husqvarna 55 chain saw

mechanic · Jun 24, 2019

Won't start. When I use the spark tester I can see spark as I pull the rope but when I stick the spark plug in I don't see anything. The plug gets wet when I try to start but no spark to the plug. That same plug will run my weed eater. What I don't understand is why does the spark tester show spark but the plug shows nothing. I'm almost ready to buy a coil and give it a try Any ideas?

RNeumann · Jun 24, 2019

The coil and wire shouldn’t have more than a few ohms of resistance. Test that before you get a new coil. Also verify the on/off switch is making good contact- that’s one of the more common “no spark” causes.

RandyT · Jun 25, 2019

Are we sure that the flywheel hasn't slipped and throwing the timing off. And have you tried a new plug in the saw. They can do weird things sometimes. Is there a possibility that the carb is dumping too much fuel in causing a flooding issue.

John_Mc · Jun 25, 2019

RNeumann said:
The coil and wire shouldn’t have more than a few ohms of resistance. Test that before you get a new coil. Also verify the on/off switch is making good contact- that’s one of the more common “no spark” causes.

Actually, on a chainsaw you want to make sure the on/off switch is NOT making contact when it is in the run position. The switch needs to be OPEN for the saw to run, closing the switch basically grounds the sparkplug out, preventing ignition.

Zebrafive · Jun 25, 2019

John_Mc said:
Actually, on a chainsaw you want to make sure the on/off switch is NOT making good contact. The switch needs to be OPEN for the saw to run, closing the switch basically grounds the sparkplug out, preventing ignition.

Agreed, just disconnect the wire to the switch and make sure it does not short to ground and test for spark.
Also make sure the exhaust muffler is tight (nothing to do with no spark, just another problem these saws have)

RNeumann · Jun 25, 2019

An electric switch, by design, is opening and closing a set of contacts. So testing the switch function and wiring would be a part of my diagnosis before ordering a new coil.

/pine · Jun 25, 2019

most coils can be tested at quality repair shops...bad coils may still put out a spark (sometimes) but may not necessarily be at the right time etc...

There have been other threads where similar issues with coils have been discussed...