6 Most Common John Deere 790 Problems and How to Fix Them

Although the 790 John Deere tractor has not been in production since 2007, it is still a functional compact tractor to have around. As with other tractors, expect a few issues with this old JD model. The most common John Deere 790 problems are difficulty raising the 3-point hitch, heavy steering, the engine refusing to start, difficulty shifting gears, knocking engine noises, and the tractor leaning on one side.

Fortunately, you can resolve most of these issues by replacing worn-out parts, adjusting misaligned components, and regular maintenance. Here’s how you tackle each John Deere 790 problem.

Engine Won’t Start

The engine is your tractor’s powerhouse. And when it doesn’t start, it could point to a few issues you must address. First, start with the simple reasons like insufficient or poor quality fuel. The only solution for poor-quality fuel is replacing it with the recommended fuel for your tractor.

If your tank has fuel but still won’t start, it could mean that the fuel isn’t reaching the engine due to a clogged fuel filter or fuel injector. Start by removing and cleaning the fuel filter. If the problem persists, check the fuel injector for signs of clogging. Remove any debris from the injector using a fuel injector cleaner.

In some cases, the engine does not have any problem except for influences from the external environment. For instance, if you leave your JD 790 tractor out on a winter night, it’s likely to have problems starting the following morning due to the cold. In this case, placing the tractor in a warm place for some time should help start the engine.

Difficulty Shifting Gears

John Deere 790 problems with the transmission system can manifest as difficulty shifting gears. This problem occurs due to several reasons.

Wear or rust in the gear shift linkage is one of the top causes. You can resolve the issue by replacing the worn-out components and lubricating the gear shift linkage to prevent corrosion.

It might also be hard to shift gears due to a faulty or maladjusted clutch system. Check whether the clutch is in the correct position. While at it, inspect for any signs of wear or tear and replace the clutch if worn out.

Low transmission fluid levels could also contribute to problems with shifting gears. Therefore, check the fluid level and refill if necessary. 

Difficulty Raising the 3-Point Hitch

You might experience difficulties raising the 3-point hitch on your John Deere tractor for several reasons. The problem could be with the hydraulic fluid. Check the levels of your John Deere 790 hydraulic fluid to ensure it’s adequate. If not, refill the reservoir to the appropriate level.

In some cases, you might have adequate hydraulic fluid, but it cannot reach the 3-point hitch due to a defective control valve. You can fix the problem by repairing or replacing the control valve.

It might also be difficult to raise the hitch when the hydraulic lines are blocked or damaged. You must either remove the clogs in the system or replace the damaged components to restore your tractor’s efficiency.

Heavy Steering

Steering system issues are among the most common John Deere 790 problems. In most cases, transmission problems are behind the issue. You may experience heavy steering due to the following reasons:

  • Air in the steering system
  • Clogs in the steering filter
  • Low fluid levels
  • Improper tire pressure
  • Worn-out components

Air in the steering system interferes with its performance, making it hard to steer the vehicle. You’ll know trapped air is causing the problem due to problems turning the steering wheel, especially at low speeds, and a groaning noise when steering. The steering might also feel loose, creating issues with controlling the tractor.

Another reason for heavy steering is clogging in the steering filter. Clean the steering filter to clear any debris. Next, refill the steering fluid to ensure the steering system has the correct hydraulic pressure for smoother steering.

The tire pressure could also create steering issues in your John Deere 790 tractor. Uneven tire pressure creates imbalanced handling and resistance, which makes steering difficult. It can also cause the tractor to lean onto one side, making it even harder to control. If you’re experiencing this issue, check all tires to ensure they have the recommended pressure.

The Tractor Pulls to the Left or Right

When your tractor starts pulling to the left or right, it could be a problem with the steering unit, wear and tear, or incorrect adjustments. It could also be a sign of John Deere 790 front axle problems.

Your tractor will also lean to one side if the wheels have uneven tire pressure. Check the tires and adjust them to the recommended pressure.

You might also notice the leaning if you’re carrying an uneven load. You can resolve the problem by balancing any attachments or load.

Wear and tear of the steering unit and suspension components can also contribute to the tractor’s leaning to one side. When worn out, the suspension cannot support your tractor’s weight properly, and the steering column cannot guide the tractor as expected. Check the two systems for wear or tear and replace the damaged parts.

Knocking Noises in the Engine  

Some John Deere 790 problems affect the engine. Normally, the tractor engine produces some noise, but you should take notice when that noise shows up as knocking sounds.

Knocking noises in the engine indicate several possible issues. Low oil pressure is one of the primary reasons. Low oil pressure may be due to low engine oil levels, oil pump failure, clogged oil passages, and worn engine bearings.

Low oil pressure is a serious issue that you must address promptly to avoid damaging the engine. Start by refilling fluid levels and checking for worn-out or damaged components. Repair and replace any damaged parts as necessary.

If you have used your engine for a significant time, piston wear could be the reason behind the knocking noises. Piston wear comes from friction and poor maintenance practices.

Replace worn-out pistons as soon as possible to prevent additional damage to the engine. You can also prolong their life cycle by having a consistent maintenance schedule to prevent unnecessary damage or wear.

Regularly Maintain Your JD 790 Tractor

The 790 John Deere might be an older model, but it can still complete many tasks around your farm, lawn, or ranch. It is a reliable model which can go a long way with proper maintenance. 

Part of the maintenance involves resolving problems as soon as you notice them. Hopefully, this article can help you troubleshoot your tractor the next time there’s an issue.