If your ATV engine is not getting enough fuel, it won’t run properly. You’ll notice it bogging down and just not having the power it used too. If you’re not getting fuel to the engine at all, it won’t even start for you.
The most common reason an ATV engine is not getting fuel usually has to do with the carburetor. Either a stuck needle valve or a loose or cracked vacuum hose are the most common issues. Don’t worry, there are pretty straight forward things you can do to check where your problem is.
There are a few different reasons you may not be getting fuel to your engine. It’s not that hard to check the parts to see if their working properly. I recommend going step by step checking one thing at a time, eliminating possible issues as you go.
If you have a fuel injected engine, you can skip this next part and jump straight to the fuel injectors, fuel pump, and compression check sections.
Check The Carburetor
I would first check the carburetor to help narrow down where you should start your investigation. All you need to do is spray a little carb cleaner or ether down the carb and see if your engine will fire up with that. Or you could pour a little gas in the carb and try to start it up.
If it does start, and then dies right away, at least we know now it’s a problem getting fuel to the carb. We know that now because, when the carb has fuel, the engine will run. You should check to make sure fuel is getting to the carb now.
If it still doesn’t start at all, you may have a problem getting fuel from the carb to the engine. That is telling us the problem is further down the line. It could be an issue with compression if that’s the case.The engine doesn’t have enough compression to pull in the fuel it needs and stay running. I will go over how to do a compression check later in this article.
Another check to do with the carburetor is to adjust the idle mixture screw. I know it sounds too good to be true, but a lot of times this adjustment isn’t set right so the engine isn’t getting the right air/fuel mixture to run properly.
Is The Carb Getting Fuel?
Ok, you sprayed something into the carb and the engine started up for a few seconds. Great, now we need to make sure the carb is getting the fuel it needs for the engine to run. Disconnect the fuel line going into the carb and put that end into a bucket or something to catch the fuel.
You may need to take out any spark plug, or just unplug them, just in case. And try to start the engine and look to see if fuel is coming out of that fuel line. If there is, then you have no problems getting fuel from the gas tank and it is probably a needle valve or float problem.
If there’s no fuel coming from the tank down that fuel line, then you’re problem may be an issue with the fuel pump, if you have one, or an obstruction in the fuel line or shut off valve. I will go over how to diagnose the fuel pump later in this article.
Needle Valve And Float
If the needle valve in your carb is corroded, it will not allow fuel to flow to the engine properly. Same thing will happen if your float is getting stuck. You’re going to need to clean the carburetor and possibly replace those parts if they’ve gone bad.
First remove the float bowl to gain access to the carburetor insides. Then you can remove the pin holding the float in place. Before you do that, you can try moving the float up and down with your hands, the float should move freely and have no resistance feeling when moving it.
The needle valve will be attached to the under side of the float, here is a picture of what you’re looking for. You can try cleaning the needle valve using carb cleaner. Just soak the thing and let it sit in carb cleaner for a few hours.
If that didn’t help, or you just don’t want to do it, no big deal. Needle valve are pretty cheap online. Here’s an example of a Carburetor Float Valve Needle on Amazon to give you an idea of what you’re looking for.
You can also replace the float if you want to, usually you don’t have to but i would give it a good cleaning. Double check all the seals and everything since you’ve got the carb open, and clean out everything really good.
Check the bowl gasket, if this was bad, you would have noticed the carb leaking fuel before. To check and replace the valve seal, you’ll need a pick or something to pull it from the carburetor. I’ve used a sheet rock screw before. Just thread the screw in a little and pull out the seal.
Check out the picture for an idea of what you’re looking at. Once you’ve removed the old seal, insert the new one and make sure it’s seated all the way.
You can do that with a metal punch or something, just make sure you don’t hit too hard because you could break the aluminum frame of the carb. Reassemble with new needle valve and you should be good to go.
Check Fuel Injectors
Fuel injectors can get gummed up after a while if they aren’t cleaned regularly. The end of the fuel injector has small holes in it that the fuel passes through, creating a spray that enters the cylinder. If those holes get gummed up, the spray will be off, and you’re engine won’t run.
If you think it could be a problem with your fuel injector, I’d recommend trying to clean them first before buying new ones because they can be pretty expensive. First, you’ll have to remove the fuel lines that hook to the fuel injectors.
You could always remove the fuel injectors completely and let them soak in some fuel injector cleaner. I use this B-12 Chemtool Thru-Rail Fuel Injector Cleaner but you can use any carb cleaner / fuel injector cleaner you want to.
If you don’t want to remove the fuel injectors completely you can try another method. You will still need to remove the fuel lines and let all the gas drain out of them. You will then fill the fuel line with fuel injector cleaner, and then reconnect the fuel lines.
Try starting the engine for at least 20 seconds. If it does start, don’t let it run for longer than 20 seconds. Then you want to sit and wait about 10 minutes or so. You need to give the fuel injector cleaner time to do its work. Repeat the process five more times, but only try to start for 10 seconds, and then let sit for ten minutes.
I know it’s not the official way to clean the injectors, but I’ve seen it work, and it can save you from all the work of removing the injectors. Once you get the quad running, you’re going to want to add a fuel additive to your gas to keep the injectors clean.
You should be doing this at least once a year anyway. I do it with my maintenance checks before spring begins every year. I usually just add some of this Gumout Complete Fuel System Cleaner to the gas tank before I start it up for the season.
Is The Fuel Pump Working?
I would say to try blowing air through the fuel pump to make sure fuel will be able to flow freely through it. But if you have a vacuum operated pump, you won’t be able to do that. There are diaphragms in there that could get damaged.
To make sure you’re vacuum operated fuel pump is working correctly, pull the vacuum line to the fuel pump off and crank the engine. You should feel a good amount of suction at the mouth of the carb.
The engine crates a vacuum pulse to the fuel pump, which in turn creates an amount of pressure that pushes fuel into the carburetor. If you’re not getting good suction, try replacing the diaphragms in your fuel pump and make sure your vacuum lines aren’t cracked.
If you can, try cleaning the fuel line out and replacing the fuel filter to make sure you’re getting fuel to the carburetor. Inspect the fuel pump for wear and loose or cracked hoses. If there is no vacuum in the hose, you’re carb won’t get any fuel. This is most likely caused by a crack in the vacuum fuel lines or a bad fuel pump.
You may find it easier to just replace the fuel pump all together since they aren’t usually very expensive.
The compression check is pretty straight forward, you’re trying to see if you’re engine can handle the right compression to run properly. Without compression, you won’t get fuel and your ATV won’t start.
The steps are pretty simple if you have a compression tester kit. Basically, you remove the spark plug, hook up the compression tester and run the test. You just have to make sure your engine is at the down stroke in the compression cycle.
I go over this process in a lot more detail and explain step by step how to perform this test in my article, Top 7 Reasons An ATV Smells Like Burning Oil. If you weren’t getting good compression, but enough that the quad still ran, you would leak oil into the cylinder. Go to that article and scroll down to the leak down test section for a step by step guide on checking for compression.