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Diesel Tractor Starts But Won’t Stay Running: Fix-It Guide

Diesel Tractor Starts But Won’t Stay Running: Fix-It Guide

Diesel tractors don’t have the same points of failure that gas tractors do: no spark plugs or rotors to replace, and no carburetors to get filled up with sludge. They’re also designed to last longer and give off a higher power output. But they are are still combustion engines and prone to occasional problems.

If your diesel tractor is starting but won’t stay running, you likely have an issue in one of the following areas:

  • a pressure imbalance, reducing fuel-burning potential
  • an impediment in the fuel system
  • environmental conditions causing diesel gelling or moisture in the tank

The rest of this article will review some potential reasons why your diesel tractor starts and then shuts off, and what you can do to troubleshoot. 

Pressure Issues

Diesel tractors have internal combustion engines, which utilize high temperatures and high pressure to turn liquid diesel fuel into vapor to run the machine.

If there is a pressure imbalance within your engine, it won’t be able to properly vaporize the fuel at the rate it needs to, resulting in a tractor that may start, but won’t run

There are a few things that could be impacting the pressure of your tractor engine, ranging from the fuel pump to the various lines that go in and out of the pump. 

Fuel Pump

The first thing you’ll want to check when troubleshooting a diesel tractor that starts but won’t stay running is the pressure of the fuel pump. Too much or too little pressure within the fuel pump can cause issues. 

To identify if you have too much pressure inside the fuel pump, you’ll need to conduct a test to allow additional air to filter inside. 

To test this, loosen the screws on the timing cover, allowing some fuel to leak out. Once you’ve done that, start the engine again and see how it runs.

If your engine runs fine for a while with the loosened timing cover, you likely will need to replace the fuel pump.

This YouTube video walks through the process for replacing a diesal tractor fuel pump:

If the symptoms remain the same, and your tractor starts, then suddenly stops running, you’ll need to move on to another area of the fuel system. 

Return Lines

The next thing you’ll want to check relative to engine pressure is the return lines. Check to see if there are cracks or splits in any of the return lines that may impact how much fuel is filtering through your fuel system. Check the seals at the base of these lines, as that could also contribute to a pressure issue. 

You can also disconnect the return lines and blow compressed air through them to check for leaks or cracks. If you feel air coming from any point of the line other than the ends, you may need to replace them.

Injection Lines

Fuel injector lines are what delivers the pressurized fuel from the injection pump into the fuel pump. If there is a leak somewhere in one of these lines, it can prevent sufficient fuel from entering the injection pump. These lines are specifically designed with more durable material to handle the higher pressure, which can reach up to 50 PSI, but they can dry out and crack over time.

To check these lines, visually inspect them like you would the return lines. Is the material worn down in places? Are the clamps securing the lines in place to the fuel pumps rusted or loose? These are all signs that you should look into replacing these lines. 

Fuel Issues

When a diesel tractor starts but won't stay running, fuel issues can often be the source of the problem.

If you’ve verified that there are no pressure issues with your tractor that would cause it to start and then suddenly shut off, it’s time to move on to potential fuel issues. If your tractor’s engine isn’t getting enough fuel, it may start, but it won’t continue to run. You’ll need to check the various aspects of the fuel system to rule this out. 

Fuel Lines

There could be a clog in the fuel line that prevents enough fuel from getting into the pump. To check this, carefully disconnect the lines from your fuel pump and drain them out.

If diesel fuel is pouring out, you can be fairly certain that there are no clogs. However, if the fuel is dripping out slowly, there may be something in there.

This YouTube video, the author explains how this simple and often overlooked problem of a clog in his tank could have resulted in a lot of unneeded expense had he not checked this.

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Using an air compressor, blow air into the line to dislodge whatever bacterial algae, dirt, or leaves may have obstructed the line.

Once you’ve done this, fill your tractor with additional fuel and bleed the lines before starting it again. 

Fuel Filter

Another common cause of tractor failures is a clogged fuel filter. This should be one of the first things you check when evaluating your fuel system and be a part of your regular maintenance schedule.

First, conduct a visual inspection of the filter – does it look black, and is there a sort of slimy, thick substance on the inside? If yes, you will need to replace it to be on the safe side. 

To replace the filter, pinch the hoses on either side of the filter, and then remove the clamps that secure the lines. Loosen the bolt that secures the filter bracket, then carefully remove the filter.

Place the new filter in the same direction as the one you removed, reconnect the lines and secure the brackets and you should be good to go. 

Fuel Pump Filter

I mentioned the fuel pump earlier regarding pressure. Another source of potential clogs in a fuel system is the screen within the fuel pump itself. This filter is meant to catch things like dirt, debris, and other organic material that aren’t meant to be in the fuel tank, so it’s bound to get clogged up now and again. 

To check inside the fuel pump, you’ll need to bleed the fuel pump, and then utilize compressed air to push anything out that may have been clogging the filter. 

Other Things to Consider

There are other things to consider when troubleshooting why your diesel tractor won’t stay running after you’ve started it, such as environmental conditions like temperature and humidity. 

Temperature

If you live in an area that gets very cold, your tractor may have a hard time starting up and running smoothly. At lower temperatures, diesel fuel can gum up and cause real headaches. This is commonly referred to as “diesel fuel gelling” (source).

This can cause issues as the engine will need to work harder than normal to process the fuel. Over time this can cause permanent damage to your tractor.

One of the best preventative measures for this is the use of a diesel fuel conditioner and anti-gel (link to Amazon).

Humidity

In more humid climates, humid air can lead to condensation in the lines of your tractor’s fuel system, which can cause major issues.

If water gets into your fuel system, it can mix with the diesel fuel and cause issues.

Conclusion

To review, several factors can contribute to a diesel tractor continuously shutting off after starting. Pressure and fuel issues are the biggest culprits, but environmental factors can play a role as well. 

  • To troubleshoot potential pressure issues, check the fuel pump, the return lines, and the fuel injector lines for cracks or breaks. 
  • To troubleshoot potential fuel issues, check for clogs in the fuel filter, fuel lines, and even fuel pump. 

Remember that factors such as temperature and humidity can also play a role in your tractor’s engine system.

eManualOnline provides descriptive, affordable and convenient service and repair manuals for cars, trucks, tractors, motorcycles, and more. Download one today. (link to eManual Online).

Related Reading: Tractor Runs But Has No Power (Gas & Diesel Engine Issues)

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