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As with any internal combustion engine, you may run into problems every now and again with your ATV or UTV.
Fortunately, tracing and troubleshooting the issue is often simple. This page will go over some of the most common reasons why your ATV won’t start or why it is running poorly.
You can find more motorcycle and ATV maintenance and repair topics throughout other sections on MotorcycleZombies.com.
Reasons Why Your ATV Won’t Start
There are only 3 things that your ATV’s engine needs to run. They are:
As long as those three things are present, your quad should start up.
However, within each of those categories there’s always room for errors. We’ll cover how to troubleshoot each one below.
Before you get started, try to approach the problem with a systems-oriented approach:
- Check if fuel is flowing and getting through the carbs.
- Check that the spark plugs are firing and the battery is fully charged.
- Check that the engine cylinders have enough compression and there are no vacuum leaks in the circuit.
But, before you start diving into the real diagnosis, you should always check the simple things first, including:
- That there is fresh fuel in the gas tank.
- That the fuel valve is in the “ON” position.
- That the key, ignition, and kill switch are in the correct position.
- Make sure the transmission is in Park or Neutral.
Once you’ve checked the simple fixes, it’s time to move on to further troubleshooting why your 4×4 won’t start.
A No-start condition caused by electrical problems is typically one of the quicker ones to diagnose and fix.
In most cases, the problem will come from the battery.
First, make sure that the battery is fully charged, connected, and giving the appropriate voltage reading.
A dead or weak battery may not be able to provide enough power to start your quad.
You can learn more about how to charge an ATV battery here.
Next, check that the main fuse is not blown.
If the battery and fuse are good, you can then confirm that the spark plugs are firing.
To do so, remove one of the spark plugs from the engine and lay it on a metal engine cover. Press the starter and look for a strong spark coming from the plug.
If you see no spark, you can check to make sure the plug gap is properly set or try replacing the spark plug.
If nothing happens when you press the starter, there may be an issue with the CDI box or starter solenoid.
ATV CDI Box Problems
What is a CDI Box on an ATV?
A CDI Box controls when the spark plug should fire based on the position of the pistons and crankshaft.
CDIs can degrade and stop working.
A bad or faulty CDI can cause misfires or no-start conditions.
If you suspect your CDI Box is the problem, you should first rule out all other electrical issues.
After that, it may be best to replace the unit altogether.
ATV Starter Solenoid Problems
If the starter motor is not turning over when you press the start button, there may be an issue with the solenoid.
The starter solenoid should give off a loud “click” when you press the starter. If there’s no click, the solenoid may be bad or there may be an issue with the wiring.
You can test your ATV solenoid with a multimeter to confirm whether or not it is getting power.
To test a solenoid:
- Set your multimeter to measure for continuity.
- Place the positive (red) lead on the positive post of the solenoid.
- Place the negative (black) lead on the negative post.
- Disconnect the wires from the solenoid to the starter motor.
- Send power to the solenoid by pressing the start button.
- You should hear the solenoid click.
- The multimeter should read a connection between the positive and negative terminals.
Another way to test the solenoid is to manually bridge the posts with a screwdriver. If this starts the engine, the solenoid may be bad or there may be a wiring issue within the ignition circuit.
When a solenoid goes bad, the circuit will not fully close when the starter is pressed. This can be caused by a faulty solenoid, loose connections, or broken/corroded wiring.
Find more topics about electrical and charging system issues for your ATV here.
Fuel issues causing a no-start condition can originate from the gas tank, petcock, fuel lines, or carbs.
It’s best to start from the gas tank and work your way down through the fuel system.
First, confirm that there is fuel in the tank. Note that old fuel can sometimes cause starting problems as well.
Next, check to see that fuel is moving through the fuel lines and reaching the carbs.
Finally, you can check that fuel is reaching the combustion chamber. This can be achieved by turning over the engine without starting it and removing the spark plug to check for gas. A dry spark plug would indicate that gas is not reaching the combustion chamber.
The most common cause of a fuel issue that is resulting in a no-start condition is due to dirt or clogged carburetors.
For fuel injected vehicles, check that the fuel pump is clean and operating properly.
Find more topics about ATV carburetors and fuel systems here.
Air & Compression Issues
Finally, you’ll need to make sure that the fuel/air circuit is working properly and that there is enough compression in the combustion chamber.
Make sure that the air filter is clean and properly installed without anything blocking the intake.
Also check that there are no leaks in any of the manifolds, gaskets, or mounting areas.
Make sure that the exhaust headers are secured tightly.
If all of the above check out, you can run a compression test to check the ATV engine and perform a leak down test.
If there is not enough compression within the cylinder, the combustion cycle may not work. Common causes are worn cylinders, worn piston rings, or leaking gaskets.
ATV Running Poorly
If your ATV starts, but runs poorly, you’ll have a little more troubleshooting to do.
Poor running conditions often boil down to one of the following:
- Carbs running rich.
- Carbs running lean.
- Problem in the fuel/air circuit.
- Ignition timing issue.
- Weak spark issue.
If your ATV sputters or bogs on acceleration, you’re likely looking at a rich or lean running conditions.
You’ll need to make sure the carbs are cleaned and properly tuned.
Other things to check if your ATV is running poorly, include:
- Battery fully charged.
- Air filter clean.
- Throttle cable free play properly adjusted.
- Oil has been changed at regular intervals.
- Gasoline is good.
A well maintained and serviced ATV will run better for longer than a neglected one.
Find more motorcycle and ATV troubleshooting tips here.