no spark

[amiga]

I have an old McCulloch MS1635 chainsaw. This has no points. I lost spark. I removed ground wire from coil and tested with spark tester and have no spark. I cleaned magnet surfaces on flywheel and set gap from flywheel to coil. I sanded clean the surfaces between coil mounts and coil housing. I got a coil off ebay that was supposed to be new, but looked like it had been thru a war. It didn't work. I sent it back and found a new coil on Amazon. This one looked like a new coil. Still no spark. I ohmed it out and got 2.8k from spar plug terminal to coil housing and same from spark plug terminal to spade terminal. I got 3.8 form spade to housing. I am unable to find any specs to tell me if this is normal readings. When i test for spark I plugged in spark tester and had a jumper wire from spark plug to ground and a wire from ground to coil housing. Anyone know if these reading are normal or any ideas on what I missed. Thank you for your time.

 

[Bob Hedgecutter]

As per usual with these wee saws, I will admit to having very little knowledge on them and I also do not test coils with multi meters- so cannot help you much there.
Checks for most any saw I can suggest though.

Was your lack of spark gradual- or instant? Was the saw previously running irradicably, or running from cold and then gradually petering out, would not restart until it had cooled down?
Do the fly wheel magnets still hold a largish screwdriver?
Is the air gap between the coil and flywheel about tight business card width?

I would disconnect all wiring except for the original coil to ground (plastic case so does not ground through coil mount screw) after ensuring continuity of that ground wire and good connections- and the HT wire to the plug (brand new plug would be good) and test that alone with a known good tester between plug and lead as the simplest form of a circuit.

I would be asking questions of the flywheel if 3 coils correctly fitted gain the same no spark result and possibly the HT lead to plug connection of the original coil, or faults in the HT wire- but this is unlikely in 3 coils.

Sorry I cannot be of more help.

 

[Bob Hedgecutter]

I have an old McCulloch MS1635 chainsaw. This has no points. I lost spark. I removed ground wire from coil and tested with spark tester and have no spark. I cleaned magnet surfaces on flywheel and set gap from flywheel to coil. I sanded clean the surfaces between coil mounts and coil housing. I got a coil off ebay that was supposed to be new, but looked like it had been thru a war. It didn't work. I sent it back and found a new coil on Amazon. This one looked like a new coil. Still no spark. I ohmed it out and got 2.8k from spar plug terminal to coil housing and same from spark plug terminal to spade terminal. I got 3.8 form spade to housing. I am unable to find any specs to tell me if this is normal readings. When i test for spark I plugged in spark tester and had a jumper wire from spark plug to ground and a wire from ground to coil housing. Anyone know if these reading are normal or any ideas on what I missed. Thank you for your time.

Did you have any luck gaining any spark in this saw yet?

 

[amiga]

Nothing yet. For some reason my reply to you vanished. I find it hard to believe that 3 coils are bad. Can't come up with much else. I did see where someone reduced the gap to flywheel and it worked for them. I'll give it a try and let you know. Thank you for your response.

 

[amiga]

Nothing yet. For some reason my reply to you vanished. I find it hard to believe that 3 coils are bad. Can't come up with much else. I did see where someone reduced the gap to flywheel and it worked for them. I'll give it a try and let you know. Thank you for your response.

I tried reducing the gap. No luck.

 

[Bob Hedgecutter]

Air gap between coil and flywheel should be a business card when the magnets are in contact with the loose coil.

Do the magnets still hold a medium sized screwdriver?

I would be suspecting the feed wire from coil to kill switch/faulty switch, if that wire is earthing before the switch it will kill the live circuit, the equivalent of trying to start the saw with the switch in the off position.

 

[amiga]

I gapped with business card and the magnets hold screwdriver. I tested with kill switch wire disconnected. Counting the original coil then the one from ebay I sent back and now this one from Amazon, this makes 3. I doubt that all three are bad, but just don't know what else could be going on.

 

[Bob Hedgecutter]

You tested the kill switch by disconnecting the return wire?
This does not find a fault in the feed wire to the switch- if you can disconnect that at the switch and trace it back to the coil, you might find a fault.
Or disconnect at switch and check for spark- if the switch is broken, this will prove/disprove such.

 

[amiga]

I disconnected the wire from the spade terminal on coil to switch isolating the coil. Still no spark.

 

[Bob Hedgecutter]

So all 3 coils- no spark with the kill switch eliminated.
Same spark plug during the entire testing phase?

Brand new or known good plug should be the first port of call, because even if timed incorrectly, a good flywheel at correct speed passing a good coil will create spark. If it is not the coil/coils, not the plug- then it kind of has to be the flywheel.

 

[amiga]

Spark plug is new. I even tried a known good plug. I have a spark tester that I use. I tested it on another machine. I agree that the flywheel is all that's left, but magnets are strong and clean. I even ran jumper from plug housing to coil housing to ensure a good ground path.

 

[Bob Hedgecutter]

Incidentally-how are you spinning the flywheel to induce spark?
With a drill or with the recoil starter?

 

[amiga]

I'm using a drill with a socket on it to turn flywheel.
I also set recoil cover on to use it to test.

 

[Bob Hedgecutter]

Drill turning in correct direction?
Drill speed fast enough to educe spark?

 

[amiga]

Correct rotation is counter-clockwise so I set drill to reverse. Drill spins very fast. Also tried with recoil.

 

[amiga]

I gave up. I gave it away and bought an old Stihl from my neighbor. Runs great!

 

[Bob Hedgecutter]

Often easier with those little rebellious consumer saws.

 

[amiga]

$50 well spent.