Stihl 020 AVP Ignition Problems (Troubleshooting)
On an 020 AVP that will not start, check the stop switch, wiring, spark plug, and ignition spark before buying parts. Test spark with an enclosed tester and the switch set to RUN. If spark is present, stop blaming the ignition and check fuel, compression, and flooding. Use the correct manual for all model-specific settings.
“Measure twice, cut once.” The same idea saves time on a no-start saw: test one thing at a time, and do not replace an ignition module just because the engine stayed quiet after 30 pulls.
The 020 AVP is an older saw in roughly the 35 cm³ class, but parts and settings can vary by model version and installed components. First confirm the model identification and serial number. Then use the matching STIHL manual or service information before setting the plug gap, module clearance, torque, or carburetor.
Prepare the saw and work area
This first check protects you from shock, fire, and accidental chain movement while helping rule out simple faults. Let the saw cool, switch it off, and work outdoors or in a well-ventilated area. Keep fuel and vapors away from sparks, flames, and hot surfaces.
Set the saw on stable ground and engage the chain brake. Remove the spark-plug boot before inspecting the plug or ignition parts. Do not pull the starter with an exposed high-voltage lead near fuel vapors.
Check that the saw is identified as an 020 AVP, not just an older STIHL with a similar appearance. If the serial-number manual is not available, ask STIHL or a qualified dealer for the correct specifications. Do not assume a modern fuel ratio or generic plug gap applies.
Look over the saw before testing:
- Check for fuel leaks, damaged wiring, loose connections, and a cracked plug boot.
- Look for damage around the flywheel and ignition module. Do not remove or alter parts unless you have the right tools and service data.
- Confirm the chain brake works and the chain is correctly fitted. Bar length alone does not confirm bar-and-chain compatibility; check mount, pitch, gauge, and drive-link count.
- Keep hands and clothing away from the chain and moving parts during all starting tests.
Next step: If you find a leak, damaged insulation, or a safety fault, fix that before trying to start the saw.
Check the stop switch, wiring, and spark plug
A stop-switch wire can prevent ignition by grounding the circuit. A dirty connection, damaged lead, loose boot, or incorrect plug can also cause weak or missing spark. Inspect these simple items first, because they are easier to check than the ignition module.
With the plug boot removed, inspect the plug for cracks, heavy carbon, oil, or fuel. Check that the boot fits firmly and that the visible wires and connectors are intact. A wet plug after many start attempts often means the engine is flooded; by itself, it does not prove the ignition module has failed.
Use the plug type listed for the saw’s serial-number version. Check its electrode gap against the correct manual specification, not a value from another model or a generic chart. Replace a cracked, carbon-tracked, oil-fouled, or incorrect plug with the specified type.
Inspect the stop-switch circuit and its connections for damage or a wire that may be grounding against the engine. Do not bypass or disconnect the switch to test or operate the saw. You need a working way to stop the engine.
Next step: If the switch and visible wiring look sound, test spark with a proper enclosed tester.
Test for spark safely
An enclosed inline spark tester shows whether ignition is reaching the plug lead during cranking. It is safer than holding a loose plug against the cylinder, and it helps you separate a spark problem from fuel or compression trouble.
- Switch off the saw and let it cool. Remove the plug boot, then connect the tester as its instructions describe.
- Refit the plug boot securely. Keep the tester and connections clear of fuel, vapors, and moving parts.
- Set the stop switch to RUN and pull the starter. Watch the tester for a spark.
- If spark appears, move the switch to STOP and repeat only as directed by the tester instructions. Spark should be interrupted. Do not run the saw with a disabled stop switch.
- If the result changes when you gently move a wire or connector, suspect a loose or damaged connection. Do not touch a bare lead while cranking.
| Tester result | What it points to | What to check next |
|---|---|---|
| No spark in RUN | Switch circuit, wiring, plug lead, module, or flywheel issue | Inspect connections and stop-switch wire; then test parts by the correct service procedure |
| Spark comes and goes | Loose, damaged, or shorting connection; possible component fault | Inspect the harness and connections while testing safely |
| Spark in RUN, none in STOP | Stop switch may be interrupting spark as intended | Continue with plug, fuel, compression, and other no-start checks |
| Spark remains in STOP | Stop-switch circuit may not be grounding correctly | Repair the switch circuit before operation |
A visible spark does not prove the ignition works correctly under every condition. If the saw still will not run, do not keep replacing ignition parts at random. Move on to fuel and compression checks.
If there is no spark
No spark does not name the failed part. Start with the stop-switch wire and connections, because a grounded or damaged wire can suppress spark even when the module itself is not the cause.
With the saw off and cool, inspect the switch, wiring, plug boot, and visible ignition lead. Repair damaged insulation or loose connections with the correct parts. Do not use a running test with the stop switch bypassed.
If the wiring and switch check out, the ignition module and flywheel need testing against the correct service data. The module-to-flywheel air gap, fastener torque, and setup method depend on the installed parts and manual. Do not guess a clearance or torque value, and do not force the flywheel or module into a new position without following the service procedure.
A damaged flywheel or module may need replacement, but confirm the fault first. If you lack the tools or service information for those checks, a repair shop can test the ignition system without requiring you to buy parts on a hunch.
Next step: Restore the stop-switch function, then repeat the enclosed-tester check. If spark is steady in RUN and stops in STOP, shift to fuel and engine checks.
If spark is present but the saw will not start
Spark is only one part of combustion. A wet plug, stale fuel, a blocked exhaust, poor compression, or a fuel-delivery problem can all leave a saw unable to start even when the tester shows spark.
Check that the fuel is fresh and mixed at the ratio specified in the correct 020 AVP manual for the oil being used. Do not assume 50:1 on this vintage saw. If you cannot find the manual, get STIHL or dealer guidance before running it.
Use the manual’s cold- or warm-start procedure. If repeated pulls have left the plug wet, follow the manual’s flooding-clearing steps instead of continuing to pull with the choke set. Do not use starting fluid or other unapproved methods.
If fuel and starting procedure are correct, check the fuel system, carburetor metering, muffler or spark arrestor, and compression. A compression test requires the right gauge and a model-appropriate method; without the service limit, a number cannot reliably tell you whether the engine is within specification. If compression is low or the crankcase may not seal, seek a proper test before adjusting the carburetor.
| Finding | Likely direction | Avoid |
|---|---|---|
| Plug is wet after repeated pulls | Flooding or excess fuel during starting | Replacing the ignition module based only on a wet plug |
| Plug stays dry after proper starting steps | Fuel may not be reaching the cylinder | Random carburetor screw changes |
| Spark is steady but no start | Fuel, compression, exhaust, or starting procedure | Assuming spark alone proves the whole ignition system is sound |
| Engine starts but will not idle safely | Idle, clutch, or related fault | Cutting until the chain stays still at idle |
Two useful diagnostic examples
These are diagnostic patterns, not reports of a specific saw. They show why a test result matters more than a guess based on symptoms alone.
Example 1: No spark, but the tester result changes when the harness moves.
That points first to a loose connection or damaged wire. Inspect and repair the circuit, then retest with the stop switch working. Replacing the module before checking the harness could waste money and leave the fault in place.
Example 2: Steady spark, wet plug, and no start after many pulls.
The wet plug makes flooding a reasonable possibility, but it does not prove the cause. Follow the manual’s clearing procedure, use the correct starting steps, and check fuel condition. If the saw still will not start, continue to fuel-delivery, exhaust, and compression checks.
Verify the repair before cutting
A successful start is not the end of the test. Refit the plug and boot, use the prescribed starting procedure, and start outdoors on stable ground with the chain brake engaged. Confirm the saw responds cleanly and shuts off when you use the stop switch.
If the saw starts but the chain moves at idle, stop it immediately. Do not lower the idle setting until the engine stalls as a workaround. The saw needs diagnosis of the idle or clutch fault, and the chain must remain stationary at idle before use.
Before cutting, check that the chain brake works and that the bar and chain match the sprocket and saw. Use the chain maker’s limits and the saw’s manual for the setup. Do not tune maximum engine speed by ear; use the proper service data and measuring equipment.
After the test, shut down and let the saw cool. Check for fuel leaks, loose parts, and debris around the cooling and starter areas. For storage, follow the manual’s fuel directions. Old fuel can create no-start symptoms that resemble ignition trouble.
Key takeaway: A safe repair confirms three things: dependable spark in RUN, spark interruption in STOP, and a saw that starts, idles without chain movement, and shuts off normally.
Frequently asked questions
Why does my 020 AVP have no spark?
Possible causes include a stop-switch fault, damaged or grounded wiring, a poor connection, a plug or lead fault, or an ignition-module or flywheel problem. Test in that order rather than replacing parts at random.
Can a bad stop switch prevent the saw from starting?
Yes. If its wire or circuit grounds the ignition when the switch is in RUN, the engine may have no spark. Inspect and test the circuit, but do not bypass it.
Should I test spark with the plug held against the cylinder?
Use an enclosed inline spark tester instead. Do not hold a plug or bare ignition lead by hand during cranking.
Does a wet spark plug mean the ignition module is bad?
No. A wet plug after repeated attempts may indicate flooding. It does not prove an ignition fault.
What spark plug gap should I use?
Use the gap specified for the correct plug and serial-number version in the saw’s manual. Do not rely on a generic gap value.
Can I use a 50:1 fuel mix?
Do not assume that ratio applies. Check the correct manual for the saw and oil type, or ask STIHL or a dealer before running it.
What should I check if spark is present?
Check the starting procedure, fuel condition and delivery, carburetor, exhaust, compression, and crankcase sealing as needed. Spark alone does not confirm the engine is ready to run.
Why does the chain move when the saw idles?
Treat that as a safety fault. Stop the engine and diagnose the idle or clutch problem before cutting; the chain must stay still at idle.
Can I set the ignition air gap by eye?
No. Use the service-manual value and procedure for the installed ignition parts. A guessed gap can lead to poor operation or damage.
When should I take the saw to a shop?
Get qualified help if you cannot test the module or flywheel safely, lack the correct service data, or suspect low compression or a crankcase leak. A focused diagnosis is better than buying unverified parts.
(This article was written by one of our staff writers, Robert Callahan. Visit our Meet the Team page.)
