John Deere 7800 Problems (Reasons + Proven Solutions)

John Deere 7800 is one of the most popular farming tractors across the world. However, you should know about their common problems if you are thinking of buying one for your farm.

John Deere 7800 problems are centered on the engine. The most common engine problems include starting problems, low power generation, and overheating. Another problematic area of the tractor is its steering system. You may experience problems with the steering wheel and the front axle.

You will find reasons and solutions for all common problems of John Deere 7800 in this article. At the end of the article, you will be rewarded with some crucial maintenance tips too. 

John Deere 7800 Engine Problems

Problems Reason Solution
No Cranks, No Start Wrong fuel grade Change the fuel.
Incorrect fuel pump timing Adjust the Fuel Pump.
Cranks But No Start Faulty Starter Fix or Change the starter.
Clogged fuel filter or fuel line Clean fuel line and fuel filter.
Broken piston rings Replace piston rings.
Incorrect valve timing Adjust valve timing.
Engine Briefly Starts Substandard fuel Change the fuel.
Faulty ECM Fix or replace the ECM.
Faulty speed sensor  Fix or replace the speed sensor.
Poor Performance Clogged air filter Clean air filter. 
Faulty injectors Troubleshoot fuel injectors.
Diesel Knocks Carbon deposits  Clean the engine cabin.
Substandard fuel Change fuel.
Overheating Low coolant Fluid Top up coolant fluid.
Faulty temperature thermostat Fix or replace the thermostat.
Overload Reduce motor load.
Broken or misadjusted fan belt Adjust or replace the fan belt.
White Exhaust Gas Faulty piston rings Replace piston rings.
Poor quality fuel Change fuel.
Faulty fuel pump Fix or replace.

Problem 1: No Cranks, No Start

Does your John Deere 7800 crank when you turn the engine key without starting? It may happen due to:

  • Low-quality fuel
  • Faulty fuel pump
  • Mistiming of the fuel pump

If you use poor-quality fuel with the tractor, eventually, you may face this problem. So, be wise to choose the right fuelling station. Moreover, the fuel can get contaminated while the tractor is in operation. 

The engine needs an instant supply of fuel from the very beginning. So, if the fuel pump doesn’t supply fuel, there will be no cranks. And the engine won’t start either. 


Check the fuel quality of your tractor. Change it if the quality is not satisfactory. Remember to use #2 diesel fuel since heavy vehicles such as the John Deere 7800 need them. 

Examine the fuel pump for any faults. Check the timing of the fuel pump. In most cases starting problems come from the fuel pump timing. 

Problem 2: Engine Cranks But No Start

Some John Deere 7800 owners complain that the engine cranks but won’t start. The reasons for the problem are:

  • Faulty starter
  • Clogged fuel line
  • Clogged filters
  • Bad pistons

It can happen when the fuel line or the filter is clogged with dirt and foreign particles. An engine needs a fuel supply from the first moment you try to start it. If the supply is irregular for obstructions in the fuel line or filter, you only hear cranks.

The piston rings help to lower the engine heat. Besides, they help to keep up the good compression ratio inside engine cylinders. The engine cannot get started when there is poor compression in the combustion area. Hence, broken piston rings are also a reason for cranks without starting the engine.

Another important reason for the problem is wrong valve timing. If the timing is incorrect, a wrong amount of air enters the combustion area. 

Control input and output of the combustion cylinders. Furthermore, wrong valve timing also compromises the exhaustion procedure. As a result, the engine cannot create enough power to get started.


First, check the motor starter for any anomalies. You can check it using a multimeter as described in the following steps:

  • Attach the positive lead of the multimeter to the input terminal on the starter
  • Use alligator clips to ground the negative lead on a metal surface
  • Check if the meter shows 12 volts or not
  • Start the vehicle to see if the voltage reduces or not

If the voltage reading is not 12 volts or if it doesn’t reduce, the starter is bad. In that case, fix or replace the starter.

Engine Cranks But No Start

Check and troubleshoot the fuel line and the fuel filter. Generally, a thorough cleaning can clear all the dirt and other foreign particles. Examine the piston rings for any breakage and change them if necessary. 

A new set of piston rings for John Deere 7800 can cost you between $116 and $121. However, the installation cost could be $1000 and it varies depending on your region.

Diagnose the engine valve timing and correct any faults there. Fixing the problem may cost you $150 to $300.

Problem 3: Engine Briefly Starts

Sometimes, John Deere 7800 engines can stop functioning after a while you start them. This can happen for:

  • Adulterated fuel
  • Bad ECM
  • Faulty speed sensors

A common reason for this problem is the poor quality of fuel. If the engine cannot continue to produce enough energy, it may stop at some point. Another possible reason for this problem is a faulty ECM. 

The ECM controls all the procedures of the engine. If it goes bad, the ECM may stop the engine right after a while it starts. 

Another reason for brief engine starts can be a defective speed sensor. The ECM determines when to inject fuel into the engine by analyzing data from the speed sensor. If the sensor generates wrong data, the fuel supply will be irregular. As a result, the engine will stop due to a lack of the right fuel.


Check fuel quality and change if necessary. Check the ECM for any anomalies. The following video can be helpful: 

Problem 4: Poor Engine Performance

The John Deere 7800 farming tractor should produce around 170 horsepower of energy. The causes for an engine to produce less power are: 

  • Dirty air filter 
  • Faulty fuel injectors
  • Overload

The engine takes air and fuel as the input for combustion to create heat energy. It can’t intake the proper amount of air if the air filter is clogged with dirt. Moreover, the right amount of fuel will not flow in if the fuel injectors are faulty.


First, check the engine with a dynamometer to know if it is underperforming. After confirming the problem, clean the air filter to ensure proper airflow. Also, troubleshoot the fuel injectors to ensure proper fuel supply.

John Deere 7800 Poor Engine Performance
Source: Reddit

Problem 5: Knocking Sounds

Compared to other types of engines, diesel engines make louder knocking sounds. Causes for this problem include:

  • Accumulation of carbon deposits 
  • Incorrect air-fuel ratio
  • Low-quality fuel

So, when you hear loud knocking noises in your John Deere 7800 tractor, you should be alarmed. They may imply bigger problems.


Check your engine cabin for the accumulation of carbon deposits. Discharge the engine oil and clean the engine cabin properly. Top up the engine with good-quality oil.

Use good quality fuel to ensure proper and timely combustion in the engine cylinders. Check the fuel system and the pistons for any anomalies. 

Problem 6: Overheating

John Deere 7800 tractor engines can be overheated for:

  • Low coolant fluid
  • Faulty thermostat
  • Overload

The most common reason for a frequently hot engine is the lack of coolant fluid. The coolant fluids flow around the engine components to keep them cool. If the coolant fluid level is low, the engine gets hot.  

On average, the temperature of an engine cabin remains from 390°F to 480°F. The cooling system uses a thermostat.  When the temperature is higher than expected, a valve opens. 

The coolant fluid gets to flow when the valve is open. So, a malfunctioning thermostat disrupts the cooling system and makes the engine hot. 

An engine can also get overheated if you put more load on it than recommended. Sometimes, a faulty fan belt also makes the engine extra hot.


Top up the radiator with coolant fluid. Check and fix the temperature thermostat of the cooling system. Reduce load for the engine if necessary. Check if you need to adjust or replace the fan belt.

Problem 7: White Exhaust Gas

White exhaust gas indicates a fault in the cooling system or the combustion chamber. It implies that there is a leak in the combustion process. 

As a result of the leakage, the coolant fluid is getting into the combustion chamber. It may happen because of a crack in the cylinder head or bad piston rings. The white gas exhaust also happens for low fuel quality and irregular fuel supply. 


Check the piston and piston rings for any cracks. Make sure there is no leakage in the combustion chamber. Troubleshoot the fuel system and check the fuel quality. 

John Deere 7800 Steering Problems

Problems Reasons Solution
Wheel Turns Without Resistance Low level of hydraulic oil Top-up hydraulic oil.
Wear of the steering cylinder Fix or replace.
Broken steering pump Install a new pump.
Steering Doesn’t Work Leak in hydraulic connections Diagnose and fix.
Broken power pump steering Replace the steering pump.
Air bubbles in the hydraulic system Vacuum air from the hydraulic system.
Low level of hydraulic oil Top-up hydraulic oil.
Front Axle Cracking Defective gear Fix or replace gears.
Faulty ball Bearings  Change axle ball bearings.

Problem 1: Wheel Turns Without Resistance

The steering system of John Deere 7800 is hydraulic-based. You will experience no resistance in the wheel turning for these reasons:

  • Low hydraulic oil
  • Broken gearbox spring
  • Loose wheel bearings

You cannot drive the John Deere 7800 if the steering wheel lacks resistance. You should focus on the reasons mentioned above to resolve the issue. 


When you experience the steering wheel spinning without or with a little resistance. Take the following measures to solve the problem:

  • Top up the hydraulic oil 
  • Troubleshoot the steering gearbox. 
  • Check and fix any problem in the reaction spring, wheel bearing, or steering gear.
John Deere 7800 hydraulic fluid being topped up

Problem 2: Steering Not Working

Sometimes the steering of a John Deere 7800 may not work at all. Look for the following reasons when you face the problem:

  • Leakage in the hydraulic connections 
  • broken steering pump
  • air bubbles in the hydraulic system

Leakage in the hydraulic connections is a common reason for the problem. It may also happen from a broken steering pump.

You may also have some air bubbles in the hydraulic system to disrupt the steering. Low-level hydraulic oil and problems in the steering cylinder can also be the reason.


Check for any leakage in the hydraulic connections and fix them. Troubleshoot the steering pump and change it if necessary. You may follow the following steps to get rid of air bubbles from the hydraulic steering system:

  • Check the hydraulic oil level
  • Top up the oil if necessary
  • Attach a vacuum adapter or a hand vacuum pump with the cap of the oil reservoir
  • Pull 20 to 25 inches of vacuum while the engine is turned on idle
  • Turn the steering wheel back and forth at least ten times
  • Turn off the engine and check if the oil level is still okay
  • Repeat steps 1 to 6
  • Seal the oil reservoir with the cap.

Problem 3: Front Axle Cracking

Loud clunking or clicking noises in your front axle imply cracking. In that case, you may also have problems with braking and acceleration. Sometimes grease may leak from the front axle.

A defective gearbox can cause the front axle to crack. It may also happen when the ball bearings are not in a good shape. 


Troubleshoot the gearbox. Fix or replace gears if required. You will need to install new bearing balls at the front axle if they are damaged.

Maintenance Tips for Preventing John Deere 7800 Problems

You can cut the repair cost of a John Deere 7800 tractor with regular maintenance practices. Here I have compiled some tips to make the lifespan of your farming tractor longer:

  • Shade The Tractor: You should always keep the tractor in a shade in every weather condition. Regular contact with rain and snow can damage the exhaust system. Besides, chances of corrosion are also higher if you leave the tractor in an open space. 
  • Regularly Check Fluids: Your tractor needs different fluids in a certain volume. You must check and top up these fluids. Check and maintain the engine oil, coolant fluid, hydraulic oil, and battery electrolyte.
  • Ensure Right Tire Pressure: Know the right air pressure for each of the tires of your tractor. It will make the tractor operation smoother. At the same time, the tractor will have a longer life. 
  • Follow The User Manual: Always maintain the tractor as per the user manual. You should meticulously follow the maintenance schedule mentioned in the manual. Stick with the basic operating instructions from the manufacturer. 


Which is The Most Sought-After John Deere Tractor?

The 5105 is the most sought-after John Deere tractor. This farming tractor has a good record of being efficient in the field. The price of the tractor is also quite reasonable. Besides, John Deere 5105 is also popular for fuel efficiency and great looks.

How Much Horsepower Does A John Deere 7800 Have?

The manufacturer claims that the John Deere 7800 has a horsepower of 170. However, an independent test has found a maximum of 158.97 horsepower at the PTO or power shaft of the tractor. Tests found 146.73 horsepower in the tractor at the rated engine speed.

What Is The Lifespan Of A John Deere Tractor?

On average, the lifespan of a John Deere Tractor can be between 4,000 to 10,000 operation hours. The exact lifespan depends on the work environment and maintenance.

Parting Words

This article aimed to cover all the common John Deere 7800 problems. Did I miss anything? Do you want to know the solution for problems of any other tractor type? 

Maybe you can help me make this article better. Share your thoughts about the write-up by leaving a message below. Or you can email us too. Till next time!

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