John Deere Ignition Coil Problems – What To Do And How To Catch It?

The ignition coil, or the starter coil as it’s called most commonly, is a vital part of any vehicle. As the name suggests, it helps kickstart the engine. The basic gist of it is that it transfers the battery voltage to the spark plug, which in turn ignites the engine.

Now, just like any other components in a lawnmower, the ignition coil can fail, even on high-end models from a respected brand like John Deere. And when it does fail, whether due to natural wearing or neglect from the owner, it can present itself in all sorts of weird issues in your lawnmower.

But if you have little experience with the workings of a lawnmower, you might not even notice that the ignition coil in your vehicle is failing. And without identifying that the ignition coil is having issues, you will not be able to fix your mower. So, there are two steps here, identifying the issue and fixing it.

In this article, I will try to help you out with both by giving you a complete guideline on catching ignition coil problems in your John Deere lawnmower and helping you fix it. So, without further ado, let us get started.

Signs Of A Bad Ignition Coil In Your Lawnmower

Now, before I take you further, let me make one thing clear – you don’t have to diagnose the issue at all if you are not comfortable with tinkering around with the lawnmower. If you want, you can simply take it to a garage and get it checked by professionals.

But that would, of course, cost you a fair bit of money. Personally, I think it’s a good idea to be able to service the basic issues of your mower by yourself. This would not only help you save money in the long run but will also help you learn how to better take care of your machine.

With that said, let’s move on with the common signs that the ignition coil in your John Deere lawnmower is failing:

1. Engine Cranks But Won’t Start

One of the earliest signs that your ignition coil is about to die is that the engine will crank, but the mower will refuse to boot up. Of course, other issues can also cause this symptom in a John Deere lawnmower, so make sure you rule them out first.

An alternative solution to this symptom is to clean the filters and check all the connections and wiring in the mower. You should also inspect the starter switch, as that might be the culprit here. Lastly, take a look at the battery and see if it’s fully charged. If none of these are causing the problem, then the ignition coil is bad.

2. Engine Overheats

If you suddenly notice that the mower’s engine is running too hot, then you probably have a faulty ignition coil. A malfunctioning or poorly performing ignition coil can put a lot of stress on the engine, causing it to push itself. This, in turn, causes the engine to overheat.

But before you take the engine overheat as a sign of ignition coil, check the carburetor and fuel level in the oil tank. A dirty, clogged-up carburetor can also cause the engine to overheat.

If that’s the case, cleaning the carburetor should fix the issue. And if the fuel in the tank is fresh and topped off, then fuel is not causing this problem either.

3. Sudden Engine Shut Down

Imagine you are mowing your front lawn in your trusty John Deere tractor one fine morning, and all of a sudden, the mower shuts down. If this seems familiar, then you probably have a faulty ignition coil. In fact, the mower might even start again when you turn it on, but it will keep shutting down until you replace the starter.

Now, sudden loss of engine power can also be caused due to a malfunctioning engine or faulty spark plug. And while engine issues can be tricky to diagnose, you can easily check if the spark plugs are the culprit. Simply buy and replace the spark plugs in your mower and see if that fixes the issue. If not, then the ignition coil is your next best bet.

4. Bad Fuel Efficiency

Another sign that you might have a failing ignition coil in your lawnmower is that you see your mower consuming too much fuel all of a sudden. John Deere lawnmowers are usually extremely fuel-efficient, and if it starts chugging down fuel like crazy, it’s a safe bet that the ignition coil is acting up.

But then again, you need to make sure you are using high-quality gasoline in your lawnmower instead of those cheap ones with alcohol additives. Despite the quality of your lawnmower, cheap gasoline burns up way too fast, giving you less mileage per refuel. But if your mower is still consuming too much gas even when you are using high-quality gasoline, then it’s probably a sign of a faulty ignition coil.

How To Check Faulty Ignition Coil?

Thankfully, testing the ignition coil in your John Deere mower is pretty simple. You only need a multimeter and a copy of the service manual to do this.

Of course, the first step is to take out the ignition coil itself, which you should be able to do by following the instructions in the manual.

Since all John Deere lawnmowers are different, you have to figure this step out for yourself. Once you take out the ignition coil, here are the steps to check it:

• Switch the multimeter to the 20k resistance mode for measurement.
• Look up the ignition coil’s resistance and tolerance value chart in your instruction manual. If you don’t have a manual, you can download one online.
• Take one part of the multimeter and put it on the coil’s base while inserting the other end into the high-tension lead’s spark plug cap.
• Note the resistance value and compare it to the range of values in the manual.
• Now take the end of the multimeter that was on the spark plug cap and switch it to the terminal in the coil’s kill wire.
• Note the resistance value in the multimeter and check it in the user manual. The trick is to look for specific values of resistance in the table when the multimeter is connected to specific points in the coil.
• Lastly, place one end in the kill wire terminal and insert the other end in the spark plug cap.
• Similar to the previous steps, note down the resistance value.
• Now, if the values that you get from the multimeter are not present in the table or if the multimeter gives no values at all, this means the ignition coil is malfunctioning. At that point, your only option is to replace it.

How To Replace The Ignition Coil In Your John Deere Lawnmower?

Replacing the ignition coil is a lot easier than identifying the problem. If you have already checked the ignition coil by yourself, then buying and installing a new coil should not be that difficult.

The first step here is to get a coil that is compatible with the engine in your John Deere lawnmower. You can, of course, try to get in touch with the manufacturer, and they should send you a replacement coil. But if you can’t contact them or simply don’t want to, then look up the engine parts number and use it to find a compatible coil.

Before installing the ignition coil, make sure you put the spark plug back in place. Then connect the wires in the spark plug to the terminals in the ignition coil. Double-check to make sure the wires are connected properly according to the user’s manual.

When putting the ignition coil back in its place, make sure the distance between the coil and the flywheel magnet is exactly 10 points. Use a gauge and measure the distance properly.

Finally, use a screwdriver to attach the screws to the ignition coil. That’s about all there’s to it. After that, you can assemble the mower and test out the new ignition coil.

The Bottom Line

Ignition coil issues in your lawnmower can present themselves in weird ways. And as a new user, it’s not surprising if you can’t pinpoint an issue in the ignition coil.

Now, John Deere lawnmowers are well-made machines. And a new unit should not have a faulty ignition coil anytime soon if you take care of it. But once you have had the mower for a while and used it for a lot of projects, a failing ignition coil is a real possibility that you might have to deal with.

I hope my article on John Deere ignition coil problems could help you figure out any issues in the ignition coil and fix it with little to no hassle. Good luck!