Diesel Injection — When Even the Best Small Farm Tractor Fails

How to Get the Most Common Farm Equipment Going Again

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Diesel Injection — When Even the Best Small Farm Tractor Fails

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Click Click, Click Click … I’ve come to really hate that sound this year. Our 15-year-old John Deere 5105 (one of the best small farm tractors) has been causing us a lot of grief lately, including leaving me hopelessly stranded in a pile of snow last winter and dying on me when I was mowing a field a good mile away from my tools.

Click Click, Click Click … That’s the starter telling me that I’ve officially drained the battery of all its go juice, again.

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Diesel tractors are some of the best small farm tractors and a fantastic addition to any homestead, and once you have a tractor with a bucket loader, you’ll wonder how you ever managed without one. But just like any equipment, they break, they fail and they disappoint you from time to time, but the good news is; most fail-to-run problems in diesel engines are usually one of only four issues.

But First, A Quick Primer on Combustion

Combustion is the process of burning something, or more technically put, a rapid oxidation of fuel that releases energy in an exothermic manner. All combustion engines rely on the energy created when whatever fuel they use goes boom (combustion) inside their cylinders, which pushes down on the piston and makes the crank shaft go round and round. In order to achieve combustion, there are three things that have to exist, which is commonly referred to as the combustion triad; fuel, air, and ignition. Without these three things, your engine won’t run, your furnace won’t make hot water and your wood stove won’t make heat, so this theory applies to both your best small farm tractor and machinery, wherever fuel is burned to produce energy.

In a combustion engine, there are two types of ignition sources which are electronic (spark) ignition like you see in gasoline engines with spark plugs, or compression like in diesel engines. A diesel engine compresses its fuel and air so much that it creates heat, which causes the mixture to ignite and causes this exothermic reaction that makes these engines go round and round. Fortunately for us, unless your diesel tractor has been sorely neglected, beaten to death, or is very cold, we don’t need to worry about the ignition part of that triad.

The combustion triad. Unless these three elements exist, no combustion engine will run.

Typical Tractor Diesel Problems

The Starter: If you shut down your tractor, or it has been sitting for awhile and you go to crank it over but instead you hear that click-click noise, then you have a starter problem. That problem may simply be a dead battery that needs a jump, a corroded connection between the starter and the battery, or your alternator (or generator) is not charging your battery.

Your starter is a little electric motor with a gear that turns your engine over, and to do that it has to spin that gear as well as push it out to engage the teeth on the engine’s flywheel, so if you hear a fast whirring noise without your engine turning, then your starter is not engaging the flywheel. The likely cause of that is a stuck solenoid which prevents the gear from being pushed towards the flywheel. Almost all manufacturers say not to strike the solenoid when you think it’s stuck, but a quick rap of a hammer has saved me from walking home many times. If a tap on the starter does not fix the issue, then it’s time to buy a new starter. However, if your starter makes no sound despite a good battery or jumper cables, check to see if the starter is even getting power. Common causes of no power getting to the starter are blown fuses, bad key switches, and dead relays.


If your engine turns, but it can’t draw in air, it can’t achieve combustion. No combustion, no power, simple as that. Check your air filter(s) to see if it is clogged with sand, dirt or dust. Make sure rodents haven’t made a nest in the air intake and be sure there is a clear passage from the filter housing to the engine.

A fresh air filter in the filter housing. Not pictured is the second internal filter that fits inside.

Cold Engine Block

Even the best small farm tractor diesel engines do not like to be cold, period. Cold cylinder heads have a hard time making enough heat to achieve ignition, that’s why some engines have glow plugs, hot air induction units and possibly block heaters.

Glow plugs are small electric heaters that are screwed into the cylinder head(s) in a way similar to spark plugs, but they only create a little heat to warm the cylinder head up, not actually cause combustion. These do burn out occasionally and need to be changed every few years depending on how often they’re used.

Hot air induction, or hot air boxes, are common on newer tractors and basically consist of a heater element in your air intake system. When activated, the unit preheats the air that enters the engine and raises the cylinder temperature enough to cause combustion. Check your user manual for your tractor since this typically is not an automatic system, but a manual system you need to activate. On my John Deere 5105, you need to push the key in and hold for 3 to 5 seconds, then turn the key to start your engine.

This small aluminum block is the “hot air box”, also known as an air intake pre-heater.

Some of the best small farm tractors sold in cold climates have a 110v plug near the engine block to supply house electricity to a small block heater. This heater keeps the engine’s coolant somewhat warm so it will start in very cold environments, but it’s meant to be plugged in overnight, not 5 minutes before you need to start it. If your block is cold enough that it won’t start, plug it in and wait an hour or two. If we expect a bitterly cold night, we plug our tractor in and leave it overnight in case we need it to plow snow or run our generator if we lose power.

If worse comes to worst, spray a little silicone lubricant spray into the tractor’s air intake (without the air filter) and try to start it. Silicone spray will ignite before cold diesel will, so if you can get it to start the cylinder heads will heat up enough to run in diesel. Do not use ether spray to start a diesel tractor.

Fuel Supply

Fuel supply issues are the most common problems when dealing with a diesel engine that won’t run. Here are the most common fuel supply issues found in diesel engines:

Gelled Fuel

Unlike gasoline, diesel turns into a gel at around 17.5º Fahrenheit and will not flow through fuel lines. Even if your block heater is on, your fuel tank, lines, and filter can still get cold, so be prepared and have a bottle of diesel liquefier such as power service’s Diesel 911 product. Products such as these can be challenging to come by sometimes, especially when it gets cold, but check your local farm store, automotive parts store and nearby truck stops and grab a bottle or two just in case since that should be on your list of farm tools and equipment to have on hand.

Diesel De-Gelling products are a life saver. I found Diesel 911 on the shelf at my local NAPA.

Follow the instructions on the bottle, but most products work quickly by dropping some in the tank and fuel filter. Speaking of fuel filters, when diesel gels the wax in the fuel separates from the rest of the fuel and usually coats the fuel filter, rendering it useless. Be prepared to change your fuel filter when your tractor gels up and be sure to have one or two on hand. A big thanks to Walt the local mechanic for the waxed filter clue.

Algae Bloom

Sometimes in the warmer months, diesel and especially bio-diesel can experience a biological contamination that makes a dark slimy sludge in the tank and fuel lines. This slime typically caused by algae growing in the fuel clogs fuel filters and reduces fuel flow. Many companies make a biocide product for fuel to control this. If you store fuel on the farm, be sure to treat your storage tanks as well as your tractor’s fuel tank if this happens.

Contaminated Fuel

What are you using to store diesel fuel? Is it an old tank? Is it letting water in? Is it rusting inside? We have a 300-gallon fuel tank we keep diesel in on the farm and just recently we’ve noticed it became contaminated with all sorts of stuff. We’ve had to drain and inspect the tank and add fuel filters to our fuel transfer pump to prevent more contaminants from going into our tractor’s tank. If you find yourself with a badly contaminated tank of fuel on your tractor you may have to drain and flush your tank as well as clear your fuel lines. I use an air nozzle on my compressor to blow out obstructed fuel lines when this happens.


Water in diesel fuel can be deadly for an engine. Because of the high compression in the cylinder heads, introducing water with the fuel can destroy the piston heads. Because of this, most diesel fuel filters immediately swell when they come in contact with water, working as a cutoff valve of sorts. Since water is heavier than fuel if you drain the sump of your tank (the very bottom) and you find water after your tractor has mysteriously stopped working, then blow the fuel lines back into the tank, drain off the water and replace your filter before starting again.

The new filter setup on 2015 JD’s, a clear improvement from the style my 5105 uses.


Air is an important part of the combustion triad but in a diesel fuel line, it wreaks havoc on starting ability and performance. Every time you crack a line (open a connection point) you can introduce air into the system. If there is a leak in the lines, it may also be sucking air into the high-pressure lines, so find your leak and repair the line.

After performing any maintenance that required you to remove the fuel filter, open a fuel line connection or blow out a low-pressure supply line, you need to prime the line (fill it with fuel). Unlike electric fuel pumps in gasoline applications, air must be evacuated to get the engine to run. Some tractors have a hand pump near the fuel filter which allows you to draw fuel up from the tank and into the filter housing. If your filter housing situates the filter’s hole facing up like most applications, you can make your life easier by filling the filter with diesel before you install it.

Now that the low-pressure side of the fuel system is primed, you need to bleed (purge) the high-pressure injection lines that come from the injector pump and go to the injectors themselves. Most diesel engine manufacturers offer the crank and crack method, which is the typical method of trying to start your engine, which works the pump, and “cracking” or unscrewing the connection between the line and the injector with a wrench just enough to let the air and a little spurt of fuel exit, then tightening it back up. Do this to every injector and you should be able to start your engine. This method is time-consuming and requires two people, one to turn the key to crank the engine and another to crack the lines.

These connections between the fuel injector pump and the injectors themselves need to be “cracked” to allow air to bleed out.

Farmers and mechanics work alone more often than not, so it should come as no surprise that there’s an easier way to do things. Some mechanics wire up a remote starter switch on a cord so they can do both jobs at once, but if you can reach the air intake and the key, you can use a can of silicone spray to start your tractor. On my best small farm tractor, I can raise the hood, remove the air hose from the intake manifold and spray a little bit of silicone spray into the intake and crank the engine at the same time. The silicone spray acts like a temporary fuel source, which gets the engine running and if you give it a little spray every time the engine begins to stutter, you can keep it running until it purges the air from the fuel lines by itself. Use this spray very sparingly, overuse can result in damage to your engine, so use it at your own risk! Don’t use Ether spray of “starting fluid” instead of silicone spray, it’s not good to use on modern diesel engines and is more likely to damage the engine then help you get started. This bleeding method trick I picked up from Dave, a longtime Cummins® engine mechanic (thanks, Dave!).

Click Click, Click Click…

So why do I hate that sound? Over the last year, I’ve had algae bloom problems, a contaminated storage tank, gelled fuel, clogged fuel filters and an air filter clogged with chicken dust. I can’t count the times I’ve drained the battery trying to purge lines and restart the tractor. The most recent and hopefully last attempt at sorting out our problems has been draining the tractor’s tank, purging and replacing the fuel line from the tank to the filter, replacing both air filters (inner and outer), replacing the fuel filter again and adding fresh fuel to the tank straight from the gas station. This could have happened to any of the best small farm tractors, but unfortunately, it was mine. I hope all my lessons of necessity can someday help you answer the question; “Why won’t my tractor start?”

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