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How to Start a Diesel Tractor That Ran Out of Fuel | All-In-One Guide

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Nobody runs out of fuel purposefully. But we homesteaders do often tempt fate. Right? Luckily – the solution is simple if a modern diesel tractor with an electric diesel pump runs out of fuel. Fill the tank and start the engine. 

But starting a diesel tractor with a mechanical fuel pump is different. You’ll have to fill the tank and bleed the fuel line

Bleeding a diesel tractor fuel line can be intimidating for the uninitiated, but with these guidelines, your old tractor will be back in service – with no sweat.

An old school red tractor resting along a grassy field.

How to Start a Diesel Tractor That’s Run Out of Fuel

When a diesel tractor with a mechanical fuel pump runs out of fuel, the best way to restart the engine is to bleed the fuel lines. Fill the tank with diesel and loosen the fuel filter and pump bleed screws. Then prime the fuel lines to remove air bubbles. Tighten the bleed screws and crank the engine until it starts.

The video below shows you some of the vital steps to take to bleed your diesel tractor. Find the full instructions below. And if you have any questions, please leave a comment! Dan is more than happy to help out.

Starting a Diesel Tractor That Ran Out of Fuel

Fuel lines on diesel tractors differ in the following ways.

  • Older tractors have a mechanical injector pump. And often, a mechanical lift pump draws or pushes fuel from the diesel tank, through the filters, and into the injector pump that supplies the engine with high-pressure (atomized) diesel. 
  • Modern tractors typically have an electronic lift pump supplying an electronic injector pump.
  • Diesel tractors may have more than one fuel filter.

To successfully bleed a diesel tractor fuel line, ensure the tank is filled to a level higher than the primary fuel filter to allow gravity to create the necessary downward pressure to push fuel through the filter to the lift pump. 

  • Follow a sequential process of bleeding the fuel filters, priming the lift pump manually, and cracking the injectors to purge the fuel lines of airlocks.
  • Crank the engine to build the necessary pressure to bleed the injector lines. 
  • Tighten all bleed screws/nuts/plugs and injector lines to prevent fuel and air leaks.

What Happens When You Run a Diesel Tractor Out of Fuel?

Your diesel farm tractor will shut down when it runs out of fuel. But any agriculture mechanic will tell you what happens next is a bit of a wild card. That’s because when your diesel engine (whether a diesel pickup or farm tractor) runs out of fuel, the fuel pump might suck air instead of diesel fuel. With air jammed within the fuel system or fuel hose, farm tractors need to push that air out before it will run – an action called fuel system bleeding. Bleeding your engine may require a professional mechanic qualified to service heavy equipment. However, some diesel engines have self-bleeding systems in place. We have a few tips that can help you in any case.

When a diesel tractor fuel tank goes dry while the engine runs or during the starting procedure, the air gets sucked into the fuel lines. The sucking air creates an airlock, which deprives the fuel pump of hydraulic pressure, rendering it incapable of pumping fuel to the engine.

  • Large diesel tractors have long fuel lines leading from the diesel tank to the high-pressure injector pump. The long fuel lines make bleeding a lengthy process.
  • Smaller diesel tractors have shorter fuel lines and are easier to bleed.

Remember: Running your tractor till the tank runs dry can damage the engine. Why? Diesel supplies the necessary fuel for combustion. And diesel is also a lubricant for the injector pump, diesel injectors, and engine components.

How Do You Start a Kubota Diesel Tractor After Running Out of Fuel?

A Kubota diesel tractor that has run out of fuel and stopped will require bleeding the fuel lines between the diesel tank and pump.

  • Typically, small Japanese diesel tractors like Kubota and Yanmar don’t need bleeding at the injectors, just at the fuel pump. 
  • Does the tractor have an electric fuel pump? Then you won’t need to bleed the lines. Instead, fill the tank with fuel, start the engine, and the electric fuel pump will supply the fuel lines with diesel. 
How to Bleed Diesel Fuel Lines In Small Tractors
Here’s a quick tutorial sharing how to bleed diesel fuel lines in a compact farm tractor. The tutorial is under five minutes and gives you a general idea of what to expect. We also cover more details below.
blue farm tractor sitting idle in the field
Imagine this farming scenario. You’ve been running your Ferguson 168, John Deere tractor, or compact tractor all morning. After plowing for hours, you can see the finish line. Only a few more minutes! But suddenly, the low fuel gauge or fuel level meter starts flashing yellow. Drats! Your tractor needs fresh diesel. But instead of filling up – you try to finish the work without refilling. This time, you didn’t make it. Now you need to learn how to start a diesel tractor that ran out of fuel. Step one is to try bleeding the fuel system. Luckily, in some cases, you don’t need to be a diesel mechanic to get it done. Here’s how.

How Do You Bleed a Diesel Tractor Fuel System?

To bleed a diesel tractor fuel system, follow a sequential process of removing airlocks from the fuel lines using pressurized diesel from the refilled diesel tank. 

The necessary pressure to remove airlocks will be obtained by manually priming the lift pump for low-pressure lines (before the injector pump) and by cranking the engine (for high-pressure lines from the injector pump to the injectors). 

Bleeding the fuel lines and fuel filters on a diesel tractor
Bleeding the fuel filter and fuel lines is a messy job. That’s one reason we always recommend keeping spare jerrycans on hand with plenty of diesel fuel. It’s the easiest way to avoid extra work! But if all else fails, follow the easy steps below.

Bleeding a Diesel Tractor Fuel System – Step by Step

  1. Fill the diesel tank with fuel higher than the primary fuel filter.
  2. Bleed (aka prime) the fuel filters (primary and secondary). Open the bleed screws one by one on the filters and follow the line to the hand primer at the lift pump. 
  3. Use the lift-pump hand primer lever to pump fuel through the lines with one bleed screw at a time opened slightly. 
  4. Pump until fuel flows out of the filter bleed hole – and until no bubbles are visible.
  5. Close the bleed screw. 
Here’s Dan! He’s bleeding the fuel lines and filter until the fuel comes out.

Bleeding the Lines to the Injector Pump

  1. Remove the bleed plug from the injector pump and pump fuel through the lines with the hand primer until a strong fuel stream flows from the bleed hole and no air bubbles are visible.
  1. Put the pump bleed plug back in the bleed hole.

Bleeding the High-Pressure Injector Lines

  1. Crack the injector nuts by half a turn, one at a time.
  1. Put the fuel stop in (in older tractors).
  1. Crank the engine until a strong fuel jet exits each injector line (one at a time).
  1. Work through each injector line one at a time, purging all air bubbles.
  1. Tighten each injector nut tightly after bleeding. 
Cracking the injectors on a diesel tractor than ran out of fuel
Here’s Dan cracking the injectors on a diesel tractor than ran out of fuel.

Warning: Diesel exiting the injector lines during bleeding has insanely high pressure (+15,000 PSI, pounds per square inch). Whoever is bleeding the lines should stand well away from the tractor when the engine gets cranked to bleed the injector lines.    

How to Prime a Fuel Pump On a Diesel Tractor?

Priming a diesel fuel pump requires removing all air trapped in the fuel line, from the diesel tank to the injectors. 

  • Loosen the bleeder screws (on fuel filters and diesel pumps), and pump fuel through the lines using a hand primer or by cranking the engine.  
Dan is bleeding the fuel filter on a diesel tractor.

How Do You Bleed Air Out of a Diesel System?

You bleed air from a diesel system by priming each filter and pump in the fuel line. 

  • Loosen bleed screws on the fuel filters and injector pump.
  • Pump diesel through the lines using a hand primer pump or by cranking the engine.
  • With its bleed screw open, each component will get primed – purged of air trapped in the diesel system.

Diesel from the fuel tank is pumped through the fuel lines by:

  1. A primer or lift pump, operated manually or mechanically, for low-pressure fuel delivery to the injector pump.  
  2. The tractor crankshaft (cranking the engine) powers the injector pump, producing (the necessary) high pressure for the injector lines.
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06/12/2024 07:12 am GMT

How Do You Bleed a Fuel System on a Kubota Tractor? 

To bleed a Kubota Tractor fuel system, fill the tank with diesel, bleed the fuel filters using the primer pump, and crank the engine until the engine starts.

Smaller tractors generally only require bleeding up to the injector pump. In other words – there is no need to crack the injectors.

How Do You Start a Diesel Engine After Replacing a Fuel Filter?

After replacing a fuel filter on a diesel tractor, open the bleed screw on the filter housing and allow the fuel to flow out for a few seconds. Then retighten the bleed screw.

  • Use the primer lever on the lift pump to create the necessary pressure to draw fuel through the lines.
farmer loading=
Here’s the best way to avoid engine bleeding or fussing with the correct fuel pressure. Keep some clean fuel nearby! In other words – don’t let your diesel engine run out of diesel fuel in the first place. It’s the first thing we tell anyone riding our diesel tractor. These five minutes of preparation can save you an annoying headache later on. (If you’re not mechanically inclined, bleeding the diesel engine can cause a huge fuss. It’s trickier than fixing a dead battery or changing a tire. So – never let your diesel run out of fuel!)

How Does a Diesel Primer Pump Work?

Diesel primer pumps can either have a diaphragm or a piston and plunger to build pressure in the fuel lines. Diesel primer pumps can be operated manually or by cranking the engine.  

  • Diesel primer pumps are perfect when bleeding the fuel lines on diesel tractors with mechanical lift pumps.
  • Hand primers are a manual way to pump fuel through the fuel lines and purge air from the system.
  • Fitting an electric fuel pump will solve most fuel line issues.

Read More!

antique tractor in the field standing by ready to work
We have one more tip for anyone using diesel engine farm equipment. Never forget the trouble a clogged fuel filter can cause! Diesel engines are much more resilient and longer-lasting than gasoline engines. However, diesel engines aren’t perfect. Diesel engines have somewhat fragile fuel injector systems. Dirt particles, gunk, and muck can throw a significant wrench into the works. We try to check our dirty fuel filter every 100 hours of use. Luckily, fresh fuel filters are cheap. And they can save you a ton of frustration, heartache, and downtime. Your four-cylinder diesel engine will thank you for your courtesy. We guarantee it.

What Is Airlock In a Diesel Engine?

Airlocks are trapped air pockets in the lines between the various components of the diesel system, including the fuel tank, the primer pump, the injector pump, and the injector lines.

  • A cracked fuel line will suck in the air and must get replaced. 

Tip: By installing an electric lift pump near the diesel tank and bypassing the mechanical lift pump, you will eliminate the need to bleed the fuel system in your tractor!

Can You Flood a Diesel Engine?

A flooded diesel engine is an uncommon occurrence and is usually a result of a severely blocked air intake filter.

Conclusion – All Bled Out

If the diesel gods run out on you and your tractor runs dry, don’t panic! You now have the dope on resuscitating your workhorse with minimal sweat. If you own an old tractor, invest in an electric lift pump for a no-bleed machine. Or keep a beady eye on those tank levels!

Tractor on!

old blue tractor in a citrus orchard
Bleeding air from diesel filters and your fuel hose is tricky. We hope our detailed steps help make the process easier. It’s also something we study continually. We found an excellent guide published via the Utah State University Coop Extension. It teaches how to bleed air from diesel fuel lines in 15 steps. We printed this out and pinned it to our workshop wall and refer to it when we get stuck, need motivation, or need to double-check our thought process. It’s perfect if you run out of diesel fuel, change the diesel fuel filter, or interrupt the diesel fuel system in any way. And it’s a lifesaver when you need it. We also share more resources below. We hope they help!

How to Start a Diesel Tractor That Ran Out of Fuel – References, Field Guides, and Works Cited:

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