Stihl Chainsaw Coil Troubleshooting (MS880 Ignition Fix Tips)

Living in the Pacific Northwest, where the air hangs heavy with the scent of damp earth and towering Douglas firs, I’ve learned that understanding your chainsaw is as crucial as knowing the terrain. The climate here demands resilience – not just from us, but from our tools as well. A sputtering chainsaw in the middle of felling a massive tree isn’t just an inconvenience; it can be downright dangerous. That’s why I’m diving deep into a critical issue for many of us who rely on the Stihl MS880: ignition coil troubleshooting. This powerhouse saw is a workhorse, but like any machine, it can have its quirks. Let’s get into some troubleshooting tips to keep your MS880 roaring.

Stihl Chainsaw Coil Troubleshooting (MS880 Ignition Fix Tips)

The Stihl MS880 is a beast of a chainsaw, designed for the toughest jobs. But even the toughest machines can falter. One of the most common culprits behind a non-starting or poorly running MS880 is the ignition coil. The ignition coil is a critical component that generates the high-voltage spark needed to ignite the fuel-air mixture in the engine. When it fails, your saw is dead in the water.

Understanding the Ignition System

Before we start wrenching, it’s crucial to understand how the ignition system works on an MS880. The system is relatively straightforward:

Flywheel: As the engine turns, the flywheel spins. Magnets embedded in the flywheel pass by the ignition coil.
Ignition Coil: The magnets passing the coil induce a voltage in the coil’s primary winding. This voltage is then amplified by the coil’s secondary winding.
Spark Plug: The high-voltage electricity is sent to the spark plug, creating a spark that ignites the air-fuel mixture in the cylinder.
Ground: The circuit is completed through the engine block, providing a ground path.

A failure in any of these components can lead to ignition problems. However, the ignition coil itself is often the prime suspect.

Symptoms of a Faulty Ignition Coil

Recognizing the symptoms of a failing ignition coil is the first step in troubleshooting. Here are some common indicators:

No Spark: This is the most obvious symptom. The engine simply won’t start because there’s no spark to ignite the fuel.
Weak Spark: The engine might start, but it runs poorly, sputters, or lacks power. A weak spark might not be strong enough to consistently ignite the fuel.
Intermittent Starting: The saw starts sometimes but not others. This can be due to a coil that is failing intermittently.
Engine Stalling: The engine starts and runs for a short period, then stalls. This can happen when the coil overheats and fails.
Difficult Starting When Hot: The saw starts easily when cold but is hard to start when hot. This is another sign of a coil that’s breaking down under heat.

Preliminary Checks Before Coil Diagnosis

Before you condemn the ignition coil, it’s essential to rule out other potential causes of starting problems. I’ve seen many folks replace a perfectly good coil only to find the problem was something else entirely.

Spark Plug: The spark plug is the easiest and cheapest component to check. Remove the spark plug and inspect it. Look for:
- Cracks or Damage: Any visible damage to the spark plug insulator.
- Fouling: Excessive carbon buildup, oil, or fuel on the electrode.
- Gap: The spark plug gap should be within the manufacturer’s specifications (usually around 0.5mm or 0.020 inches for the MS880). Use a spark plug gap tool to verify and adjust if necessary.
- Testing: Connect the spark plug to the spark plug wire, ground the spark plug body against the engine, and pull the starter rope. You should see a strong, blue spark jump across the electrode gap. If the spark is weak, yellow, or nonexistent, replace the spark plug.
Fuel System: A lean or rich fuel mixture can cause starting problems that mimic ignition issues.
- Fuel Filter: A clogged fuel filter restricts fuel flow. Replace the fuel filter if it’s dirty.
- Carburetor: A dirty or improperly adjusted carburetor can cause starting and running problems. Clean the carburetor and ensure it’s properly adjusted. Consider a carburetor rebuild kit if the carburetor is heavily soiled or has damaged components.
- Fuel Line: Check the fuel line for cracks, leaks, or kinks that could restrict fuel flow.
- Fuel Quality: Ensure you’re using fresh, high-quality fuel mixed with the correct ratio of two-stroke oil. Old or improperly mixed fuel can cause starting problems.
Air Filter: A clogged air filter restricts airflow to the engine, leading to a rich fuel mixture and starting problems. Clean or replace the air filter.
Compression: Low compression makes starting difficult. Use a compression tester to check the engine’s compression. The MS880 should have a compression reading of around 120-150 PSI. If the compression is significantly lower, you may have worn piston rings, a damaged cylinder, or leaky valves.

Testing the Ignition Coil

Once you’ve ruled out other potential causes, it’s time to test the ignition coil. There are two primary methods: the spark test and the multimeter test.

Spark Test

The spark test is a simple visual inspection to see if the coil is producing a spark.

Disconnect the Spark Plug: Remove the spark plug from the cylinder head.
Connect the Spark Plug to the Wire: Reconnect the spark plug to the spark plug wire.
Ground the Spark Plug: Hold the spark plug against the engine block, ensuring good metal-to-metal contact. Use insulated pliers or gloves to avoid getting shocked.
Pull the Starter Rope: Pull the starter rope firmly and observe the spark plug.

Interpreting the Results:

Strong, Blue Spark: A strong, blue spark indicates the ignition coil is likely functioning correctly. The problem may lie elsewhere.
Weak, Yellow Spark: A weak, yellow spark suggests the ignition coil is weak or failing.
No Spark: No spark at all indicates the ignition coil is likely faulty.

Safety Note: Be extremely careful when performing the spark test. The high-voltage electricity can give you a painful shock. Always use insulated pliers or gloves, and ensure you have a good ground connection.

Multimeter Test

A multimeter provides a more precise way to test the ignition coil. This test involves measuring the resistance of the coil’s primary and secondary windings.

Tools Needed:

Multimeter
Service Manual (for resistance specifications)

Procedure:

Disconnect the Ignition Coil: Disconnect the ignition coil from the spark plug wire and the wiring harness.
Set the Multimeter: Set the multimeter to the ohms (Ω) setting. You may need to select a specific range, depending on your multimeter.
Measure Primary Resistance: Touch the multimeter probes to the primary terminals of the ignition coil. The primary terminals are typically the two smaller terminals where the wiring harness connects. Record the resistance reading. Compare this reading to the specifications in the service manual.
Measure Secondary Resistance: Touch one multimeter probe to the spark plug wire terminal and the other probe to the engine ground terminal on the coil. Record the resistance reading. Compare this reading to the specifications in the service manual.

Interpreting the Results:

Readings Within Specifications: If both the primary and secondary resistance readings are within the specifications in the service manual, the ignition coil is likely good.
Readings Outside Specifications: If either the primary or secondary resistance reading is outside the specifications, the ignition coil is likely faulty and needs to be replaced.
Open Circuit: An open circuit (infinite resistance) indicates a broken winding inside the coil.
Short Circuit: A short circuit (very low resistance) indicates a shorted winding inside the coil.

Example Data:

While exact values vary by manufacturer, here are some typical resistance ranges for a small engine ignition coil:

Primary Resistance: 0.5 – 5 ohms
Secondary Resistance: 2,000 – 15,000 ohms

Always consult the service manual for your specific Stihl MS880 model for accurate resistance specifications.

Ignition Coil Replacement

If your testing indicates a faulty ignition coil, the next step is replacement.

Tools Needed:

New Ignition Coil (matching the Stihl MS880 model)
Screwdrivers
Socket Set
Torque Wrench (optional, but recommended)

Procedure:

Disconnect the Spark Plug Wire: Remove the spark plug wire from the spark plug.
Remove the Engine Cover: Remove the engine cover to access the ignition coil. The exact procedure varies depending on the MS880 model, but typically involves removing several screws or bolts.
Disconnect the Wiring Harness: Disconnect the wiring harness from the ignition coil.
Remove the Old Ignition Coil: Remove the screws or bolts that hold the ignition coil in place. Carefully remove the old ignition coil.
Install the New Ignition Coil: Install the new ignition coil in the same location as the old one. Tighten the screws or bolts to the specified torque (if available in the service manual).
Connect the Wiring Harness: Connect the wiring harness to the new ignition coil. Ensure the connections are secure.
Reinstall the Engine Cover: Reinstall the engine cover and secure it with the screws or bolts.
Connect the Spark Plug Wire: Reconnect the spark plug wire to the spark plug.
Test the Engine: Start the engine and verify that it runs properly.

Important Considerations:

Air Gap: The air gap between the ignition coil and the flywheel is crucial for proper ignition. The air gap is the small space between the ignition coil and the flywheel magnets. If the air gap is too large or too small, the coil won’t generate enough voltage to produce a spark. The correct air gap for the MS880 is typically around 0.3mm (0.012 inches). Use a business card or a feeler gauge to set the air gap correctly when installing the new coil.
OEM vs. Aftermarket: When replacing the ignition coil, you have the option of using an original equipment manufacturer (OEM) part or an aftermarket part. OEM parts are typically more expensive but are generally considered to be of higher quality and more reliable. Aftermarket parts are less expensive but may not be as durable or perform as well as OEM parts. I always recommend using OEM parts when possible, especially for critical components like the ignition coil. I’ve had too many experiences with aftermarket parts failing prematurely.
Torque Specifications: Use a torque wrench to tighten the screws or bolts that hold the ignition coil in place. Overtightening can damage the coil or the engine block. Consult the service manual for the correct torque specifications.

Advanced Troubleshooting Tips

Sometimes, even after replacing the ignition coil, starting problems persist. Here are some advanced troubleshooting tips to consider:

Wiring Issues: Inspect the wiring harness for any damaged, frayed, or corroded wires. Repair or replace any damaged wiring. Use a multimeter to check the continuity of the wires.
Kill Switch: The kill switch is designed to ground the ignition system and stop the engine. If the kill switch is faulty or shorted, it can prevent the engine from starting. Disconnect the kill switch and see if the engine starts. If it does, replace the kill switch.
Flywheel Key: The flywheel key is a small metal piece that aligns the flywheel with the crankshaft. If the flywheel key is sheared or damaged, the timing will be off, and the engine won’t start. Inspect the flywheel key for damage.
Ignition Module: Some MS880 models have an ignition module in addition to the ignition coil. The ignition module controls the timing and duration of the spark. If the ignition module is faulty, it can cause starting problems. Test the ignition module according to the service manual.
Electronic Ignition System: Some newer MS880 models have an electronic ignition system. These systems are more complex and require specialized diagnostic tools. If you suspect a problem with the electronic ignition system, consult a qualified technician.

Case Studies and Real-World Examples

I’ve seen countless scenarios where a seemingly simple ignition problem turned into a complex diagnostic challenge. Here are a couple of examples:

Case Study 1: The Intermittent Stall

A local logger brought in his MS880 complaining of intermittent stalling. The saw would start and run fine for a while, then suddenly stall. He had already replaced the spark plug and cleaned the carburetor, but the problem persisted. I performed a spark test, and the spark appeared to be strong. However, after running the saw for about 15 minutes, the spark became weak and erratic. A multimeter test confirmed that the ignition coil was breaking down under heat. Replacing the ignition coil solved the problem.

Case Study 2: The No-Start Mystery

A homeowner brought in his MS880, which wouldn’t start at all. He had tried everything he could think of, but the saw remained stubbornly silent. I started with the basics: spark plug, fuel system, and air filter. Everything checked out. I then performed a spark test and found no spark at all. A multimeter test confirmed that the ignition coil was faulty. However, after replacing the ignition coil, the saw still wouldn’t start. I then inspected the wiring harness and found a corroded wire near the kill switch. Repairing the wire solved the problem.

These case studies highlight the importance of thorough troubleshooting and attention to detail. Don’t assume that the ignition coil is the only possible cause of starting problems. Always check the other components of the ignition system and the engine.

Maintaining Your Ignition System

Preventive maintenance is key to keeping your MS880 running smoothly and avoiding ignition problems.

Spark Plug Replacement: Replace the spark plug regularly, typically every 50-100 hours of use.
Air Filter Cleaning: Clean the air filter regularly, especially in dusty conditions.
Fuel System Maintenance: Use fresh, high-quality fuel mixed with the correct ratio of two-stroke oil. Drain the fuel tank before storing the saw for extended periods. Clean or replace the fuel filter as needed.
Ignition Coil Inspection: Inspect the ignition coil for any signs of damage or corrosion. Clean the coil and ensure the wiring connections are secure.
Storage: Store the saw in a dry, protected area. Remove the spark plug and spray a small amount of fogging oil into the cylinder to prevent corrosion.

The Bottom Line

Troubleshooting the ignition system on a Stihl MS880 can seem daunting, but with a systematic approach and a basic understanding of how the system works, you can diagnose and repair most problems yourself. Remember to start with the basics, rule out other potential causes, and use the appropriate testing methods. And always prioritize safety when working with high-voltage electricity.

By following these tips, you can keep your MS880 running strong and tackle even the toughest jobs with confidence. After all, a reliable chainsaw is more than just a tool; it’s a partner in getting the job done.

Stihl Chainsaw Coil Troubleshooting (MS880 Ignition Fix Tips)