lawnmowertech37
Addicted to ArboristSite
thats good to know you have some i will keep that in mind if i get any one looking for some
Mcculloch Pro Mac 800
- Thread starter Degull
- Start date
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thats good to know you have some i will keep that in mind if i get any one looking for some
did you check to see if you have a points system,,, if so clean and reset the points, as was posted before,,,, also, did you try to start the saw without connecting the kill switch wires?? it may be as simple as that...if it fires, check teh wires for cracks that could short out teh coil....
Degull
ArboristSite Lurker
Just checked behind the flywheel and there are no wires. Had a good look with a flash light and inspection mirror and there are no points. Measured resistance between the spark plug end and the GND and SW terminals. Reading 2.4k Ohms on both terminals. I pretty sure that the coil is bad. I can't see how the coil could work if the SW terminal is always short to ground.
Degull
ArboristSite Lurker
Lawnmowertech37 check your pms. I messaged you about a coil. Thanks.
Saw Dr.
Junk Collector
A coil is just that. A coil of wire. You could wind your own if you knew the specs. Yes it is shorted, it is just a piece of wire! Well, two actually, a primary circuit, and a secondary circuit. Have you tried to run it with the ignition kill wire disconnected yet? Your coil may be bad, but I'd exhaust all options before throwing down for a new one.
lawnmowertech37
Addicted to ArboristSite
b200 is correct need to see if we can fix the issue could be a bent wire somewhere in the system do some trouble shooting first the good news is you know where the coils are available
im not in no big hurry take your time rule everything out as a source such as the wires on the stop switch etc.
another thing it could be is the Spark plug boot could be bad
or disconnected if that is the case they are available in expensive
like $ 4.00 shipping plus 1.00 for the boot then again spark plugs itself can go bad with a bad diode in the plug
i would feel bad that you pay the price on the new coil and you get the coil and find out it is not a coil issue
so lets make sure of the problem first at least im looking out for you here
Degull
ArboristSite Lurker
Yes I've tried to run it without the kill wire connected. Still no spark. Thanks for the suggestion.
Saw Dr.
Junk Collector
Right on, Calvin! Remove the cap, and see if you get spark from the wire to ground. If you do not, you're probably going to have to bite the bullet.
Degull
ArboristSite Lurker
The boot was removed or pulled back and I'm using a new spark plug.
HimWill
Addicted to ArboristSite
Did you check the coil to flywheel gap,it must be correct for you to get a spark? Re-install the coil and gap it properly,then check for spark.
Sounds like this saw has been apart a time or two before you got it,so gap the coil properly before you call the coil bad.
Sounds like this saw has been apart a time or two before you got it,so gap the coil properly before you call the coil bad.
Degull
ArboristSite Lurker
I did not check the coil/flywheel gap. I have no idea what it should be?
HimWill
Addicted to ArboristSite
The third picture you posted shows the coil core as being shiny.That would indicate it is rubbing the flywheel.You will get no spark unless you set the gap between the coil and the flywheel.The "down and dirty" way is to take a standard business card and place it between the magnets on the flywheel and the coil.Let the magnets pull the coil to it with the card spacing them apart.Tighten the coil down tight and turn the flywheel to remove the card,it will be tight against the flywheel.You should then have a gap between the coil and flywheel as you rotate the flywheel.Now spin it over and check for a spark.
lawnmowertech37
Addicted to ArboristSite
well on a tecumseh 4 stroke its between .010 and .014 thousands on a feeler gauge
Biker Dude
Addicted to ArboristSite
It is supposed to be 12 thou. which is equal to 3 standard sheets of paper using the "business card" method.
What you are reading is the resistance of the primary windings, which is pretty low so it appears as a short circuit. 2.4K Ohms on the secondary seems O.K. If your saw is electronic ignition (no points) then the trigger in the coil must be gone. Sometimes you can use one of the aftermarket point replacement modules to trigger the coil but likely as not you will have to replace the entire coil.
Mark
Degull
ArboristSite Lurker
Thanks for posting that fluke sheet on how to troubleshoot ignitions. Let me ask a question, I don't quite understand how the SW terminal fits in. The motor is shut off when the SW is grounded. Where does it fit in when it comes to the primary and secondary winding? Your right about the SW and the GND not being shorted. It's reading 22 Ohms. When I first checked I was using the beeper on the meter to check continuity. I'm quessing the gnd terminal is the tap between the primary and secondary winding. Thanks for helping understand these iginitions!
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Degull
ArboristSite Lurker
Whoops, sorry, I thought that I posted the results after the gap was set. No luck. I used a credit card to set the gap between the coil and the flywheel. Still no spark.
Saw Dr.
Junk Collector
Credit card is WAAAYYY too thick. Use a business card, or the cover from a pack of matches. Disconnect the SW terminal, and remove the spark plug cap. Hold the end of the wire about 1/8" from a grounded surface (cooling fin of engine) and rift on the cord to see if you get a spark. You have to spin it pretty good. There is a cut-in speed on those electronic coils.
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