of issues. The most common reason is a blockage caused by a restricted flow of gasoline or airflow in the engine, often due to a dirty carburetor or air filter. Other possible causes include a faulty fuel pump, a clogged fuel line or fuel filter, or a vacuum leak. A weak fuel pump can also cause a drop in fuel pressure under acceleration. It is important to regularly maintain and service your ATV to prevent these issues.

Faulty throttle control mechanism

A faulty throttle control mechanism is a critical issue that can cause your ATV to accelerate on its own, leading to a potential loss of control and accidents. Here are some detailed instructions on how to deal with this issue:

Signs and Causes:

The throttle control mechanism regulates your ATV's speed, and if it malfunctions or gets stuck in the open position, it can cause unintended acceleration. Look for any signs of wear, sticking, or damage. This could include a throttle cable that is damaged, frayed, or has kinks in it.

Solutions:

• Regularly inspect and maintain the throttle mechanism. Lubricate moving parts as needed and ensure the throttle returns to the closed position smoothly.
• If you notice any issues, consider having your ATV serviced by a professional.
• If you have experience and the necessary tools, you may be able to address minor throttle issues yourself. However, for more complex problems, it is advisable to seek help from a qualified ATV mechanic.
• Clean and lubricate the thumb throttle mechanism if it hasn't been cleaned in a while.
• Remove the throttle cable and spray lubricant inside, allowing it to soak.
• Check the carburetor end of the throttle cable and ensure it is functioning correctly.

By following these steps and staying vigilant about maintenance and repairs, you can help ensure the safe operation of your ATV and prevent issues with unintended acceleration due to a faulty throttle control mechanism.

Clogged air or fuel filter

A clogged air or fuel filter can cause a range of issues with your ATV and should be regularly checked and replaced when necessary.

Air Filter

Air filters ensure that the air entering your ATV's engine is free from macroscopic particles of dirt and dust, which can damage components and restrict airflow over time. A clogged air filter can prevent air from getting into the engine, causing a rich fuel setting. This can be identified by black smoke blowing out of the exhaust pipe. Eventually, the muck sticking to the filter can break off and enter the engine. This will require you to change the air filter, engine oil, and oil filter.

Air filters should be checked and cleaned regularly, especially if you are riding in dusty and muddy environments. If the problem persists after cleaning, it is recommended to replace the air filter.

Fuel Filter

Fuel filters can become clogged with dirt and fuel byproducts. Clogged fuel filters can prevent fuel from reaching the combustion chamber, causing an imbalanced air-fuel mixture. This can lead to backfiring and a reduction in engine power.

It is important to inspect and clean your fuel filter regularly, especially if your ATV is operated in a dirty environment. If you notice a drop in performance or constant stalling, you may need to replace the fuel filter.

Faulty spark plugs

A spark plug is essential to ignite the fuel/air mixture in the combustion chamber. When the spark plugs are fouled, the coating on the tip of the plug prevents the spark from being generated, which causes the engine to misfire and results in further fouling.

• Hard Starts and Flooding: If your ATV's engine is hard to start or floods, it could be due to fouled spark plugs. This is often accompanied by sputtering and misfiring, and you may experience poor gas mileage and power loss.
• Rough Idle: A fouled spark plug can cause your engine to sound rough and uneven while idling. You may also feel the vehicle vibrating.
• Lack of Acceleration: If your ATV has lost its get-up-and-go and struggles to accelerate, bad spark plugs could be the culprit. Fouled spark plugs don't spark effectively, causing the vehicle to perform sluggishly.
• Reduced Fuel Economy: A sudden decrease in fuel economy can be a sign of faulty spark plugs. When the spark plugs aren't functioning properly, your vehicle's gas mileage can suffer.
• Engine Misfiring: Engine misfiring or hesitation instead of running smoothly may be attributed to faulty spark plugs. Interruption in the combustion process, even momentarily, can cause the engine's performance to suffer.
• Inability to Start Engine: In some cases, fouled spark plugs can prevent the engine from starting altogether. If your ATV won't start, it's worth checking the spark plugs as a possible cause.

It's important to note that while some of these issues can be temporarily resolved by cleaning the spark plugs, others may require a full replacement. Additionally, underlying issues causing the spark plugs to foul should be addressed to prevent recurrence.

Dirty carburetor

A dirty carburetor can cause a host of problems with your ATV. The carburetor is the section of the engine where fuel is transformed into vapour and mixed with air to be ignited in the vehicle cylinders. If your engine is running roughly, or idling harshly, it probably means there's some dirt clogging the carburetor.

A dirty carburetor can be the reason your ATV is stalling when accelerating. The most common cause of an ATV engine stalling when accelerating is the blockage caused by the restricted flow of gasoline or airflow in the engine, which is often due to a dirty carburetor or air filter. This can happen when the ATV is used for some time without maintenance.

If your carburetor is badly clogged, you will need to disassemble and clean it. This is not a difficult task, and only requires basic mechanic skills and a specialised carburetor cleaner. You can also take off the float bowl without taking apart the entire carburetor. Clean the bowl with carburetor cleaner and a toothbrush, and also clean the main and slow jets. Before you reconnect the bowl, check the bowl gasket to ensure it isn't damaged.

Most problems with carburetors involve improper adjustment. There is an ideal mixture of fuel and air that your car engine needs to run at maximum efficiency. Problems with your carburetor and engine could be a result of this mixture being off. To find out if the mixture is optimum, find the point at which your engine revs at peak efficiency. If there is too much air, it slows down. If there is too little, it also slows down. Somewhere in the middle, it will run the fastest.

You can adjust the carburetor by turning a screw on its side. The farther the screw is screwed outwards, the more air is being allowed into the engine. With the engine off, turn the screw until it seats, and count how many turns this takes. Then turn the screw back to the baseline adjustment. Start the engine, and with the engine running, turn the screw in, or clockwise. Make 1/4 turns until you notice the engine speed drop. Then turn it counterclockwise until the speed goes back up. Work for a while until you feel you've found the "sweet spot".

If your ATV has been sitting for long periods or uses ethanol-based fuels, it will eventually have problems with the carburetor. It's a good idea to use high-quality gas and ride regularly or use a treatment like Stabil when leaving fuel in the tank long-term. Nevertheless, a carburetor will eventually require cleaning, so it's recommended to take it apart once a year if you can't use non-ethanol fuel or every few years if pumping race gas and riding regularly.

Faulty fuel pump

A faulty fuel pump can cause a range of issues with your ATV and is a common reason for performance problems. Fuel pumps are critical as they ensure the flow of gas through your ATV. There are two types of ATV fuel pumps: mechanical and electric. Mechanical fuel pumps are more common in older ATVs and rely on a vacuum created by the engine to suck fuel through a diaphragm, while electric fuel pumps are usually found in newer, fuel-injected ATVs and are located inside the gas tank.

• The ATV starts and then dies
• The engine idles but won't rev or take rev
• Reduced top-end performance
• Extended crank or hard starting
• Poor performance, such as engine sputtering or power loss during acceleration
• Unexpected stalling, especially during heavy loads or when navigating inclines

If you suspect a faulty fuel pump, there are several tests you can perform to diagnose the issue. One simple test is to listen for the audible humming or buzzing sound that most electric fuel pumps make for a few seconds when the ignition is turned on. If you don't hear this sound, it could indicate a faulty pump or a blown fuse. Checking the fuse is a straightforward task and should be done first.

If the fuse is intact or replacing it doesn't solve the problem, you may need to perform additional tests, such as checking the power and resistance at the pump using a DVOM or test light. You can also visually inspect the pump flow by connecting a fuel line from the pump to a water bottle and observing the fuel flow when the pump is activated. If there is no fuel flow or only a weak flow, the pump likely needs to be replaced.

It's important to consult your ATV's manual for specific instructions and safety precautions when performing any diagnostic tests or repairs.

Frequently asked questions