As reliable as Kubota tractors are, they do have certain idiosyncrasies. One of those is a common issue of the tractor shutting off suddenly while in use. Here’s what I’ve learned about why this happens and how to deal with it.
If your Kubota tractor is starting OK, but then shutting off, you most likely have an issue with fuel starvation. You will need to check for fuel and/or airflow issues by checking the fuel filter, pump, and lines, as well as the air lines and air filters.
The rest of this guide will outline the types of issues you may come across when troubleshooting your tractor and what to do to fix them.
Note: This is a focused review on this issue for Kubota tractors. For more comprehensive walkthrough not specific to Kubota, see Diesel Tractor Starts But Won’t Stay Running: Fix-It Guide
Fuel Flow Issues
To be used as energy in an oil-powered machine, fuel needs to flow through the engine via a process known as combustion. Through this process, fuel is taken in its liquid state and broken down into very small molecules.
Those molecules are then mixed with air, and change from a liquid to a gaseous state, also known as vaporization (source).
It is this process that allows an engine to metabolize the fuel and use it to power the machine. If there is not enough fuel or air flowing through the engine, fuel starvation is the result.
In scenarios where a tractor is starting fine, but then stalling and shutting off, the most obvious place to begin troubleshooting is the fuel system. This includes the filters, the fuel pump, and the lines connecting the two.
To troubleshoot efficiently, you should start with the smallest piece first, and work your way up to the more complex components of your tractor’s fuel system. In this case, that would be the fuel lines.
Start by disconnecting the line from your fuel filter to your fuel pump. Is diesel fuel pouring out, or is it barely trickling as it leaves the line? If it’s the former, there could be something clogged in the line.
Use an air compressor to flush some high-powered air into the tube in question.
If fuel begins to pour out, you know that there was a clog somewhere – either in the line itself or potentially in the screen of the fuel pump. If this is the case, be sure to bleed the fuel pump before reconnecting the lines.
If you’ve checked the fuel lines and you’re still experiencing issues, the next thing you’ll want to check is the fuel filter. This portion of the fuel system acts as a screen, protecting the internal portions of the engine from dirt, sludge, and other loose particles that can damage the engine if they get inside.
Most fuel filters are on the side of the tractor, but some tractors have their filters underneath the engine. If you are unsure about yours, the Kubota website has walk-through videos based on your tractor’s model.
You can also download a service manual for your Kubota tractor (link to emanualonline).
The first thing you’ll want to do is visually inspect the filter. Is it filled with what looks like a thick, viscous mud? If the answer is yes, you should purchase a replacement.
Replacing the fuel filter is a fairly simple process, you just need to be sure to pinch the lines connecting to it before you remove it, so you don’t spill fuel all over you or your tractor. You’ll be able to remove the filter and replace it in about 10 minutes or so.
This YouTuber does an excellent job of walking you through the process visually:
Fuel Injector Pump
If you’ve checked your fuel lines, and you’ve checked your fuel filters, and you’re still having issues with your Kubota tractor starting and then shutting off, it’s time to check the fuel pump.
Your fuel pump is one of the most important parts of your fuel system because it’s what pulls the fuel from the tank into the engine. As you may recall, this is where combustion takes place.
If the fuel pump has a block in it, this is going to prevent fuel from being converted to power. There is a screen built into the fuel pump that can become clogged by things that were missed by the filter, such as dirt, water, and even leaves or pine needles.
Blockages caused by trapped air can also impact the pump’s ability to inject fuel into the engine.
To check the fuel pump for blocks, you’ll need to bleed the injector pump by disconnecting one of the lines from the pump. This YouTube video demonstrates the process:
If the components of the fuel system are in proper working order, you may have an electrical issue with the unit responsible for the emergency fuel shutoff device, also known as the fuel solenoid.
This unit acts as a failsafe in case of temperature spikes or abnormal electrical issues while running your tractor, and will stop fuel from flowing to the engine in the event of an emergency.
To determine if this is causing your issue, check the wires of the solenoid and ensure they are connected properly. They may look as though they are connected but might be loose, causing a misfire in electrical currents which can lead to unnecessary fuel shutoffs.
Try disconnecting the wires and see if the tractor still shuts off. If not, you may need to replace the solenoid.
As mentioned earlier, proper airflow to an engine is just as important as the flow of fuel.
- If you have too much air, pressure issues can arise in the fuel pump, which will cause issues with fuel injection into the engine.
- If you have too little air, combustion won’t occur at the rate you need it to.
When troubleshooting a potential airflow issue, you’ll first want to take a look at the air filter. Much like the fuel filter, an air filter on a Kubota tractor removes dust, bugs, grass, and other particles you don’t want ending up in your diesel fuel.
If the air filter becomes clogged, airflow to the engine will become limited which can also result in fuel starvation.
To check the air filter, remove the filter cap and tap out any visible dirt. Next, remove the filter and use compressed air to blow out the majority of the dirt trapped inside.
Inspect the filter for any tears that may be causing debris from getting inside the engine. Once you’re finished, replace the filter and try to start up the tractor again.
Here’s a detailed overview of air filters for Kubota tractors:
Although technically part of the fuel system, return lines can cause issues with airflow just like an air filter can.
If a return line has a crack or a break in it, excess air can escape from the line, diminishing the pressure inside the engine that is required to convert the diesel fuel to power for the tractor.
To check the return lines, visually inspect them for breaks or cracks. If you don’t see anything, try disconnecting the lines, one at a time, and blowing compressed air into them. If you feel air leaking out, you now know you need to replace that line.
To review, if your tractor is experiencing symptoms where it starts fine, but then suddenly shuts off, you most likely have a fuel starvation issue caused by lack of air or lack of fuel to the engine.
This can be caused by several variables within the fuel system itself, but it can also be caused by an airflow issue.
To check your tractor to determine if you have a fuel system issue or an airflow issue, you’ll want to check the following components of your Kubota engine:
- Fuel Lines
- Fuel Filter
- Fuel Injection Pump
- Fuel Solenoid
- Air Filter
- Return Lines
Didn’t solve your problem? See these articles for more insights: